Patchwork [Resend,Seabios] don't boot from un-selected devices

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Submitter Amos Kong
Date Dec. 19, 2012, 7:24 a.m.
Message ID <1355901885-24398-1-git-send-email-akong@redhat.com>
Download mbox | patch
Permalink /patch/207248/
State New
Headers show

Comments

Amos Kong - Dec. 19, 2012, 7:24 a.m.
Current seabios will try to boot from selected devices first,
if they are all failed, seabios will also try to boot from
un-selected devices.

For example:
@ qemu-kvm -boot order=n,menu=on ...

Guest will boot from network first, if it's failed, guest will try to
boot from other un-selected devices (floppy, cdrom, disk) one by one.

Sometimes, user don't want to boot from some devices. This patch changes
seabios to boot only from selected devices.

If user choose first boot device from menu, then seabios will try all
the devices, even some of them are not selected.

Signed-off-by: Amos Kong <akong@redhat.com>
---
Resend for CCing seabios maillist.
---
 src/boot.c |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)
Gerd Hoffmann - Dec. 19, 2012, 7:38 a.m.
On 12/19/12 08:24, Amos Kong wrote:
> Current seabios will try to boot from selected devices first,
> if they are all failed, seabios will also try to boot from
> un-selected devices.
> 
> For example:
> @ qemu-kvm -boot order=n,menu=on ...
> 
> Guest will boot from network first, if it's failed, guest will try to
> boot from other un-selected devices (floppy, cdrom, disk) one by one.
> 
> Sometimes, user don't want to boot from some devices. This patch changes
> seabios to boot only from selected devices.

I think (i.e. I didn't test) the patch breaks booting if the user didn't
explicitly specify a boot device.

cheers,
  Gerd
Amos Kong - Dec. 19, 2012, 8:12 a.m.
On Wed, Dec 19, 2012 at 08:38:13AM +0100, Gerd Hoffmann wrote:
> On 12/19/12 08:24, Amos Kong wrote:
> > Current seabios will try to boot from selected devices first,
> > if they are all failed, seabios will also try to boot from
> > un-selected devices.
> > 
> > For example:
> > @ qemu-kvm -boot order=n,menu=on ...
> > 
> > Guest will boot from network first, if it's failed, guest will try to
> > boot from other un-selected devices (floppy, cdrom, disk) one by one.
> > 
> > Sometimes, user don't want to boot from some devices. This patch changes
> > seabios to boot only from selected devices.
> 
> I think (i.e. I didn't test) the patch breaks booting if the user didn't
> explicitly specify a boot device.

Hi Gerd,

| #define DEFAULT_PRIO           9999

If we don't select some devices, their priority will always be 9999
 
| static int DefaultFloppyPrio = 101;
| static int DefaultCDPrio     = 102;
| static int DefaultHDPrio     = 103;
| static int DefaultBEVPrio    = 104;
 
The priority of selected devices will be changed to above values
first, the priority might be re-changed.

However, we can judge if device is selected or not by checking if the
priority is 9999.

. Boot guest without qemu boot option, guest will try to boot from
  network/hd/floppy/cdrom.

. If seabios ignores the order parameter of qemu, guest will also try
  to boot from network/hd/floppy/cdrom.
Gleb Natapov - Dec. 19, 2012, 9:32 a.m.
On Wed, Dec 19, 2012 at 03:24:45PM +0800, Amos Kong wrote:
> Current seabios will try to boot from selected devices first,
> if they are all failed, seabios will also try to boot from
> un-selected devices.
> 
> For example:
> @ qemu-kvm -boot order=n,menu=on ...
> 
> Guest will boot from network first, if it's failed, guest will try to
> boot from other un-selected devices (floppy, cdrom, disk) one by one.
> 
> Sometimes, user don't want to boot from some devices. This patch changes
And sometimes he want. The patch changes behaviour unconditionally. New
behaviour should be user selectable. Something line -boot order=strict
on qemu command line.

