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Subject[PATCH 5.9 026/152] iommu/vt-d: Dont read VCCAP register unless it exists
Date
From: David Woodhouse <dwmw@amazon.co.uk>

commit d76b42e92780c3587c1a998a3a943b501c137553 upstream.

My virtual IOMMU implementation is whining that the guest is reading a
register that doesn't exist. Only read the VCCAP_REG if the corresponding
capability is set in ECAP_REG to indicate that it actually exists.

Fixes: 3375303e8287 ("iommu/vt-d: Add custom allocator for IOASID")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Liu Yi L <yi.l.liu@intel.com>
Cc: stable@vger.kernel.org # v5.7+
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/de32b150ffaa752e0cff8571b17dfb1213fbe71c.camel@infradead.org
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/iommu/intel/dmar.c | 3 ++-
drivers/iommu/intel/iommu.c | 4 ++--
2 files changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -964,7 +964,8 @@ static int map_iommu(struct intel_iommu
warn_invalid_dmar(phys_addr, " returns all ones");
goto unmap;
}
- iommu->vccap = dmar_readq(iommu->reg + DMAR_VCCAP_REG);
+ if (ecap_vcs(iommu->ecap))
+ iommu->vccap = dmar_readq(iommu->reg + DMAR_VCCAP_REG);

/* the registers might be more than one page */
map_size = max_t(int, ecap_max_iotlb_offset(iommu->ecap),
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1798,7 +1798,7 @@ static void free_dmar_iommu(struct intel
if (ecap_prs(iommu->ecap))
intel_svm_finish_prq(iommu);
}
- if (ecap_vcs(iommu->ecap) && vccap_pasid(iommu->vccap))
+ if (vccap_pasid(iommu->vccap))
ioasid_unregister_allocator(&iommu->pasid_allocator);

#endif
@@ -3177,7 +3177,7 @@ static void register_pasid_allocator(str
* is active. All vIOMMU allocators will eventually be calling the same
* host allocator.
*/
- if (!ecap_vcs(iommu->ecap) || !vccap_pasid(iommu->vccap))
+ if (!vccap_pasid(iommu->vccap))
return;

pr_info("Register custom PASID allocator\n");

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