MT76x2U crashes XHCI driver on AMD Ryzen system

MT76x2U crashes XHCI driver on AMD Ryzen system

[Stanislaw Gruszka]

On Sun, Mar 03, 2019@11:20:45PM -0800, Rosen Penev wrote:
> On Sun, Mar 3, 2019@11:10 PM Stanislaw Gruszka <sgruszka@redhat.com> wrote:
> >
> > On Thu, Feb 28, 2019@02:40:29PM +0100, Joerg Roedel wrote:
> > > On Thu, Feb 28, 2019@01:19:48PM +0100, Stanislaw Gruszka wrote:
> > > > Nevermind, the patch is wrong, s->dma_address is initalized in sg_num_pages().
> > >
> > > Yes, it is. In sg_num_pages() the offset into the IOMMU mapping is
> > > stored in s->dma_address, taking also the segment boundary mask into
> > > account. map_sg() later only adds the base-address to that.
> >
> > I have some more info about the issues in
> > https://bugzilla.kernel.org/show_bug.cgi?id=202673
> >
> > We have some bugs in mt76. Apparently we should not use
> > page_frag_alloc() with size bigger than PAGE_SIZE as page_frag_alloc()
> > can fallback to single page allocation. And also we should not make
> > sizes unaligned as pointed in commit:
> > 3bed3cc4156e ("net: Do not allocate page fragments that are not skb aligned"
> As a small and totally unrelated note, page_frag_alloc is only used in
> mt76 and the nvme driver ;)

And there is nvme problem on AMD IOMMU:
https://bugzilla.kernel.org/show_bug.cgi?id=202665

While page_frag_alloc() should be used with cautious, at least care of
size alignment with ARCH_DMA_MINALIGN (not for IOMMU, but standard arch
dma), at this point I think some of those issues are AMD IOMMU problems.

> > However after fixing that mt76usb still did not work. To make things
> > work we had to change rx frag size from 2048 to PAGE_SIZE and change
> > virt_to_head_page() to virt_to_page() when setting SG's.
>
> > I think I understand why first change was needed. If we do 2 separate
> > dma maps of 2 different buffers in single page i.e (PAGE + off=0
> > and PAGE + off=2048) it causes problem. So either map_sg() return
> > error which mt76usb does not handle correctly or there is issue
> > in AMD IOMMU because two dma maps use the same page.

Any comment on that? Is fine or not to do 2 or more dma mappings
within the same single page on AMD IOMMU? If not, is there any
mechanism for drivers to find out about this limitation to prevent
to prepare wrong SG buffers?

> > But I don't understand why the second change was needed. Without
> > it we have issue with incorrect page->_refcount . It is somehow
> > related with AMD IOMMU, because on different platforms we do not
> > have such problems.

I think I found a bug in amd iommu code when setting sg->dma_address
with sg->offset > PAGE_SIZE. Will post fix shortly. 

Stanislaw

[PATCH] iommu/amd: fix sg->dma_address for sg->offset bigger than PAGE_SIZE

[Stanislaw Gruszka]

Take into account that sg->offset can be bigger than PAGE_SIZE when
setting segment sg->dma_address. Otherwise sg->dma_address will point
at diffrent page, what makes DMA not possible with erros like this:

xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa70c0 flags=0x0020]
xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7040 flags=0x0020]
xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7080 flags=0x0020]
xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7100 flags=0x0020]
xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7000 flags=0x0020]

Additinally with wrong sg->dma_address unmap_sg will free wrong pages,
what what can cause crashes like this:

