| Message ID | 20211015024658.1353987-3-xianting.tian@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | make hvc pass dma capable memory to its backend | expand |
| Related | show |
Hi Greg and experts Is this version ok for you? thanks 在 2021/10/15 上午10:46, Xianting Tian 写道: > As well known, hvc backend can register its opertions to hvc backend. > the operations contain put_chars(), get_chars() and so on. > > Some hvc backend may do dma in its operations. eg, put_chars() of > virtio-console. But in the code of hvc framework, it may pass DMA > incapable memory to put_chars() under a specific configuration, which > is explained in commit c4baad5029(virtio-console: avoid DMA from stack): > 1, c[] is on stack, > hvc_console_print(): > char c[N_OUTBUF] __ALIGNED__; > cons_ops[index]->put_chars(vtermnos[index], c, i); > 2, ch is on stack, > static void hvc_poll_put_char(,,char ch) > { > struct tty_struct *tty = driver->ttys[0]; > struct hvc_struct *hp = tty->driver_data; > int n; > > do { > n = hp->ops->put_chars(hp->vtermno, &ch, 1); > } while (n <= 0); > } > > Commit c4baad5029 is just the fix to avoid DMA from stack memory, which > is passed to virtio-console by hvc framework in above code. But I think > the fix is aggressive, it directly uses kmemdup() to alloc new buffer > from kmalloc area and do memcpy no matter the memory is in kmalloc area > or not. But most importantly, it should better be fixed in the hvc > framework, by changing it to never pass stack memory to the put_chars() > function in the first place. Otherwise, we still face the same issue if > a new hvc backend using dma added in the furture. > > In this patch, add 'char cons_outbuf[]' as part of 'struct hvc_struct', > so hp->cons_outbuf is no longer the stack memory, we can use it in above > cases safely. We also add lock to protect cons_outbuf instead of using > the global lock of hvc. > > Introduce another array(cons_hvcs[]) for hvc pointers next to the > cons_ops[] and vtermnos[] arrays. With the array, we can easily find > hvc's cons_outbuf and its lock. > > With the patch, we can revert the fix c4baad5029. > > Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com> > Signed-off-by: Shile Zhang <shile.zhang@linux.alibaba.com> > --- > drivers/tty/hvc/hvc_console.c | 36 ++++++++++++++++++++--------------- > drivers/tty/hvc/hvc_console.h | 21 +++++++++++++++++++- > 2 files changed, 41 insertions(+), 16 deletions(-) > > diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c > index 5957ab728..11f2463a1 100644 > --- a/drivers/tty/hvc/hvc_console.c > +++ b/drivers/tty/hvc/hvc_console.c > @@ -41,16 +41,6 @@ > */ > #define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */ > > -/* > - * These sizes are most efficient for vio, because they are the > - * native transfer size. We could make them selectable in the > - * future to better deal with backends that want other buffer sizes. > - */ > -#define N_OUTBUF 16 > -#define N_INBUF 16 > - > -#define __ALIGNED__ __attribute__((__aligned__(L1_CACHE_BYTES))) > - > static struct tty_driver *hvc_driver; > static struct task_struct *hvc_task; > > @@ -142,6 +132,7 @@ static int hvc_flush(struct hvc_struct *hp) > static const struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES]; > static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] = > {[0 ... MAX_NR_HVC_CONSOLES - 1] = -1}; > +static struct hvc_struct *cons_hvcs[MAX_NR_HVC_CONSOLES]; > > /* > * Console APIs, NOT TTY. These APIs are available immediately when > @@ -151,9 +142,11 @@ static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] = > static void hvc_console_print(struct console *co, const char *b, > unsigned count) > { > - char c[N_OUTBUF] __ALIGNED__; > + char *c; > unsigned i = 0, n = 0; > int r, donecr = 0, index = co->index; > + unsigned long flags; > + struct hvc_struct *hp; > > /* Console access attempt outside of acceptable console range. */ > if (index >= MAX_NR_HVC_CONSOLES) > @@ -163,6 +156,13 @@ static void hvc_console_print(struct console *co, const char *b, > if (vtermnos[index] == -1) > return; > > + hp = cons_hvcs[index]; > + if (!hp) > + return; > + > + c = hp->cons_outbuf; > + > + spin_lock_irqsave(&hp->cons_outbuf_lock, flags); > while (count > 0 || i > 0) { > if (count > 0 && i < sizeof(c)) { > if (b[n] == '\n' && !donecr) { > @@ -191,6 +191,7 @@ static void hvc_console_print(struct console *co, const char *b, > } > } > } > + spin_unlock_irqrestore(&hp->cons_outbuf_lock, flags); > hvc_console_flush(cons_ops[index], vtermnos[index]); > } > > @@ -878,9 +879,13 @@ static void hvc_poll_put_char(struct tty_driver *driver, int line, char ch) > struct tty_struct *tty = driver->ttys[0]; > struct hvc_struct *hp = tty->driver_data; > int n; > + unsigned long flags; > > do { > - n = hp->ops->put_chars(hp->vtermno, &ch, 1); > + spin_lock_irqsave(&hp->cons_outbuf_lock, flags); > + hp->cons_outbuf[0] = ch; > + n = hp->ops->put_chars(hp->vtermno, &hp->cons_outbuf[0], 1); > + spin_unlock_irqrestore(&hp->cons_outbuf_lock, flags); > } while (n <= 0); > } > #endif > @@ -922,8 +927,7 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data, > return ERR_PTR(err); > } > > - hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size, > - GFP_KERNEL); > + hp = kzalloc(struct_size(hp, outbuf, outbuf_size), GFP_KERNEL); > if (!hp) > return ERR_PTR(-ENOMEM); > > @@ -931,13 +935,13 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data, > hp->data = data; > hp->ops = ops; > hp->outbuf_size = outbuf_size; > - hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))]; > > tty_port_init(&hp->port); > hp->port.ops = &hvc_port_ops; > > INIT_WORK(&hp->tty_resize, hvc_set_winsz); > spin_lock_init(&hp->lock); > + spin_lock_init(&hp->cons_outbuf_lock); > mutex_lock(&hvc_structs_mutex); > > /* > @@ -964,6 +968,7 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data, > if (i < MAX_NR_HVC_CONSOLES) { > cons_ops[i] = ops; > vtermnos[i] = vtermno; > + cons_hvcs[i] = hp; > } > > list_add_tail(&(hp->next), &hvc_structs); > @@ -988,6 +993,7 @@ int hvc_remove(struct hvc_struct *hp) > if (hp->index < MAX_NR_HVC_CONSOLES) { > vtermnos[hp->index] = -1; > cons_ops[hp->index] = NULL; > + cons_hvcs[hp->index] = NULL; > } > > /* Don't whack hp->irq because tty_hangup() will need to free the irq. */ > diff --git a/drivers/tty/hvc/hvc_console.h b/drivers/tty/hvc/hvc_console.h > index 18d005814..2c32ab67b 100644 > --- a/drivers/tty/hvc/hvc_console.h > +++ b/drivers/tty/hvc/hvc_console.h > @@ -32,12 +32,21 @@ > */ > #define HVC_ALLOC_TTY_ADAPTERS 8 > > +/* > + * These sizes are most efficient for vio, because they are the > + * native transfer size. We could make them selectable in the > + * future to better deal with backends that want other buffer sizes. > + */ > +#define N_OUTBUF 16 > +#define N_INBUF 16 > + > +#define __ALIGNED__ __attribute__((__aligned__(L1_CACHE_BYTES))) > + > struct hvc_struct { > struct tty_port port; > spinlock_t lock; > int index; > int do_wakeup; > - char *outbuf; > int outbuf_size; > int n_outbuf; > uint32_t vtermno; > @@ -48,6 +57,16 @@ struct hvc_struct { > struct work_struct tty_resize; > struct list_head next; > unsigned long flags; > + > + /* > + * the buf and its lock are used in hvc console api for putting chars, > + * and also used in hvc_poll_put_char() for putting single char. > + */ > + spinlock_t cons_outbuf_lock; > + char cons_outbuf[N_OUTBUF] __ALIGNED__; > + > + /* the buf is used for putting chars to tty */ > + char outbuf[] __ALIGNED__; > }; > > /* implemented by a low level driver */
