| Message ID | 20240322164139.678228-1-cassel@kernel.org |
|---|---|
| State | New |
| Headers | show |
| Series | [v4] misc: pci_endpoint_test: Use memcpy_toio()/memcpy_fromio() for BAR tests | expand |
On 3/22/24 9:41 AM, Niklas Cassel wrote: > The current code uses writel()/readl(), which has an implicit memory > barrier for every single readl()/writel(). > > Additionally, reading 4 bytes at a time over the PCI bus is not really > optimal, considering that this code is running in an ioctl handler. > > Use memcpy_toio()/memcpy_fromio() for BAR tests. > > Before patch with a 4MB BAR: > $ time /usr/bin/pcitest -b 1 > BAR1: OKAY > real 0m 1.56s > > After patch with a 4MB BAR: > $ time /usr/bin/pcitest -b 1 > BAR1: OKAY > real 0m 0.54s > > Signed-off-by: Niklas Cassel <cassel@kernel.org> > --- > Changes since v3: > -Use scope-based resource management __free attribute from cleanup.h to > avoid overly verbose gotos and labels for error handling. > -Added a comment related to why we allocate a buffer of max 1MB. > (kmalloc() default upper limit is usually 4 MB on ARM and x86.) > > drivers/misc/pci_endpoint_test.c | 54 +++++++++++++++++++++++++------- > 1 file changed, 42 insertions(+), 12 deletions(-) > > diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c > index 705029ad8eb5..bf64d3aff7d8 100644 > --- a/drivers/misc/pci_endpoint_test.c > +++ b/drivers/misc/pci_endpoint_test.c > @@ -7,6 +7,7 @@ > */ > > #include <linux/crc32.h> > +#include <linux/cleanup.h> > #include <linux/delay.h> > #include <linux/fs.h> > #include <linux/io.h> > @@ -272,31 +273,60 @@ static const u32 bar_test_pattern[] = { > 0xA5A5A5A5, > }; > > +static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test, > + enum pci_barno barno, int offset, > + void *write_buf, void *read_buf, > + int size) > +{ > + memset(write_buf, bar_test_pattern[barno], size); > + memcpy_toio(test->bar[barno] + offset, write_buf, size); > + > + memcpy_fromio(read_buf, test->bar[barno] + offset, size); > + > + return memcmp(write_buf, read_buf, size); > +} > + > static bool pci_endpoint_test_bar(struct pci_endpoint_test *test, > enum pci_barno barno) > { > - int j; > - u32 val; > - int size; > + int j, bar_size, buf_size, iters, remain; > + void *write_buf __free(kfree) = NULL; > + void *read_buf __free(kfree) = NULL; Please check the following cleanup doc. Recommendation is to avoid above __free(kfree) = NULL declarations and directly define write_buf/read_buf. https://lore.kernel.org/lkml/171097196970.1011049.9726486429680041876.stgit@dwillia2-xfh.jf.intel.com/T/#m05d71a668ff0fad46c2055dbdcde55d7381780b7 > struct pci_dev *pdev = test->pdev; > > if (!test->bar[barno]) > return false; > > - size = pci_resource_len(pdev, barno); > + bar_size = pci_resource_len(pdev, barno); > > if (barno == test->test_reg_bar) > - size = 0x4; > + bar_size = 0x4; > > - for (j = 0; j < size; j += 4) > - pci_endpoint_test_bar_writel(test, barno, j, > - bar_test_pattern[barno]); > + /* > + * Allocate a buffer of max size 1MB, and reuse that buffer while > + * iterating over the whole BAR size (which might be much larger). > + */ > + buf_size = min(SZ_1M, bar_size); > > - for (j = 0; j < size; j += 4) { > - val = pci_endpoint_test_bar_readl(test, barno, j); > - if (val != bar_test_pattern[barno]) > + write_buf = kmalloc(buf_size, GFP_KERNEL); > + if (!write_buf) > + return false; > + > + read_buf = kmalloc(buf_size, GFP_KERNEL); > + if (!read_buf) > + return false; > + > + iters = bar_size / buf_size; > + for (j = 0; j < iters; j++) > + if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j, > + write_buf, read_buf, buf_size)) > + return false; > + > + remain = bar_size % buf_size; > + if (remain) > + if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * iters, > + write_buf, read_buf, remain)) > return false; > - } > > return true; > }