Feb 28 19:27:45 kernel: BUG: Bad page state in process cinnamon  pfn:39e8b1
Feb 28 19:27:45 kernel: Disabling lock debugging due to kernel taint
Feb 28 19:27:45 kernel: flags: 0x2ffff0000000000()
Feb 28 19:27:45 kernel: raw: 02ffff0000000000 0000000000000000 ffffffff00000301 0000000000000000
Feb 28 19:27:45 kernel: raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
Feb 28 19:27:45 kernel: page dumped because: nonzero _refcount
Feb 28 19:27:45 kernel: Modules linked in: ccm fuse arc4 nct6775 hwmon_vid amdgpu nls_iso8859_1 nls_cp437 edac_mce_amd vfat fat kvm_amd ccp rng_core kvm mt76x0u mt76x0_common mt76x02_usb irqbypass mt76_usb mt76x02_lib mt76 crct10dif_pclmul crc32_pclmul chash mac80211 amd_iommu_v2 ghash_clmulni_intel gpu_sched i2c_algo_bit ttm wmi_bmof snd_hda_codec_realtek snd_hda_codec_generic drm_kms_helper snd_hda_codec_hdmi snd_hda_intel drm snd_hda_codec aesni_intel snd_hda_core snd_hwdep aes_x86_64 crypto_simd snd_pcm cfg80211 cryptd mousedev snd_timer glue_helper pcspkr r8169 input_leds realtek agpgart libphy rfkill snd syscopyarea sysfillrect sysimgblt fb_sys_fops soundcore sp5100_tco k10temp i2c_piix4 wmi evdev gpio_amdpt pinctrl_amd mac_hid pcc_cpufreq acpi_cpufreq sg ip_tables x_tables ext4(E) crc32c_generic(E) crc16(E) mbcache(E) jbd2(E) fscrypto(E) sd_mod(E) hid_generic(E) usbhid(E) hid(E) dm_mod(E) serio_raw(E) atkbd(E) libps2(E) crc32c_intel(E) ahci(E) libahci(E) libata(E) xhci_pci(E) xhci_hcd(E)
Feb 28 19:27:45 kernel:  scsi_mod(E) i8042(E) serio(E) bcache(E) crc64(E)
Feb 28 19:27:45 kernel: CPU: 2 PID: 896 Comm: cinnamon Tainted: G    B   W   E     4.20.12-arch1-1-custom #1
Feb 28 19:27:45 kernel: Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./B450M Pro4, BIOS P1.20 06/26/2018
Feb 28 19:27:45 kernel: Call Trace:
Feb 28 19:27:45 kernel:  dump_stack+0x5c/0x80
Feb 28 19:27:45 kernel:  bad_page.cold.29+0x7f/0xb2
Feb 28 19:27:45 kernel:  __free_pages_ok+0x2c0/0x2d0
Feb 28 19:27:45 kernel:  skb_release_data+0x96/0x180
Feb 28 19:27:45 kernel:  __kfree_skb+0xe/0x20
Feb 28 19:27:45 kernel:  tcp_recvmsg+0x894/0xc60
Feb 28 19:27:45 kernel:  ? reuse_swap_page+0x120/0x340
Feb 28 19:27:45 kernel:  ? ptep_set_access_flags+0x23/0x30
Feb 28 19:27:45 kernel:  inet_recvmsg+0x5b/0x100
Feb 28 19:27:45 kernel:  __sys_recvfrom+0xc3/0x180
Feb 28 19:27:45 kernel:  ? handle_mm_fault+0x10a/0x250
Feb 28 19:27:45 kernel:  ? syscall_trace_enter+0x1d3/0x2d0
Feb 28 19:27:45 kernel:  ? __audit_syscall_exit+0x22a/0x290
Feb 28 19:27:45 kernel:  __x64_sys_recvfrom+0x24/0x30
Feb 28 19:27:45 kernel:  do_syscall_64+0x5b/0x170
Feb 28 19:27:45 kernel:  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Cc: stable at vger.kernel.org
Reported-and-tested-by: jan.viktorin at gmail.com
Signed-off-by: Stanislaw Gruszka <sgruszka at redhat.com>
---
 drivers/iommu/amd_iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 6b0760dafb3e..949621f33624 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2604,7 +2604,7 @@ static int map_sg(struct device *dev, struct scatterlist *sglist,
 
 	/* Everything is mapped - write the right values into s->dma_address */
 	for_each_sg(sglist, s, nelems, i) {
-		s->dma_address += address + s->offset;
+		s->dma_address += address + (s->offset & ~PAGE_MASK);
 		s->dma_length   = s->length;
 	}
 
-- 
2.7.5

[PATCH] iommu/amd: fix sg->dma_address for sg->offset bigger than PAGE_SIZE

[Alexander Duyck]