hi Greg， Could I get your comments of this new version patches？ thanks 在 2021/10/15 上午10:46, Xianting Tian 写道: > As well known, hvc backend can register its opertions to hvc backend. > the operations contain put_chars(), get_chars() and so on. > > Some hvc backend may do dma in its operations. eg, put_chars() of > virtio-console. But in the code of hvc framework, it may pass DMA > incapable memory to put_chars() under a specific configuration, which > is explained in commit c4baad5029(virtio-console: avoid DMA from stack): > 1, c[] is on stack, > hvc_console_print(): > char c[N_OUTBUF] __ALIGNED__; > cons_ops[index]->put_chars(vtermnos[index], c, i); > 2, ch is on stack, > static void hvc_poll_put_char(,,char ch) > { > struct tty_struct *tty = driver->ttys[0]; > struct hvc_struct *hp = tty->driver_data; > int n; > > do { > n = hp->ops->put_chars(hp->vtermno, &ch, 1); > } while (n <= 0); > } > > Commit c4baad5029 is just the fix to avoid DMA from stack memory, which > is passed to virtio-console by hvc framework in above code. But I think > the fix is aggressive, it directly uses kmemdup() to alloc new buffer > from kmalloc area and do memcpy no matter the memory is in kmalloc area > or not. But most importantly, it should better be fixed in the hvc > framework, by changing it to never pass stack memory to the put_chars() > function in the first place. Otherwise, we still face the same issue if > a new hvc backend using dma added in the furture. > > In this patch, add 'char cons_outbuf[]' as part of 'struct hvc_struct', > so hp->cons_outbuf is no longer the stack memory, we can use it in above > cases safely. We also add lock to protect cons_outbuf instead of using > the global lock of hvc. > > Introduce another array(cons_hvcs[]) for hvc pointers next to the > cons_ops[] and vtermnos[] arrays. With the array, we can easily find > hvc's cons_outbuf and its lock. > > With the patch, we can revert the fix c4baad5029. > > Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com> > Signed-off-by: Shile Zhang <shile.zhang@linux.alibaba.com> > --- > drivers/tty/hvc/hvc_console.c | 36 ++++++++++++++++++++--------------- > drivers/tty/hvc/hvc_console.h | 21 +++++++++++++++++++- > 2 files changed, 41 insertions(+), 16 deletions(-) > > diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c > index 5957ab728..11f2463a1 100644 > --- a/drivers/tty/hvc/hvc_console.c > +++ b/drivers/tty/hvc/hvc_console.c > @@ -41,16 +41,6 @@ > */ > #define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */ > > -/* > - * These sizes are most efficient for vio, because they are the > - * native transfer size. We could make them selectable in the > - * future to better deal with backends that want other buffer sizes. > - */ > -#define N_OUTBUF 16 > -#define N_INBUF 16 > - > -#define __ALIGNED__ __attribute__((__aligned__(L1_CACHE_BYTES))) > - > static struct tty_driver *hvc_driver; > static struct task_struct *hvc_task; > > @@ -142,6 +132,7 @@ static int hvc_flush(struct hvc_struct *hp) > static const struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES]; > static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] = > {[0 ... MAX_NR_HVC_CONSOLES - 1] = -1}; > +static struct hvc_struct *cons_hvcs[MAX_NR_HVC_CONSOLES]; > > /* > * Console APIs, NOT TTY. These APIs are available immediately when > @@ -151,9 +142,11 @@ static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] = > static void hvc_console_print(struct console *co, const char *b, > unsigned count) > { > - char c[N_OUTBUF] __ALIGNED__; > + char *c; > unsigned i = 0, n = 0; > int r, donecr = 0, index = co->index; > + unsigned long flags; > + struct hvc_struct *hp; > > /* Console access attempt outside of acceptable console range. */ > if (index >= MAX_NR_HVC_CONSOLES) > @@ -163,6 +156,13 @@ static void hvc_console_print(struct console *co, const char *b, > if (vtermnos[index] == -1) > return; > > + hp = cons_hvcs[index]; > + if (!hp) > + return; > + > + c = hp->cons_outbuf; > + > + spin_lock_irqsave(&hp->cons_outbuf_lock, flags); > while (count > 0 || i > 0) { > if (count > 0 && i < sizeof(c)) { > if (b[n] == '\n' && !donecr) { > @@ -191,6 +191,7 @@ static void hvc_console_print(struct console *co, const char *b, > } > } > } > + spin_unlock_irqrestore(&hp->cons_outbuf_lock, flags); > hvc_console_flush(cons_ops[index], vtermnos[index]); > } > > @@ -878,9 +879,13 @@ static void hvc_poll_put_char(struct tty_driver *driver, int line, char ch) > struct tty_struct *tty = driver->ttys[0]; > struct hvc_struct *hp = tty->driver_data; > int n; > + unsigned long flags; > > do { > - n = hp->ops->put_chars(hp->vtermno, &ch, 1); > + spin_lock_irqsave(&hp->cons_outbuf_lock, flags); > + hp->cons_outbuf[0] = ch; > + n = hp->ops->put_chars(hp->vtermno, &hp->cons_outbuf[0], 1); > + spin_unlock_irqrestore(&hp->cons_outbuf_lock, flags); > } while (n <= 0); > } > #endif > @@ -922,8 +927,7 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data, > return ERR_PTR(err); > } > > - hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size, > - GFP_KERNEL); > + hp = kzalloc(struct_size(hp, outbuf, outbuf_size), GFP_KERNEL); > if (!hp) > return ERR_PTR(-ENOMEM); > > @@ -931,13 +935,13 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data, > hp->data = data; > hp->ops = ops; > hp->outbuf_size = outbuf_size; > - hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))]; > > tty_port_init(&hp->port); > hp->port.ops = &hvc_port_ops; > > INIT_WORK(&hp->tty_resize, hvc_set_winsz); > spin_lock_init(&hp->lock); > + spin_lock_init(&hp->cons_outbuf_lock); > mutex_lock(&hvc_structs_mutex); > > /* > @@ -964,6 +968,7 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data, > if (i < MAX_NR_HVC_CONSOLES) { > cons_ops[i] = ops; > vtermnos[i] = vtermno; > + cons_hvcs[i] = hp; > } > > list_add_tail(&(hp->next), &hvc_structs); > @@ -988,6 +993,7 @@ int hvc_remove(struct hvc_struct *hp) > if (hp->index < MAX_NR_HVC_CONSOLES) { > vtermnos[hp->index] = -1; > cons_ops[hp->index] = NULL; > + cons_hvcs[hp->index] = NULL; > } > > /* Don't whack hp->irq because tty_hangup() will need to free the irq. */ > diff --git a/drivers/tty/hvc/hvc_console.h b/drivers/tty/hvc/hvc_console.h > index 18d005814..2c32ab67b 100644 > --- a/drivers/tty/hvc/hvc_console.h > +++ b/drivers/tty/hvc/hvc_console.h > @@ -32,12 +32,21 @@ > */ > #define HVC_ALLOC_TTY_ADAPTERS 8 > > +/* > + * These sizes are most efficient for vio, because they are the > + * native transfer size. We could make them selectable in the > + * future to better deal with backends that want other buffer sizes. > + */ > +#define N_OUTBUF 16 > +#define N_INBUF 16 > + > +#define __ALIGNED__ __attribute__((__aligned__(L1_CACHE_BYTES))) > + > struct hvc_struct { > struct tty_port port; > spinlock_t lock; > int index; > int do_wakeup; > - char *outbuf; > int outbuf_size; > int n_outbuf; > uint32_t vtermno; > @@ -48,6 +57,16 @@ struct hvc_struct { > struct work_struct tty_resize; > struct list_head next; > unsigned long flags; > + > + /* > + * the buf and its lock are used in hvc console api for putting chars, > + * and also used in hvc_poll_put_char() for putting single char. > + */ > + spinlock_t cons_outbuf_lock; > + char cons_outbuf[N_OUTBUF] __ALIGNED__; > + > + /* the buf is used for putting chars to tty */ > + char outbuf[] __ALIGNED__; > }; > > /* implemented by a low level driver */
