Re: [RFC PATCH RESEND] iommu: intel: apply quirk_iommu_igfx for 8086:0044 (QM57/QS57)

[Baolu Lu]

On 4/18/25 11:07, Baolu Lu wrote:
> On 1/20/25 17:35, Mingcong Bai wrote:
> > (I'm not very confident about the approach of this patch but I failed to
> > find a better way to address the issue I have on hand, so please consider
> > this patch as an RFC...)
> >
> > On the Lenovo ThinkPad X201, when Intel VT-d is enabled in the BIOS, the
> > kernel boots with errors related to DMAR, the graphical interface 
> > appeared
> > quite choppy, and the system resets erratically within a minute after it
> > booted:
> >
> > DMAR: DRHD: handling fault status reg 3
> > DMAR: [DMA Write NO_PASID] Request device [00:02.0] fault addr 0xb97ff000
> > [fault reason 0x05] PTE Write access is not set
> >
> > Upon comparing boot logs with VT-d on/off, I found that the Intel 
> > Calpella
> > quirk (`quirk_calpella_no_shadow_gtt()') correctly applied the igfx IOMMU
> > disable/quirk correctly:
> >
> > pci 0000:00:00.0: DMAR: BIOS has allocated no shadow GTT; disabling IOMMU
> > for graphics
> >
> > Whereas with VT-d on, it went into the "else" branch, which then
> > triggered the DMAR handling fault above:
> >
> > ... else if (!disable_igfx_iommu) {
> >     /* we have to ensure the gfx device is idle before we flush */
> >     pci_info(dev, "Disabling batched IOTLB flush on Ironlake\n");
> >     iommu_set_dma_strict();
> > }
> >
> > Now, this is not exactly scientific, but moving 0x0044 to 
> > quirk_iommu_igfx
> > seems to have fixed the aforementioned issue. Running a few `git blame'
> > runs on the function, I have found that the quirk was originally
> > introduced as a fix specific to ThinkPad X201:
> >
> > commit 9eecabcb9a92 ("intel-iommu: Abort IOMMU setup for igfx if BIOS 
> > gave
> > no shadow GTT space")
> >
> > Which was later revised twice to the "else" branch we saw above:
> >
> > - 2011: commit 6fbcfb3e467a ("intel-iommu: Workaround IOTLB hang on
> >    Ironlake GPU")
> > - 2024: commit ba00196ca41c ("iommu/vt-d: Decouple igfx_off from graphic
> >    identity mapping")
> >
> > I'm uncertain whether further testings on this particular laptops were
> > done in 2011 and (honestly I'm not sure) 2024, but I would be happy to do
> > some distro-specific testing if that's what would be required to verify
> > this patch.
> >
> > P.S., I also see IDs 0x0040, 0x0062, and 0x006a listed under the same
> > `quirk_calpella_no_shadow_gtt()' quirk, but I'm not sure how similar 
> > these
> > chipsets are (if they share the same issue with VT-d or even, indeed, if
> > this issue is specific to a bug in the Lenovo BIOS). With regards to
> > 0x0062, it seems to be a Centrino wireless card, but not a chipset?
> >
> > I have also listed a couple (distro and kernel) bug reports below as
> > references (some of them are from 7-8 years ago!), as they seem to be
> > similar issue found on different Westmere/Ironlake, Haswell, and 
> > Broadwell
> > hardware setups.
> >
> > Link:https://bugzilla.kernel.org/show_bug.cgi?id=197029
> > Link:https://groups.google.com/g/qubes-users/c/4NP4goUds2c?pli=1
> > Link:https://bugs.archlinux.org/task/65362
> > Link:https://bbs.archlinux.org/viewtopic.php?id=230323
> > Reported-by: Wenhao Sun<weiguangtwk@xxxxxxxxxxx>
> > Signed-off-by: Mingcong Bai<jeffbai@xxxxxxx>
> > ---
> >   drivers/iommu/intel/iommu.c | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
>
> Queued for v6.15-rc. Thank you!

Please ignore this. I picked the latest one instead.

https://lore.kernel.org/r/20250415133330.12528-1-jeffbai@xxxxxxx

Sorry for the inconvenience.