On Mon, 2019-03-11@10:03 +0100, Stanislaw Gruszka wrote:
> Take into account that sg->offset can be bigger than PAGE_SIZE when
> setting segment sg->dma_address. Otherwise sg->dma_address will point
> at diffrent page, what makes DMA not possible with erros like this:
> 
> xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa70c0 flags=0x0020]
> xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7040 flags=0x0020]
> xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7080 flags=0x0020]
> xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7100 flags=0x0020]
> xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7000 flags=0x0020]
> 
> Additinally with wrong sg->dma_address unmap_sg will free wrong pages,
> what what can cause crashes like this:
> 
> Feb 28 19:27:45 kernel: BUG: Bad page state in process cinnamon  pfn:39e8b1
> Feb 28 19:27:45 kernel: Disabling lock debugging due to kernel taint
> Feb 28 19:27:45 kernel: flags: 0x2ffff0000000000()
> Feb 28 19:27:45 kernel: raw: 02ffff0000000000 0000000000000000 ffffffff00000301 0000000000000000
> Feb 28 19:27:45 kernel: raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
> Feb 28 19:27:45 kernel: page dumped because: nonzero _refcount
> Feb 28 19:27:45 kernel: Modules linked in: ccm fuse arc4 nct6775 hwmon_vid amdgpu nls_iso8859_1 nls_cp437 edac_mce_amd vfat fat kvm_amd ccp rng_core kvm mt76x0u mt76x0_common mt76x02_usb irqbypass mt76_usb mt76x02_lib mt76 crct10dif_pclmul crc32_pclmul chash mac80211 amd_iommu_v2 ghash_clmulni_intel gpu_sched i2c_algo_bit ttm wmi_bmof snd_hda_codec_realtek snd_hda_codec_generic drm_kms_helper snd_hda_codec_hdmi snd_hda_intel drm snd_hda_codec aesni_intel snd_hda_core snd_hwdep aes_x86_64 crypto_simd snd_pcm cfg80211 cryptd mousedev snd_timer glue_helper pcspkr r8169 input_leds realtek agpgart libphy rfkill snd syscopyarea sysfillrect sysimgblt fb_sys_fops soundcore sp5100_tco k10temp i2c_piix4 wmi evdev gpio_amdpt pinctrl_amd mac_hid pcc_cpufreq acpi_cpufreq sg ip_tables x_tables ext4(E) crc32c_generic(E) crc16(E) mbcache(E) jbd2(E) fscrypto(E) sd_mod(E) hid_generic(E) usbhid(E) hid(E) dm_mod(E) serio_raw(E) atkbd(E) libps2(E) crc32c_intel(E) ahci(E) libahci(E) libata(E) xhci_pci(E) xhci_hcd(E)
> Feb 28 19:27:45 kernel:  scsi_mod(E) i8042(E) serio(E) bcache(E) crc64(E)
> Feb 28 19:27:45 kernel: CPU: 2 PID: 896 Comm: cinnamon Tainted: G    B   W   E     4.20.12-arch1-1-custom #1
> Feb 28 19:27:45 kernel: Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./B450M Pro4, BIOS P1.20 06/26/2018
> Feb 28 19:27:45 kernel: Call Trace:
> Feb 28 19:27:45 kernel:  dump_stack+0x5c/0x80
> Feb 28 19:27:45 kernel:  bad_page.cold.29+0x7f/0xb2
> Feb 28 19:27:45 kernel:  __free_pages_ok+0x2c0/0x2d0
> Feb 28 19:27:45 kernel:  skb_release_data+0x96/0x180
> Feb 28 19:27:45 kernel:  __kfree_skb+0xe/0x20
> Feb 28 19:27:45 kernel:  tcp_recvmsg+0x894/0xc60
> Feb 28 19:27:45 kernel:  ? reuse_swap_page+0x120/0x340
> Feb 28 19:27:45 kernel:  ? ptep_set_access_flags+0x23/0x30
> Feb 28 19:27:45 kernel:  inet_recvmsg+0x5b/0x100
> Feb 28 19:27:45 kernel:  __sys_recvfrom+0xc3/0x180
> Feb 28 19:27:45 kernel:  ? handle_mm_fault+0x10a/0x250
> Feb 28 19:27:45 kernel:  ? syscall_trace_enter+0x1d3/0x2d0
> Feb 28 19:27:45 kernel:  ? __audit_syscall_exit+0x22a/0x290
> Feb 28 19:27:45 kernel:  __x64_sys_recvfrom+0x24/0x30
> Feb 28 19:27:45 kernel:  do_syscall_64+0x5b/0x170
> Feb 28 19:27:45 kernel:  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Cc: stable at vger.kernel.org
> Reported-and-tested-by: jan.viktorin at gmail.com
> Signed-off-by: Stanislaw Gruszka <sgruszka at redhat.com>
> ---
>  drivers/iommu/amd_iommu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index 6b0760dafb3e..949621f33624 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -2604,7 +2604,7 @@ static int map_sg(struct device *dev, struct scatterlist *sglist,
>  
>  	/* Everything is mapped - write the right values into s->dma_address */
>  	for_each_sg(sglist, s, nelems, i) {
> -		s->dma_address += address + s->offset;
> +		s->dma_address += address + (s->offset & ~PAGE_MASK);
>  		s->dma_length   = s->length;
>  	}
>  