> seabios to boot only from selected devices.
> 
> If user choose first boot device from menu, then seabios will try all
> the devices, even some of them are not selected.
> 
> Signed-off-by: Amos Kong <akong@redhat.com>
> ---
> Resend for CCing seabios maillist.
> ---
>  src/boot.c |   13 ++++++++-----
>  1 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/src/boot.c b/src/boot.c
> index 3ca7960..ee810ac 100644
> --- a/src/boot.c
> +++ b/src/boot.c
> @@ -424,6 +424,10 @@ interactive_bootmenu(void)
>          maxmenu++;
>          printf("%d. %s\n", maxmenu
>                 , strtcpy(desc, pos->description, ARRAY_SIZE(desc)));
> +        /* If user chooses first boot device from menu, we will treat
> +	    all the devices as selected. */
> +        if (pos->priority == DEFAULT_PRIO)
> +            pos->priority = DEFAULT_PRIO - 1;
>          pos = pos->next;
>      }
>  
> @@ -490,7 +494,10 @@ boot_prep(void)
>  
>      // Map drives and populate BEV list
>      struct bootentry_s *pos = BootList;
> -    while (pos) {
> +
> +    /* The priority of un-selected device is not changed,
> +       we only boot from user selected devices. */
> +    while (pos && pos->priority != DEFAULT_PRIO) {
>          switch (pos->type) {
>          case IPL_TYPE_BCV:
>              call_bcv(pos->vector.seg, pos->vector.offset);
> @@ -513,10 +520,6 @@ boot_prep(void)
>          }
>          pos = pos->next;
>      }
> -
> -    // If nothing added a floppy/hd boot - add it manually.
> -    add_bev(IPL_TYPE_FLOPPY, 0);
> -    add_bev(IPL_TYPE_HARDDISK, 0);
>  }
>  
>  
> -- 
> 1.7.1

--
			Gleb.
Kevin O'Connor - Dec. 19, 2012, 4:39 p.m.
On Wed, Dec 19, 2012 at 03:24:45PM +0800, Amos Kong wrote:
> Current seabios will try to boot from selected devices first,
> if they are all failed, seabios will also try to boot from
> un-selected devices.
> 
> For example:
> @ qemu-kvm -boot order=n,menu=on ...
> 
> Guest will boot from network first, if it's failed, guest will try to
> boot from other un-selected devices (floppy, cdrom, disk) one by one.
> 
> Sometimes, user don't want to boot from some devices. This patch changes
> seabios to boot only from selected devices.
> 
> If user choose first boot device from menu, then seabios will try all
> the devices, even some of them are not selected.

The BIOS Boot Specification (BBS) is quite complex and your patch
changes SeaBIOS' behavior in subtle ways that I'm not convinced is
safe.  (For example, by not always adding an FD/HD entry it may no
longer be possible to boot from a legacy option rom which emulates an
FD.)

Instead of altering the core algorithm for this feature, a different
approach would be to add a new "boot device" (eg, IPL_TYPE_HALT) that
is only registered if found in the bootorder file and just calls
boot_fail() when attempted.  That way users get the default behaviour
unless they explicitly request a halt in boot at a given priority.

-Kevin
Amos Kong - Dec. 25, 2012, 3:58 a.m.
On Wed, Dec 19, 2012 at 11:32:08AM +0200, Gleb Natapov wrote:
> On Wed, Dec 19, 2012 at 03:24:45PM +0800, Amos Kong wrote:
> > Current seabios will try to boot from selected devices first,
> > if they are all failed, seabios will also try to boot from
> > un-selected devices.
> > 
> > For example:
> > @ qemu-kvm -boot order=n,menu=on ...
> > 
> > Guest will boot from network first, if it's failed, guest will try to
> > boot from other un-selected devices (floppy, cdrom, disk) one by one.
> > 
> > Sometimes, user don't want to boot from some devices. This patch changes

Hi Gleb,

> And sometimes he want. The patch changes behaviour unconditionally. New
> behaviour should be user selectable. Something line -boot order=strict
> on qemu command line.

Sometimes, user don't know which devices are in boot list of seabios,
so they could not disable them through qemu cmdline.

I didn't describe the purpose clearly. Currently we can assign boot
order by "-boot order=...", if fails to boot from all devices in order
parameters, other devices in seabios's boot table will also be tried. 

The exact request should be "only boot from selected devices".

I agree to make it configurable.
eg:  qemu -boot order=nd,strict=on,menu=on
     strick: on  (only boot from selected devices)
     strick: off  (will try to boot from all devices in seabios' boot table)
     default strick should be 'off' as current behavior.
 