A: http://en.wikipedia.org/wiki/Top_post Q: Were do I find info about this thing called top-posting? A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail? A: No. Q: Should I include quotations after my reply? http://daringfireball.net/2007/07/on_top On Wed, Oct 20, 2021 at 04:47:23PM +0800, Xianting Tian wrote: > hi Greg， > > Could I get your comments of this new version patches？ thanks It has been less than 5 days. Please relax, and only worry after 2 weeks have gone by. We have lots of patches to review. To help maintainers out, why don't you review other patches on the mailing lists as well while you wait? thanks, greg k-h
On 15. 10. 21, 4:46, Xianting Tian wrote: > @@ -151,9 +142,11 @@ static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] = > static void hvc_console_print(struct console *co, const char *b, > unsigned count) > { > - char c[N_OUTBUF] __ALIGNED__; > + char *c; > unsigned i = 0, n = 0; > int r, donecr = 0, index = co->index; > + unsigned long flags; > + struct hvc_struct *hp; > > /* Console access attempt outside of acceptable console range. */ > if (index >= MAX_NR_HVC_CONSOLES) > @@ -163,6 +156,13 @@ static void hvc_console_print(struct console *co, const char *b, > if (vtermnos[index] == -1) > return; > > + hp = cons_hvcs[index]; > + if (!hp) > + return; You effectively make the console unusable until someone calls hvc_alloc() for this device, correct? This doesn't look right. Neither you describe this change of behaviour in the commit log. regards,
在 2021/10/26 下午1:10, Jiri Slaby 写道: > On 15. 10. 21, 4:46, Xianting Tian wrote: >> @@ -151,9 +142,11 @@ static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] = >> static void hvc_console_print(struct console *co, const char *b, >> unsigned count) >> { >> - char c[N_OUTBUF] __ALIGNED__; >> + char *c; >> unsigned i = 0, n = 0; >> int r, donecr = 0, index = co->index; >> + unsigned long flags; >> + struct hvc_struct *hp; >> /* Console access attempt outside of acceptable console >> range. */ >> if (index >= MAX_NR_HVC_CONSOLES) >> @@ -163,6 +156,13 @@ static void hvc_console_print(struct console >> *co, const char *b, >> if (vtermnos[index] == -1) >> return; >> + hp = cons_hvcs[index]; >> + if (!hp) >> + return; > > You effectively make the console unusable until someone calls > hvc_alloc() for this device, correct? This doesn't look right. Neither > you describe this change of behaviour in the commit log. I mentioned such info in the commit log: 'Introduce another array(cons_hvcs[]) for hvc pointers next to the cons_ops[] and vtermnos[] arrays. With the array, we can easily find hvc's cons_outbuf and its lock.' After you pointed it out, I just found what you said make sense, I checked the code hvc_console_print() can support print before hvc_alloc() is called when someone use hvc_instantiate() for an early console discovery method. I send a patch to fix the issue? or these serial pathches reverted fisrtly then I resend new version patches? thanks > > regards,
On Tue, Oct 26, 2021 at 02:02:21PM +0800, Xianting Tian wrote: > 在 2021/10/26 下午1:10, Jiri Slaby 写道: > > On 15. 10. 21, 4:46, Xianting Tian wrote: > > > @@ -151,9 +142,11 @@ static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] = > > > static void hvc_console_print(struct console *co, const char *b, > > > unsigned count) > > > { > > > - char c[N_OUTBUF] __ALIGNED__; > > > + char *c; > > > unsigned i = 0, n = 0; > > > int r, donecr = 0, index = co->index; > > > + unsigned long flags; > > > + struct hvc_struct *hp; > > > /* Console access attempt outside of acceptable console > > > range. */ > > > if (index >= MAX_NR_HVC_CONSOLES) > > > @@ -163,6 +156,13 @@ static void hvc_console_print(struct console > > > *co, const char *b, > > > if (vtermnos[index] == -1) > > > return; > > > + hp = cons_hvcs[index]; > > > + if (!hp) > > > + return; > > > > You effectively make the console unusable until someone calls > > hvc_alloc() for this device, correct? This doesn't look