You should add a comment calling out that this is needed because the
sg_phys(s) call above this is masked with PAGE_MASK. Then this makes
much more sense. Otherwise I would have assumed you needed either the
full offset or none.

Other than that, from that I can tell the code itself looks to be
correct, but just difficult to read.

Reviewed-by: Alexander Duyck <alexander.h.duyck at linux.intel.com>

[PATCH] iommu/amd: fix sg->dma_address for sg->offset bigger than PAGE_SIZE

[Stanislaw Gruszka]

On Mon, Mar 11, 2019@08:47:44AM -0700, Alexander Duyck wrote:
> >  drivers/iommu/amd_iommu.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> > index 6b0760dafb3e..949621f33624 100644
> > --- a/drivers/iommu/amd_iommu.c
> > +++ b/drivers/iommu/amd_iommu.c
> > @@ -2604,7 +2604,7 @@ static int map_sg(struct device *dev, struct scatterlist *sglist,
> >  
> >  	/* Everything is mapped - write the right values into s->dma_address */
> >  	for_each_sg(sglist, s, nelems, i) {
> > -		s->dma_address += address + s->offset;
> > +		s->dma_address += address + (s->offset & ~PAGE_MASK);
> >  		s->dma_length   = s->length;
> >  	}
> >  
> 
> You should add a comment calling out that this is needed because the
> sg_phys(s) call above this is masked with PAGE_MASK. Then this makes
> much more sense. Otherwise I would have assumed you needed either the
> full offset or none.

Would something like this 

/*
 * Everything is mapped - write the right values into s->dma_address. 
 * Take into account s->offset can be bigger than page size and sg_phys(s)
 * address has to be aligned to page granularity.
 */

be appropriate ?

Stanislaw

[PATCH] iommu/amd: fix sg->dma_address for sg->offset bigger than PAGE_SIZE

[Alexander Duyck]

On Tue, 2019-03-12@08:08 +0100, Stanislaw Gruszka wrote:
> On Mon, Mar 11, 2019@08:47:44AM -0700, Alexander Duyck wrote:
> > >  drivers/iommu/amd_iommu.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> > > index 6b0760dafb3e..949621f33624 100644
> > > --- a/drivers/iommu/amd_iommu.c
> > > +++ b/drivers/iommu/amd_iommu.c
> > > @@ -2604,7 +2604,7 @@ static int map_sg(struct device *dev, struct scatterlist *sglist,
> > >  
> > >  	/* Everything is mapped - write the right values into s->dma_address */
> > >  	for_each_sg(sglist, s, nelems, i) {
> > > -		s->dma_address += address + s->offset;
> > > +		s->dma_address += address + (s->offset & ~PAGE_MASK);
> > >  		s->dma_length   = s->length;
> > >  	}
> > >  
> > 
> > You should add a comment calling out that this is needed because the
> > sg_phys(s) call above this is masked with PAGE_MASK. Then this makes
> > much more sense. Otherwise I would have assumed you needed either the
> > full offset or none.
> 
> Would something like this 
> 
> /*
>  * Everything is mapped - write the right values into s->dma_address. 
>  * Take into account s->offset can be bigger than page size and sg_phys(s)
>  * address has to be aligned to page granularity.
>  */
> 
> be appropriate ?
> 
> Stanislaw
> 