Thanks, Amos

> > seabios to boot only from selected devices.
> > 
> > If user choose first boot device from menu, then seabios will try all
> > the devices, even some of them are not selected.
> > 
> > Signed-off-by: Amos Kong <akong@redhat.com>
> > ---
> > Resend for CCing seabios maillist.
> > ---
> >  src/boot.c |   13 ++++++++-----
> >  1 files changed, 8 insertions(+), 5 deletions(-)
> > 
> > diff --git a/src/boot.c b/src/boot.c
> > index 3ca7960..ee810ac 100644
> > --- a/src/boot.c
> > +++ b/src/boot.c
> > @@ -424,6 +424,10 @@ interactive_bootmenu(void)
> >          maxmenu++;
> >          printf("%d. %s\n", maxmenu
> >                 , strtcpy(desc, pos->description, ARRAY_SIZE(desc)));
> > +        /* If user chooses first boot device from menu, we will treat
> > +	    all the devices as selected. */
> > +        if (pos->priority == DEFAULT_PRIO)
> > +            pos->priority = DEFAULT_PRIO - 1;
> >          pos = pos->next;
> >      }
> >  
> > @@ -490,7 +494,10 @@ boot_prep(void)
> >  
> >      // Map drives and populate BEV list
> >      struct bootentry_s *pos = BootList;
> > -    while (pos) {
> > +
> > +    /* The priority of un-selected device is not changed,
> > +       we only boot from user selected devices. */
> > +    while (pos && pos->priority != DEFAULT_PRIO) {
> >          switch (pos->type) {
> >          case IPL_TYPE_BCV:
> >              call_bcv(pos->vector.seg, pos->vector.offset);
> > @@ -513,10 +520,6 @@ boot_prep(void)
> >          }
> >          pos = pos->next;
> >      }
> > -
> > -    // If nothing added a floppy/hd boot - add it manually.
> > -    add_bev(IPL_TYPE_FLOPPY, 0);
> > -    add_bev(IPL_TYPE_HARDDISK, 0);
Gleb Natapov - Dec. 25, 2012, 6:37 a.m.
On Tue, Dec 25, 2012 at 11:58:08AM +0800, Amos Kong wrote:
> On Wed, Dec 19, 2012 at 11:32:08AM +0200, Gleb Natapov wrote:
> > On Wed, Dec 19, 2012 at 03:24:45PM +0800, Amos Kong wrote:
> > > Current seabios will try to boot from selected devices first,
> > > if they are all failed, seabios will also try to boot from
> > > un-selected devices.
> > > 
> > > For example:
> > > @ qemu-kvm -boot order=n,menu=on ...
> > > 
> > > Guest will boot from network first, if it's failed, guest will try to
> > > boot from other un-selected devices (floppy, cdrom, disk) one by one.
> > > 
> > > Sometimes, user don't want to boot from some devices. This patch changes
> 
> Hi Gleb,
> 
> > And sometimes he want. The patch changes behaviour unconditionally. New
> > behaviour should be user selectable. Something line -boot order=strict
> > on qemu command line.
> 
> Sometimes, user don't know which devices are in boot list of seabios,
> so they could not disable them through qemu cmdline.
> 
This is not what I suggested though. And currently we do not have a way
to remove one device from the boot process. This is separate issue and
requires separate patch.

> I didn't describe the purpose clearly. Currently we can assign boot
> order by "-boot order=...", if fails to boot from all devices in order
> parameters, other devices in seabios's boot table will also be tried. 
order= is an old style. Use bootindex instead.

> 
> The exact request should be "only boot from selected devices".
You described the purpose clearly first time. This is how I understood
it :)

> 
> I agree to make it configurable.
> eg:  qemu -boot order=nd,strict=on,menu=on
>      strick: on  (only boot from selected devices)
>      strick: off  (will try to boot from all devices in seabios' boot table)
>      default strick should be 'off' as current behavior.
>  
Yes, this is my suggestion.