right. Neither > > you describe this change of behaviour in the commit log. > > I mentioned such info in the commit log: > 'Introduce another array(cons_hvcs[]) for hvc pointers next to the > cons_ops[] and vtermnos[] arrays. With the array, we can easily find > hvc's cons_outbuf and its lock.' > > After you pointed it out, I just found what you said make sense, I checked the code hvc_console_print() can support print before hvc_alloc() is called when someone use hvc_instantiate() for an early console discovery method. > I send a patch to fix the issue? or these serial pathches reverted fisrtly then I resend new version patches? thanks Let me revert these now and you can send an updated version. thanks, greg k-h
在 2021/10/26 下午2:10, Greg KH 写道: > On Tue, Oct 26, 2021 at 02:02:21PM +0800, Xianting Tian wrote: >> 在 2021/10/26 下午1:10, Jiri Slaby 写道: >>> On 15. 10. 21, 4:46, Xianting Tian wrote: >>>> @@ -151,9 +142,11 @@ static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] = >>>> static void hvc_console_print(struct console *co, const char *b, >>>> unsigned count) >>>> { >>>> - char c[N_OUTBUF] __ALIGNED__; >>>> + char *c; >>>> unsigned i = 0, n = 0; >>>> int r, donecr = 0, index = co->index; >>>> + unsigned long flags; >>>> + struct hvc_struct *hp; >>>> /* Console access attempt outside of acceptable console >>>> range. */ >>>> if (index >= MAX_NR_HVC_CONSOLES) >>>> @@ -163,6 +156,13 @@ static void hvc_console_print(struct console >>>> *co, const char *b, >>>> if (vtermnos[index] == -1) >>>> return; >>>> + hp = cons_hvcs[index]; >>>> + if (!hp) >>>> + return; >>> You effectively make the console unusable until someone calls >>> hvc_alloc() for this device, correct? This doesn't look right. Neither >>> you describe this change of behaviour in the commit log. >> I mentioned such info in the commit log: >> 'Introduce another array(cons_hvcs[]) for hvc pointers next to the >> cons_ops[] and vtermnos[] arrays. With the array, we can easily find >> hvc's cons_outbuf and its lock.' >> >> After you pointed it out, I just found what you said make sense, I checked the code hvc_console_print() can support print before hvc_alloc() is called when someone use hvc_instantiate() for an early console discovery method. >> I send a patch to fix the issue? or these serial pathches reverted fisrtly then I resend new version patches? thanks > Let me revert these now and you can send an updated version. OK, thanks. > > thanks, > > greg k-h
On Tue, Oct 26, 2021 at 02:11:51PM +0800, Xianting Tian wrote: > > 在 2021/10/26 下午2:10, Greg KH 写道: > > On Tue, Oct 26, 2021 at 02:02:21PM +0800, Xianting Tian wrote: > > > 在 2021/10/26 下午1:10, Jiri Slaby 写道: > > > > On 15. 10. 21, 4:46, Xianting Tian wrote: > > > > > @@ -151,9 +142,11 @@ static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] = > > > > > static void hvc_console_print(struct console *co, const char *b, > > > > > unsigned count) > > > > > { > > > > > - char c[N_OUTBUF] __ALIGNED__; > > > > > + char *c; > > > > > unsigned i = 0, n = 0; > > > > > int r, donecr = 0, index = co->index; > > > > > + unsigned long flags; > > > > > + struct hvc_struct *hp; > > > > > /* Console access attempt outside of acceptable console > > > > > range. */ > > > > > if (index >= MAX_NR_HVC_CONSOLES) > > > > > @@ -163,6 +156,13 @@ static void hvc_console_print(struct console > > > > > *co, const char *b, > > > > > if (vtermnos[index] == -1) > > > > > return; > > > > > + hp = cons_hvcs[index]; > > > > > + if (!hp) > > > > > + return; > > > > You effectively make the console unusable until someone calls > > > > hvc_alloc() for this device, correct? This doesn't look right. Neither > > > > you describe this change of behaviour in the commit log. > > > I mentioned such info in the commit log: > > > 'Introduce