Hello Kuppuswamy, Dan, On Fri, Mar 22, 2024 at 10:03:12AM -0700, Kuppuswamy Sathyanarayanan wrote: > > + > > static bool pci_endpoint_test_bar(struct pci_endpoint_test *test, > > enum pci_barno barno) > > { > > - int j; > > - u32 val; > > - int size; > > + int j, bar_size, buf_size, iters, remain; > > + void *write_buf __free(kfree) = NULL; > > + void *read_buf __free(kfree) = NULL; > > Please check the following cleanup doc. Recommendation is to avoid above __free(kfree) = NULL declarations and directly define write_buf/read_buf. > > https://lore.kernel.org/lkml/171097196970.1011049.9726486429680041876.stgit@dwillia2-xfh.jf.intel.com/T/#m05d71a668ff0fad46c2055dbdcde55d7381780b7 I don't think that the docs say that using: void *ptr __free(kfree) = NULL; is always an anti-pattern. "If other cleanup helpers appeared in such a function that depended on @dev being live to complete their unwind then using the "struct obj_type *obj __free(...) = NULL" style is an anti-pattern that potentially causes a use-after-free bug." I think it says that it is an anti-pattern IFF there are two cleanup helpers in a function AND they have have a inter-dependency. This patch just adds a single cleanup helper, so there can be no inter-dependency problem. This pattern is common in Linus's current tree, see e.g. $ git grep -C 3 -E "__free(.*) = NULL" If this was a problem, I don't think we would have seen 100 different instances of this pattern. In other words, I think this patch is fine. Dan, please correct me if I'm wrong. Kind regards, Niklas
On Fri, Mar 22, 2024 at 05:41:38PM +0100, Niklas Cassel wrote: > The current code uses writel()/readl(), which has an implicit memory > barrier for every single readl()/writel(). > > Additionally, reading 4 bytes at a time over the PCI bus is not really > optimal, considering that this code is running in an ioctl handler. > > Use memcpy_toio()/memcpy_fromio() for BAR tests. > > Before patch with a 4MB BAR: > $ time /usr/bin/pcitest -b 1 > BAR1: OKAY > real 0m 1.56s > > After patch with a 4MB BAR: > $ time /usr/bin/pcitest -b 1 > BAR1: OKAY > real 0m 0.54s > > Signed-off-by: Niklas Cassel <cassel@kernel.org> > --- > Changes since v3: > -Use scope-based resource management __free attribute from cleanup.h to > avoid overly verbose gotos and labels for error handling. > -Added a comment related to why we allocate a buffer of max 1MB. > (kmalloc() default upper limit is usually 4 MB on ARM and x86.) > > drivers/misc/pci_endpoint_test.c | 54 +++++++++++++++++++++++++------- > 1 file changed, 42 insertions(+), 12 deletions(-) > > diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c > index 705029ad8eb5..bf64d3aff7d8 100644 > --- a/drivers/misc/pci_endpoint_test.c > +++ b/drivers/misc/pci_endpoint_test.c > @@ -7,6 +7,7 @@ > */ > > #include <linux/crc32.h> > +#include <linux/cleanup.h> > #include <linux/delay.h> > #include <linux/fs.h> > #include <linux/io.h> > @@ -272,31 +273,60 @@ static const u32 bar_test_pattern[] = { > 0xA5A5A5A5, > }; > > +static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test, > + enum pci_barno barno, int offset, > + void *write_buf, void *read_buf, > + int size) > +{ > + memset(write_buf, bar_test_pattern[barno], size); > + memcpy_toio(test->bar[barno] + offset, write_buf, size); > + > + memcpy_fromio(read_buf, test->bar[barno] + offset, size); > + > + return memcmp(write_buf, read_buf, size); > +} > + > static bool pci_endpoint_test_bar(struct pci_endpoint_test *test, > enum pci_barno barno) > { > - int j; > - u32 val; > - int size; > + int j, bar_size, buf_size, iters, remain; > + void *write_buf __free(kfree) = NULL; > + void *read_buf __free(kfree) = NULL; > struct pci_dev *pdev = test->pdev; > > if (!test->bar[barno]) > return false; > > - size = pci_resource_len(pdev, barno); > + bar_size = pci_resource_len(pdev, barno); > > if (barno == test->test_reg_bar) > - size = 0x4; > + bar_size = 0x4; > > - for (j = 0; j < size; j += 4) > - pci_endpoint_test_bar_writel(test, barno, j, > - bar_test_pattern[barno]); > + /* > + * Allocate a buffer of max size 1MB, and reuse that buffer while > + * iterating over the whole BAR size (which might be much larger). > + */ > + buf_size = min(SZ_1M, bar_size); > > - for (j = 0; j < size; j += 4) { > - val = pci_endpoint_test_bar_readl(test, barno, j); > - if (val != bar_test_pattern[barno]) > + write_buf = kmalloc(buf_size, GFP_KERNEL); > + if (!write_buf) > + return false; > + > + read_buf = kmalloc(buf_size, GFP_KERNEL); > + if (!read_buf) > + return false; > + > + iters = bar_size / buf_size; > + for (j = 0; j < iters; j++) > + if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j, > + write_buf, read_buf, buf_size)) > + return false; > + > + remain = bar_size % buf_size; > + if (remain) > + if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * iters, > + write_buf, read_buf, remain)) > return false; > - } > > return true; > } > -- > 2.44.0 > Gentle ping :) Kind regards, Niklas
On 3/22/24 9:41 AM, Niklas Cassel wrote: > The current code uses writel()/readl(), which has an implicit memory > barrier for every single readl()/writel(). > > Additionally, reading 4 bytes at a time over the PCI bus is not really > optimal, considering that this code is running in an ioctl handler. > > Use memcpy_toio()/memcpy_fromio() for BAR tests. > > Before patch with a 4MB BAR: > $ time /usr/bin/pcitest -b 1 > BAR1: OKAY > real 0m 1.56s > > After patch with a 4MB BAR: > $ time /usr/bin/pcitest -b 1 > BAR1: OKAY > real 0m 0.54s > > Signed-off-by: Niklas Cassel <cassel@kernel.org> > --- LGTM Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> > Changes since v3: > -Use scope-based resource management __free attribute from cleanup.h to > avoid overly verbose gotos and labels for error handling. > -Added a comment related to why we allocate a buffer of max 1MB. > (kmalloc() default upper limit is usually 4 MB on ARM and x86.) > > drivers/misc/pci_endpoint_test.c | 54 +++++++++++++++++++++++++------- > 1 file changed, 42 insertions(+), 12 deletions(-) > > diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c > index 705029ad8eb5..bf64d3aff7d8 100644 > --- a/drivers/misc/pci_endpoint_test.c > +++ b/drivers/misc/pci_endpoint_test.c > @@ -7,6 +7,7 @@ > */ > > #include <linux/crc32.h> > +#include <linux/cleanup.h> > #include <linux/delay.h> > #include <linux/fs.h> > #include <linux/io.h> > @@ -272,31 +273,60 @@ static const u32 bar_test_pattern[] = { > 0xA5A5A5A5, > }; > > +static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test, > + enum pci_barno barno, int offset, > + void *write_buf, void *read_buf, > + int size) > +{ > + memset(write_buf, bar_test_pattern[barno], size); > + memcpy_toio(test->bar[barno] + offset, write_buf, size); > + > + memcpy_fromio(read_buf, test->bar[barno] + offset, size); > + > + return memcmp(write_buf, read_buf, size); > +} > + > static bool pci_endpoint_test_bar(struct pci_endpoint_test *test, > enum pci_barno barno) > { > - int j; > - u32 val; > - int size; > + int j, bar_size, buf_size, iters, remain; > + void *write_buf __free(kfree) = NULL; > + void *read_buf __free(kfree) = NULL; > struct pci_dev *pdev = test->pdev; > > if (!test->bar[barno]) > return false; > > - size = pci_resource_len(pdev, barno); > + bar_size = pci_resource_len(pdev, barno); > > if (barno == test->test_reg_bar) > - size = 0x4; > + bar_size = 0x4; > > - for (j = 0; j < size; j += 4) > - pci_endpoint_test_bar_writel(test, barno, j, > - bar_test_pattern[barno]); > + /* > + * Allocate a buffer of max size 1MB, and reuse that buffer while > + * iterating over the whole BAR size (which might be