> Thanks, Amos
> 
> > > seabios to boot only from selected devices.
> > > 
> > > If user choose first boot device from menu, then seabios will try all
> > > the devices, even some of them are not selected.
> > > 
> > > Signed-off-by: Amos Kong <akong@redhat.com>
> > > ---
> > > Resend for CCing seabios maillist.
> > > ---
> > >  src/boot.c |   13 ++++++++-----
> > >  1 files changed, 8 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/src/boot.c b/src/boot.c
> > > index 3ca7960..ee810ac 100644
> > > --- a/src/boot.c
> > > +++ b/src/boot.c
> > > @@ -424,6 +424,10 @@ interactive_bootmenu(void)
> > >          maxmenu++;
> > >          printf("%d. %s\n", maxmenu
> > >                 , strtcpy(desc, pos->description, ARRAY_SIZE(desc)));
> > > +        /* If user chooses first boot device from menu, we will treat
> > > +	    all the devices as selected. */
> > > +        if (pos->priority == DEFAULT_PRIO)
> > > +            pos->priority = DEFAULT_PRIO - 1;
> > >          pos = pos->next;
> > >      }
> > >  
> > > @@ -490,7 +494,10 @@ boot_prep(void)
> > >  
> > >      // Map drives and populate BEV list
> > >      struct bootentry_s *pos = BootList;
> > > -    while (pos) {
> > > +
> > > +    /* The priority of un-selected device is not changed,
> > > +       we only boot from user selected devices. */
> > > +    while (pos && pos->priority != DEFAULT_PRIO) {
> > >          switch (pos->type) {
> > >          case IPL_TYPE_BCV:
> > >              call_bcv(pos->vector.seg, pos->vector.offset);
> > > @@ -513,10 +520,6 @@ boot_prep(void)
> > >          }
> > >          pos = pos->next;
> > >      }
> > > -
> > > -    // If nothing added a floppy/hd boot - add it manually.
> > > -    add_bev(IPL_TYPE_FLOPPY, 0);
> > > -    add_bev(IPL_TYPE_HARDDISK, 0);

--
			Gleb.
Amos Kong - Dec. 25, 2012, 10:37 a.m.
On Tue, Dec 25, 2012 at 08:37:07AM +0200, Gleb Natapov wrote:
> On Tue, Dec 25, 2012 at 11:58:08AM +0800, Amos Kong wrote:
> > On Wed, Dec 19, 2012 at 11:32:08AM +0200, Gleb Natapov wrote:
> > > On Wed, Dec 19, 2012 at 03:24:45PM +0800, Amos Kong wrote:
> > > > Current seabios will try to boot from selected devices first,
> > > > if they are all failed, seabios will also try to boot from
> > > > un-selected devices.
> > > > 
> > > > For example:
> > > > @ qemu-kvm -boot order=n,menu=on ...
> > > > 
> > > > Guest will boot from network first, if it's failed, guest will try to
> > > > boot from other un-selected devices (floppy, cdrom, disk) one by one.
> > > > 
> > > > Sometimes, user don't want to boot from some devices. This patch changes
> > 
> > Hi Gleb,
> > 
> > > And sometimes he want. The patch changes behaviour unconditionally. New
> > > behaviour should be user selectable. Something line -boot order=strict
> > > on qemu command line.
> > 
> > Sometimes, user don't know which devices are in boot list of seabios,
> > so they could not disable them through qemu cmdline.

Hi Gleb, Kevin

> This is not what I suggested though. And currently we do not have a way
> to remove one device from the boot process. This is separate issue and
> requires separate patch.

issue 1: add a qemu parameter to tell seabios don't boot from unselected device
issue 2: add the ability to seabios to ignore unselected device

right?
 
> > I didn't describe the purpose clearly. Currently we can assign boot
> > order by "-boot order=...", if fails to boot from all devices in order
> > parameters, other devices in seabios's boot table will also be tried. 
> order= is an old style. Use bootindex instead.
 

(I'm trying to describe the old/new principles, correct me if sth is
wrong, thanks)

+ Old style: order=...

There are two registers in Bochs/qemu's CMOS map, which are used for
boot sequence.
(number of boot devices <= 3)
-------------------------------------------------------
0x38 S    eltorito boot sequence + boot signature check
     bits
     0    floppy boot signature check (1: disabled, 0: enabled)
     7-4  boot drive #3 (0: unused, 1: fd, 2: hd, 3:cd, else: fd)

0x3d S    eltorito boot sequence (see above)
     bits
     3-0  boot drive #1
     7-4  boot drive #2

==> set order in qemu:
hw/pc.c: set_boot_dev(ISADevice *s, const char *boot_device, ..) {
    ...
    rtc_set_memory(s, 0x3d, (bds[1] << 4) | bds[0]);
    rtc_set_memory(s, 0x38, (bds[2] << 4) | (fd_bootchk ? 0x0 : 0x1));
}

==> process order in seabios:
seabios/src/boot.c: boot_setup():
        u32 bootorder = (inb_cmos(CMOS_BIOS_BOOTFLAG2)
              | ((inb_cmos(CMOS_BIOS_BOOTFLAG1) & 0xf0) << 4));
        DefaultFloppyPrio = DefaultCDPrio = DefaultHDPrio
            = DefaultBEVPrio = DEFAULT_PRIO;