another array(cons_hvcs[]) for hvc pointers next to the > > > cons_ops[] and vtermnos[] arrays. With the array, we can easily find > > > hvc's cons_outbuf and its lock.' > > > > > > After you pointed it out, I just found what you said make sense, I checked the code hvc_console_print() can support print before hvc_alloc() is called when someone use hvc_instantiate() for an early console discovery method. > > > I send a patch to fix the issue? or these serial pathches reverted fisrtly then I resend new version patches? thanks > > Let me revert these now and you can send an updated version. > OK, thanks. I have now reverted patches 2/3 and 3/3 in this series from my tree. The first patch was just fine. thanks, greg k-h
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c index 5957ab728..11f2463a1 100644 --- a/drivers/tty/hvc/hvc_console.c +++ b/drivers/tty/hvc/hvc_console.c @@ -41,16 +41,6 @@ */ #define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */ -/* - * These sizes are most efficient for vio, because they are the - * native transfer size. We could make them selectable in the - * future to better deal with backends that want other buffer sizes. - */ -#define N_OUTBUF 16 -#define N_INBUF 16 - -#define __ALIGNED__ __attribute__((__aligned__(L1_CACHE_BYTES))) - static struct tty_driver *hvc_driver; static struct task_struct *hvc_task; @@ -142,6 +132,7 @@ static int hvc_flush(struct hvc_struct *hp) static const struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES]; static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] = {[0 ... MAX_NR_HVC_CONSOLES - 1] = -1}; +static struct hvc_struct *cons_hvcs[MAX_NR_HVC_CONSOLES]; /* * Console APIs, NOT TTY. These APIs are available immediately when @@ -151,9 +142,11 @@ static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] = static void hvc_console_print(struct console *co, const char *b, unsigned count) { - char c[N_OUTBUF] __ALIGNED__; + char *c; unsigned i = 0, n = 0; int r, donecr = 0, index = co->index; + unsigned long flags; + struct hvc_struct *hp; /* Console access attempt outside of acceptable console range. */ if (index >= MAX_NR_HVC_CONSOLES) @@ -163,6 +156,13 @@ static void hvc_console_print(struct console *co, const char *b, if (vtermnos[index] == -1) return; + hp = cons_hvcs[index]; + if (!hp) + return; + + c = hp->cons_outbuf; + + spin_lock_irqsave(&hp->cons_outbuf_lock, flags); while (count > 0 || i > 0) { if (count > 0 && i < sizeof(c)) { if (b[n] == '\n' && !donecr) { @@ -191,6 +191,7 @@ static void hvc_console_print(struct console *co, const char *b, } } } + spin_unlock_irqrestore(&hp->cons_outbuf_lock, flags); hvc_console_flush(cons_ops[index], vtermnos[index]); } @@ -878,9 +879,13 @@ static void hvc_poll_put_char(struct tty_driver *driver, int line, char ch) struct tty_struct *tty = driver->ttys[0]; struct hvc_struct *hp = tty->driver_data; int n; + unsigned long flags; do { - n = hp->ops->put_chars(hp->vtermno, &ch, 1); + spin_lock_irqsave(&hp->cons_outbuf_lock, flags); + hp->cons_outbuf[0] = ch; + n = hp->ops->put_chars(hp->vtermno, &hp->cons_outbuf[0], 1); + spin_unlock_irqrestore(&hp->cons_outbuf_lock, flags); } while (n <= 0); } #endif @@ -922,8 +927,7 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data, return ERR_PTR(err); } - hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size, - GFP_KERNEL); + hp = kzalloc(struct_size(hp, outbuf, outbuf_size), GFP_KERNEL); if (!hp) return ERR_PTR(-ENOMEM); @@ -931,13 +935,13 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data, hp->data = data; hp->ops = ops; hp->outbuf_size = outbuf_size; - hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))]; tty_port_init(&hp->port); hp->port.ops = &hvc_port_ops; INIT_WORK(&hp->tty_resize, hvc_set_winsz); spin_lock_init(&hp->lock); + spin_lock_init(&hp->cons_outbuf_lock); mutex_lock(&hvc_structs_mutex); /* @@ -964,6 +968,7 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data, if (i < MAX_NR_HVC_CONSOLES) { cons_ops[i] = ops; vtermnos[i] = vtermno; + cons_hvcs[i] = hp; } list_add_tail(&(hp->next), &hvc_structs); @@ -988,6 +993,7 @@ int hvc_remove(struct hvc_struct *hp) if (hp->index < MAX_NR_HVC_CONSOLES) { vtermnos[hp->index] = -1; cons_ops[hp->index] = NULL; + cons_hvcs[hp->index] = NULL; } /* Don't whack hp->irq because tty_hangup() will need to free the irq. */ diff --git a/drivers/tty/hvc/hvc_console.h b/drivers/tty/hvc/hvc_console.h index 18d005814..2c32ab67b 100644 --- a/drivers/tty/hvc/hvc_console.h +++ b/drivers/tty/hvc/hvc_console.h @@ -32,12 +32,21 @@ */ #define HVC_ALLOC_TTY_ADAPTERS 8 +/* + * These sizes are most efficient for vio, because they are the + * native transfer size. We could make them selectable in the + * future to better deal with backends that want other buffer sizes. + */ +#define N_OUTBUF 16 +#define N_INBUF 16 + +#define __ALIGNED__ __attribute__((__aligned__(L1_CACHE_BYTES))) + struct hvc_struct { struct tty_port port; spinlock_t lock; int index; int do_wakeup; - char *outbuf; int outbuf_size; int n_outbuf; uint32_t vtermno; @@ -48,6 +57,16 @@ struct hvc_struct { struct work_struct tty_resize; struct list_head next; unsigned long flags; + + /* + * the buf and its lock are used in hvc console api for putting chars, + * and also used in hvc_poll_put_char() for putting single char. + */ + spinlock_t cons_outbuf_lock; + char cons_outbuf[N_OUTBUF] __ALIGNED__; + + /* the buf is used for putting chars to tty */ + char outbuf[] __ALIGNED__; }; /* implemented by a low level driver */
As well known, hvc backend can register its opertions to hvc backend. the operations contain put_chars(), get_chars() and so on. Some hvc backend may do dma in its operations. eg, put_chars() of virtio-console. But in the code of hvc framework, it may pass DMA incapable memory to put_chars() under a specific configuration, which is explained in commit c4baad5029(virtio-console: avoid DMA from stack): 1, c[] is on stack, hvc_console_print(): char c[N_OUTBUF] __ALIGNED__; cons_ops[index]->put_chars(vtermnos[index], c, i); 2, ch is on stack, static void hvc_poll_put_char(,,char ch) { struct tty_struct *tty = driver->ttys[0]; struct hvc_struct *hp = tty->driver_data; int n; do { n = hp->ops->put_chars(hp->vtermno, &ch, 1); } while (n <= 0); } Commit c4baad5029 is just the fix to avoid DMA from stack memory, which is passed to virtio-console by hvc framework in above code. But I think the fix is aggressive, it directly uses kmemdup() to alloc new buffer from kmalloc area and do memcpy no matter the memory is in kmalloc area or not. But most importantly, it should better be fixed in the hvc framework, by changing it to never pass stack memory to the put_chars() function in the first place. Otherwise, we still face the same issue if a new hvc backend using dma added in the furture. In this patch, add 'char cons_outbuf[]' as part of 'struct hvc_struct', so hp->cons_outbuf is no longer the stack memory, we can use it in above cases safely. We also add lock to protect cons_outbuf instead of using the global lock of hvc. Introduce another array(cons_hvcs[]) for hvc pointers next to the cons_ops[] and vtermnos[] arrays. With the array, we can easily find hvc's cons_outbuf and its lock. With the patch, we can revert the fix c4baad5029. Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com> Signed-off-by: Shile Zhang <shile.zhang@linux.alibaba.com> --- drivers/tty/hvc/hvc_console.c | 36 ++++++++++++++++++++--------------- drivers/tty/hvc/hvc_console.h | 21 +++++++++++++++++++- 2 files changed, 41 insertions(+), 16 deletions(-)