much larger). > + */ > + buf_size = min(SZ_1M, bar_size); > > - for (j = 0; j < size; j += 4) { > - val = pci_endpoint_test_bar_readl(test, barno, j); > - if (val != bar_test_pattern[barno]) > + write_buf = kmalloc(buf_size, GFP_KERNEL); > + if (!write_buf) > + return false; > + > + read_buf = kmalloc(buf_size, GFP_KERNEL); > + if (!read_buf) > + return false; > + > + iters = bar_size / buf_size; > + for (j = 0; j < iters; j++) > + if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j, > + write_buf, read_buf, buf_size)) > + return false; > + > + remain = bar_size % buf_size; > + if (remain) > + if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * iters, > + write_buf, read_buf, remain)) > return false; > - } > > return true; > }
diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c index 705029ad8eb5..bf64d3aff7d8 100644 --- a/drivers/misc/pci_endpoint_test.c +++ b/drivers/misc/pci_endpoint_test.c @@ -7,6 +7,7 @@ */ #include <linux/crc32.h> +#include <linux/cleanup.h> #include <linux/delay.h> #include <linux/fs.h> #include <linux/io.h> @@ -272,31 +273,60 @@ static const u32 bar_test_pattern[] = { 0xA5A5A5A5, }; +static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test, + enum pci_barno barno, int offset, + void *write_buf, void *read_buf, + int size) +{ + memset(write_buf, bar_test_pattern[barno], size); + memcpy_toio(test->bar[barno] + offset, write_buf, size); + + memcpy_fromio(read_buf, test->bar[barno] + offset, size); + + return memcmp(write_buf, read_buf, size); +} + static bool pci_endpoint_test_bar(struct pci_endpoint_test *test, enum pci_barno barno) { - int j; - u32 val; - int size; + int j, bar_size, buf_size, iters, remain; + void *write_buf __free(kfree) = NULL; + void *read_buf __free(kfree) = NULL; struct pci_dev *pdev = test->pdev; if (!test->bar[barno]) return false; - size = pci_resource_len(pdev, barno); + bar_size = pci_resource_len(pdev, barno); if (barno == test->test_reg_bar) - size = 0x4; + bar_size = 0x4; - for (j = 0; j < size; j += 4) - pci_endpoint_test_bar_writel(test, barno, j, - bar_test_pattern[barno]); + /* + * Allocate a buffer of max size 1MB, and reuse that buffer while + * iterating over the whole BAR size (which might be much larger). + */ + buf_size = min(SZ_1M, bar_size); - for (j = 0; j < size; j += 4) { - val = pci_endpoint_test_bar_readl(test, barno, j); - if (val != bar_test_pattern[barno]) + write_buf = kmalloc(buf_size, GFP_KERNEL); + if (!write_buf) + return false; + + read_buf = kmalloc(buf_size, GFP_KERNEL); + if (!read_buf) + return false; + + iters = bar_size / buf_size; + for (j = 0; j < iters; j++) + if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j, + write_buf, read_buf, buf_size)) + return false; + + remain = bar_size % buf_size; + if (remain) + if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * iters, + write_buf, read_buf, remain)) return false; - } return true; }
The current code uses writel()/readl(), which has an implicit memory barrier for every single readl()/writel(). Additionally, reading 4 bytes at a time over the PCI bus is not really optimal, considering that this code is running in an ioctl handler. Use memcpy_toio()/memcpy_fromio() for BAR tests. Before patch with a 4MB BAR: $ time /usr/bin/pcitest -b 1 BAR1: OKAY real 0m 1.56s After patch with a 4MB BAR: $ time /usr/bin/pcitest -b 1 BAR1: OKAY real 0m 0.54s Signed-off-by: Niklas Cassel <cassel@kernel.org> --- Changes since v3: -Use scope-based resource management __free attribute from cleanup.h to avoid overly verbose gotos and labels for error handling. -Added a comment related to why we allocate a buffer of max 1MB. (kmalloc() default upper limit is usually 4 MB on ARM and x86.) drivers/misc/pci_endpoint_test.c | 54 +++++++++++++++++++++++++------- 1 file changed, 42 insertions(+), 12 deletions(-)