^^^ device priority will be set to 9999 before processing
        int i;
        for (i=101; i<104; i++) {
            u32 val = bootorder & 0x0f;
            bootorder >>= 4;
            switch (val) {
            case 1: DefaultFloppyPrio = i; break;
            case 2: DefaultHDPrio = i;     break;
            case 3: DefaultCDPrio = i;     break;
            case 4: DefaultBEVPrio = i;    break;

^^^ if one device is selected in cmos register, its priority will be
set to 10*, the priority of un-selected devices are still 9999.
            }
        }


+ New style: bootindex
  a bootorder string which contains the descriptions of boot devices.
  (eg. /pci@i0cf8/ethernet@3/ethernet-phy@0\n...)
  it's loaded through 'bootorder' file in rom by seabios.
  So 'selected' device can be found in this string.
  seabios will use the table index as the priority of selected devices.

  Seabios uses boot_add_{floppy,floppy,hd,bcv,cd,cbfs} to add devices
  to boot entry list. the priority will be processed at this point by:
    defPrio(prio, Default...Prio)

  'prio' is got when init the device, two conditions:
      -1: unselected
      index of bootorder table: selected in bootorder rom file.

  So after processing, priority of unselected devices will be re-set to 9999.

Based on this, we can judge if device is selected or not by checking
if priority is 9999. The only problem should be legacy FD/HD.

However, it's better to add a flag ('selected') in struct bev_s. If
qemu tells seabios to ignore unselected devices, we can ignore them in
do_boot().

// Determine next boot method and attempt a boot using it.
static void do_boot(int seq_nr) {
    ....
    // Boot the given BEV type. 
    struct bev_s *ie = &BEV[seq_nr];
    if (!ie->selected)
        boot_fail();
    ...

> > The exact request should be "only boot from selected devices".
> You described the purpose clearly first time. This is how I understood
> it :)
> 
> > 
> > I agree to make it configurable.
> > eg:  qemu -boot order=nd,strict=on,menu=on
> >      strick: on  (only boot from selected devices)
> >      strick: off  (will try to boot from all devices in seabios' boot table)
> >      default strick should be 'off' as current behavior.
> >  
> Yes, this is my suggestion.
> 
> > Thanks, Amos
> > 
> > > > seabios to boot only from selected devices.
> > > > 
> > > > If user choose first boot device from menu, then seabios will try all
> > > > the devices, even some of them are not selected.
> > >

Hi Kevin,

> > > The BIOS Boot Specification (BBS) is quite complex and your patch
> > > changes SeaBIOS' behavior in subtle ways that I'm not convinced is
> > > safe.  (For example, by not always adding an FD/HD entry it may no
> > > longer be possible to boot from a legacy option rom which emulates
> > > an
> > > FD.)

Yes, not easy as my solution.

> > > Instead of altering the core algorithm for this feature, a different
> > > approach would be to add a new "boot device" (eg, IPL_TYPE_HALT)
> > > that
> > > is only registered if found in the bootorder file and just calls
> > > boot_fail() when attempted.

But how to know if device is seleted or not? Bios processes the
bootorder complexly. But I find the priority is a clew.

Thanks, Amos

>   That way users get the default
> > > behaviour
> > > unless they explicitly request a halt in boot at a given priority.
> > > 
> > > -Kevin