No, that isn't a good description. If you take a look at the code a few
lines up you find:
	phys_addr = (sg_phys(s) & PAGE_MASK) + (j << PAGE_SHIFT);

Now if I am not mistaken the whole reason why you are having to make
the change here is because the application of PAGE_MASK in this line.
Basically what sg_phys() will do is take the address of the page,
convert it to a physical address and add the offset. However what the
mask is doing is limiting how much of that offset can be added. As a
result you have to add the remainder that was masked out. So maybe a
better comment would be something like:

/*
 * Add in the remaining piece of the scatter-gather offset that was 
 * masked out when we were determining the physical address via
 * (sg_phys(s) & PAGE_MASK) earlier.
 */

[PATCH v2] iommu/amd: fix sg->dma_address for sg->offset bigger than PAGE_SIZE

[Stanislaw Gruszka]

Take into account that sg->offset can be bigger than PAGE_SIZE when
setting segment sg->dma_address. Otherwise sg->dma_address will point
at diffrent page, what makes DMA not possible with erros like this:

xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa70c0 flags=0x0020]
xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7040 flags=0x0020]
xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7080 flags=0x0020]
xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7100 flags=0x0020]
xhci_hcd 0000:38:00.3: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000 address=0x00000000fdaa7000 flags=0x0020]

Additinally with wrong sg->dma_address unmap_sg will free wrong pages,
what what can cause crashes like this:

Feb 28 19:27:45 kernel: BUG: Bad page state in process cinnamon  pfn:39e8b1
Feb 28 19:27:45 kernel: Disabling lock debugging due to kernel taint
Feb 28 19:27:45 kernel: flags: 0x2ffff0000000000()
Feb 28 19:27:45 kernel: raw: 02ffff0000000000 0000000000000000 ffffffff00000301 0000000000000000
Feb 28 19:27:45 kernel: raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
Feb 28 19:27:45 kernel: page dumped because: nonzero _refcount
Feb 28 19:27:45 kernel: Modules linked in: ccm fuse arc4 nct6775 hwmon_vid amdgpu nls_iso8859_1 nls_cp437 edac_mce_amd vfat fat kvm_amd ccp rng_core kvm mt76x0u mt76x0_common mt76x02_usb irqbypass mt76_usb mt76x02_lib mt76 crct10dif_pclmul crc32_pclmul chash mac80211 amd_iommu_v2 ghash_clmulni_intel gpu_sched i2c_algo_bit ttm wmi_bmof snd_hda_codec_realtek snd_hda_codec_generic drm_kms_helper snd_hda_codec_hdmi snd_hda_intel drm snd_hda_codec aesni_intel snd_hda_core snd_hwdep aes_x86_64 crypto_simd snd_pcm cfg80211 cryptd mousedev snd_timer glue_helper pcspkr r8169 input_leds realtek agpgart libphy rfkill snd syscopyarea sysfillrect sysimgblt fb_sys_fops soundcore sp5100_tco k10temp i2c_piix4 wmi evdev gpio_amdpt pinctrl_amd mac_hid pcc_cpufreq acpi_cpufreq sg ip_tables x_tables ext4(E) crc32c_generic(E) crc16(E) mbcache(E) jbd2(E) fscrypto(E) sd_mod(E) hid_generic(E) usbhid(E) hid(E) dm_mod(E) serio_raw(E) atkbd(E) libps2(E) crc32c_intel(E) ahci(E) libahci(E) libata(E) xhci_pci(E) xhci_hcd(E)
Feb 28 19:27:45 kernel:  scsi_mod(E) i8042(E) serio(E) bcache(E) crc64(E)
Feb 28 19:27:45 kernel: CPU: 2 PID: 896 Comm: cinnamon Tainted: G    B   W   E     4.20.12-arch1-1-custom #1
Feb 28 19:27:45 kernel: Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./B450M Pro4, BIOS P1.20 06/26/2018
Feb 28 19:27:45 kernel: Call Trace:
Feb 28 19:27:45 kernel:  dump_stack+0x5c/0x80
Feb 28 19:27:45 kernel:  bad_page.cold.29+0x7f/0xb2
Feb 28 19:27:45 kernel:  __free_pages_ok+0x2c0/0x2d0
Feb 28 19:27:45 kernel:  skb_release_data+0x96/0x180
Feb 28 19:27:45 kernel:  __kfree_skb+0xe/0x20
Feb 28 19:27:45 kernel:  tcp_recvmsg+0x894/0xc60
Feb 28 19:27:45 kernel:  ? reuse_swap_page+0x120/0x340
Feb 28 19:27:45 kernel:  ? ptep_set_access_flags+0x23/0x30
Feb 28 19:27:45 kernel:  inet_recvmsg+0x5b/0x100
Feb 28 19:27:45 kernel:  __sys_recvfrom+0xc3/0x180
Feb 28 19:27:45 kernel:  ? handle_mm_fault+0x10a/0x250
Feb 28 19:27:45 kernel:  ? syscall_trace_enter+0x1d3/0x2d0
Feb 28 19:27:45 kernel:  ? __audit_syscall_exit+0x22a/0x290
Feb 28 19:27:45 kernel:  __x64_sys_recvfrom+0x24/0x30
Feb 28 19:27:45 kernel:  do_syscall_64+0x5b/0x170
Feb 28 19:27:45 kernel:  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Cc: stable at vger.kernel.org
Reported-and-tested-by: Jan Viktorin <jan.viktorin at gmail.com>
Reviewed-by: Alexander Duyck <alexander.h.duyck at linux.intel.com>
Signed-off-by: Stanislaw Gruszka <sgruszka at redhat.com>
---
v2: add comment 

