mirror of https://github.com/torvalds/linux.git
2c8a7c66c9
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
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|---|---|---|
| .. | ||
| Kconfig | ||
| Makefile | ||
| cache.c | ||
| debugfs.c | ||
| dmar.c | ||
| iommu.c | ||
| iommu.h | ||
| irq_remapping.c | ||
| nested.c | ||
| pasid.c | ||
| pasid.h | ||
| perf.c | ||
| perf.h | ||
| perfmon.c | ||
| perfmon.h | ||
| prq.c | ||
| svm.c | ||
| trace.c | ||
| trace.h | ||