> > > > Signed-off-by: Amos Kong <akong@redhat.com>
> > > > ---
> > > > Resend for CCing seabios maillist.
> > > > ---
> > > >  src/boot.c |   13 ++++++++-----
> > > >  1 files changed, 8 insertions(+), 5 deletions(-)
> > > > 
> > > > diff --git a/src/boot.c b/src/boot.c
> > > > index 3ca7960..ee810ac 100644
> > > > --- a/src/boot.c
> > > > +++ b/src/boot.c
> > > > @@ -424,6 +424,10 @@ interactive_bootmenu(void)
> > > >          maxmenu++;
> > > >          printf("%d. %s\n", maxmenu
> > > >                 , strtcpy(desc, pos->description, ARRAY_SIZE(desc)));
> > > > +        /* If user chooses first boot device from menu, we will treat
> > > > +	    all the devices as selected. */
> > > > +        if (pos->priority == DEFAULT_PRIO)
> > > > +            pos->priority = DEFAULT_PRIO - 1;
> > > >          pos = pos->next;
> > > >      }
> > > >  
> > > > @@ -490,7 +494,10 @@ boot_prep(void)
> > > >  
> > > >      // Map drives and populate BEV list
> > > >      struct bootentry_s *pos = BootList;
> > > > -    while (pos) {
> > > > +
> > > > +    /* The priority of un-selected device is not changed,
> > > > +       we only boot from user selected devices. */
> > > > +    while (pos && pos->priority != DEFAULT_PRIO) {
> > > >          switch (pos->type) {
> > > >          case IPL_TYPE_BCV:
> > > >              call_bcv(pos->vector.seg, pos->vector.offset);
> > > > @@ -513,10 +520,6 @@ boot_prep(void)
> > > >          }
> > > >          pos = pos->next;
> > > >      }
> > > > -
> > > > -    // If nothing added a floppy/hd boot - add it manually.
> > > > -    add_bev(IPL_TYPE_FLOPPY, 0);
> > > > -    add_bev(IPL_TYPE_HARDDISK, 0);
Ronen Hod - Dec. 25, 2012, 3:59 p.m.
On 12/19/2012 11:32 AM, Gleb Natapov wrote:
> On Wed, Dec 19, 2012 at 03:24:45PM +0800, Amos Kong wrote:
>> Current seabios will try to boot from selected devices first,
>> if they are all failed, seabios will also try to boot from
>> un-selected devices.
>>
>> For example:
>> @ qemu-kvm -boot order=n,menu=on ...
>>
>> Guest will boot from network first, if it's failed, guest will try to
>> boot from other un-selected devices (floppy, cdrom, disk) one by one.
>>
>> Sometimes, user don't want to boot from some devices. This patch changes
> And sometimes he want. The patch changes behaviour unconditionally. New
> behaviour should be user selectable. Something line -boot order=strict
> on qemu command line.

Another option would be to add a "terminator" symbol, say "T" (I couldn't find a good terminator), so that order=ndT, would mean strict "nd".

Ronen.

>
>> seabios to boot only from selected devices.
>>
>> If user choose first boot device from menu, then seabios will try all
>> the devices, even some of them are not selected.
>>
>> Signed-off-by: Amos Kong <akong@redhat.com>
>> ---
>> Resend for CCing seabios maillist.
>> ---
>>   src/boot.c |   13 ++++++++-----
>>   1 files changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/src/boot.c b/src/boot.c
>> index 3ca7960..ee810ac 100644
>> --- a/src/boot.c
>> +++ b/src/boot.c
>> @@ -424,6 +424,10 @@ interactive_bootmenu(void)
>>           maxmenu++;
>>           printf("%d. %s\n", maxmenu
>>                  , strtcpy(desc, pos->description, ARRAY_SIZE(desc)));
>> +        /* If user chooses first boot device from menu, we will treat
>> +	    all the devices as selected. */
>> +        if (pos->priority == DEFAULT_PRIO)
>> +            pos->priority = DEFAULT_PRIO - 1;
>>           pos = pos->next;
>>       }
>>   
>> @@ -490,7 +494,10 @@ boot_prep(void)
>>   
>>       // Map drives and populate BEV list
>>       struct bootentry_s *pos = BootList;
>> -    while (pos) {
>> +
>> +    /* The priority of un-selected device is not changed,
>> +       we only boot from user selected devices. */
>> +    while (pos && pos->priority != DEFAULT_PRIO) {
>>           switch (pos->type) {
>>           case IPL_TYPE_BCV:
>>               call_bcv(pos->vector.seg, pos->vector.offset);
>> @@ -513,10 +520,6 @@ boot_prep(void)
>>           }
>>           pos = pos->next;
>>       }
>> -
>> -    // If nothing added a floppy/hd boot - add it manually.
>> -    add_bev(IPL_TYPE_FLOPPY, 0);
>> -    add_bev(IPL_TYPE_HARDDISK, 0);
>>   }
>>   
>>   
>> -- 
>> 1.7.1
> --
> 			Gleb.
>
Gleb Natapov - Dec. 25, 2012, 5:15 p.m.
On Tue, Dec 25, 2012 at 05:59:04PM +0200, Ronen Hod wrote:
> On 12/19/2012 11:32 AM, Gleb Natapov wrote:
> >On Wed, Dec 19, 2012 at 03:24:45PM +0800, Amos Kong wrote:
> >>Current seabios will try to boot from selected devices first,
> >>if they are all failed, seabios will also try to boot from
> >>un-selected devices.
> >>
> >>For example:
> >>@ qemu-kvm -boot order=n,menu=on ...
> >>
> >>Guest will boot from network first, if it's failed, guest will try to
> >>boot from other un-selected devices (floppy, cdrom, disk) one by one.
> >>
> >>Sometimes, user don't want to boot from some devices. This patch changes
> >And sometimes he want. The patch changes behaviour unconditionally. New
> >behaviour should be user selectable. Something line -boot order=strict
> >on qemu command line.
> 
> Another option would be to add a "terminator" symbol, say "T" (I couldn't find a good terminator), so that order=ndT, would mean strict "nd".
> 
Not very helpful if the order is specified with bootindex like it
should.