 drivers/iommu/amd_iommu.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 6b0760dafb3e..696c78225dd1 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2604,7 +2604,11 @@ static int map_sg(struct device *dev, struct scatterlist *sglist,
 
 	/* Everything is mapped - write the right values into s->dma_address */
 	for_each_sg(sglist, s, nelems, i) {
-		s->dma_address += address + s->offset;
+		/* Add in the remaining piece of the scatter-gather offset that
+		 * was masked out when we were determining the physical address
+		 * via (sg_phys(s) & PAGE_MASK) earlier.
+		 */
+		s->dma_address += address + (s->offset & ~PAGE_MASK);
 		s->dma_length   = s->length;
 	}
 
-- 
2.7.5

[PATCH v2] iommu/amd: fix sg->dma_address for sg->offset bigger than PAGE_SIZE

[Joerg Roedel]

Hi Stanislaw,

thanks a lot for looking into this and tracking it down!

On Wed, Mar 13, 2019@10:03:17AM +0100, Stanislaw Gruszka wrote:
> -		s->dma_address += address + s->offset;
> +		/* Add in the remaining piece of the scatter-gather offset that
> +		 * was masked out when we were determining the physical address
> +		 * via (sg_phys(s) & PAGE_MASK) earlier.
> +		 */
> +		s->dma_address += address + (s->offset & ~PAGE_MASK);
>  		s->dma_length   = s->length;

Applied the patch for v5.1 (with an added Fixes-tag and a minor coding
style change) and will send it upstream soon.

Thanks again,

       Joerg

MT76x2U crashes XHCI driver on AMD Ryzen system

[Stanislaw Gruszka]

On Mon, Mar 11, 2019@09:43:19AM +0100, Stanislaw Gruszka wrote:
> > > However after fixing that mt76usb still did not work. To make things
> > > work we had to change rx frag size from 2048 to PAGE_SIZE and change
> > > virt_to_head_page() to virt_to_page() when setting SG's.
> >
> > > I think I understand why first change was needed. If we do 2 separate
> > > dma maps of 2 different buffers in single page i.e (PAGE + off=0
> > > and PAGE + off=2048) it causes problem. So either map_sg() return
> > > error which mt76usb does not handle correctly or there is issue
> > > in AMD IOMMU because two dma maps use the same page.
> 
> Any comment on that? Is fine or not to do 2 or more dma mappings
> within the same single page on AMD IOMMU? If not, is there any
> mechanism for drivers to find out about this limitation to prevent
> to prepare wrong SG buffers?

FTR: it was confirmed by Jan (bug reporter) the 2 or more dma mappings
within single page works with AMD IOMMU. Most likely it was needed
previously to workaround this sg->offset problem until proper fix to
AMD IOMMU was applied.

Stanislaw