> Ronen.
> 
> >
> >>seabios to boot only from selected devices.
> >>
> >>If user choose first boot device from menu, then seabios will try all
> >>the devices, even some of them are not selected.
> >>
> >>Signed-off-by: Amos Kong <akong@redhat.com>
> >>---
> >>Resend for CCing seabios maillist.
> >>---
> >>  src/boot.c |   13 ++++++++-----
> >>  1 files changed, 8 insertions(+), 5 deletions(-)
> >>
> >>diff --git a/src/boot.c b/src/boot.c
> >>index 3ca7960..ee810ac 100644
> >>--- a/src/boot.c
> >>+++ b/src/boot.c
> >>@@ -424,6 +424,10 @@ interactive_bootmenu(void)
> >>          maxmenu++;
> >>          printf("%d. %s\n", maxmenu
> >>                 , strtcpy(desc, pos->description, ARRAY_SIZE(desc)));
> >>+        /* If user chooses first boot device from menu, we will treat
> >>+	    all the devices as selected. */
> >>+        if (pos->priority == DEFAULT_PRIO)
> >>+            pos->priority = DEFAULT_PRIO - 1;
> >>          pos = pos->next;
> >>      }
> >>@@ -490,7 +494,10 @@ boot_prep(void)
> >>      // Map drives and populate BEV list
> >>      struct bootentry_s *pos = BootList;
> >>-    while (pos) {
> >>+
> >>+    /* The priority of un-selected device is not changed,
> >>+       we only boot from user selected devices. */
> >>+    while (pos && pos->priority != DEFAULT_PRIO) {
> >>          switch (pos->type) {
> >>          case IPL_TYPE_BCV:
> >>              call_bcv(pos->vector.seg, pos->vector.offset);
> >>@@ -513,10 +520,6 @@ boot_prep(void)
> >>          }
> >>          pos = pos->next;
> >>      }
> >>-
> >>-    // If nothing added a floppy/hd boot - add it manually.
> >>-    add_bev(IPL_TYPE_FLOPPY, 0);
> >>-    add_bev(IPL_TYPE_HARDDISK, 0);
> >>  }
> >>-- 
> >>1.7.1
> >--
> >			Gleb.
> >

--
			Gleb.

Patch

diff --git a/src/boot.c b/src/boot.c
index 3ca7960..ee810ac 100644
--- a/src/boot.c
+++ b/src/boot.c
@@ -424,6 +424,10 @@  interactive_bootmenu(void)
         maxmenu++;
         printf("%d. %s\n", maxmenu
                , strtcpy(desc, pos->description, ARRAY_SIZE(desc)));
+        /* If user chooses first boot device from menu, we will treat
+	    all the devices as selected. */
+        if (pos->priority == DEFAULT_PRIO)
+            pos->priority = DEFAULT_PRIO - 1;
         pos = pos->next;
     }
 
@@ -490,7 +494,10 @@  boot_prep(void)
 
     // Map drives and populate BEV list
     struct bootentry_s *pos = BootList;
-    while (pos) {
+
+    /* The priority of un-selected device is not changed,
+       we only boot from user selected devices. */
+    while (pos && pos->priority != DEFAULT_PRIO) {
         switch (pos->type) {
         case IPL_TYPE_BCV:
             call_bcv(pos->vector.seg, pos->vector.offset);
@@ -513,10 +520,6 @@  boot_prep(void)
         }
         pos = pos->next;
     }
-
-    // If nothing added a floppy/hd boot - add it manually.
-    add_bev(IPL_TYPE_FLOPPY, 0);
-    add_bev(IPL_TYPE_HARDDISK, 0);
 }