Hi Lu,
On Sun, 7 Apr 2024 22:42:32 +0800, Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
wrote:
The Caching Mode (CM) of the Intel IOMMU indicates if the hardwareI agree with the changes below, what about this CM check:
implementation caches not-present or erroneous translation-structure
entries except the first-stage translation. The caching mode is
unrelated to the device TLB , therefore there is no need to check
it before a device TLB invalidation operation.
Before the scalable mode is introduced, caching mode is treated as
an indication that the driver is running in a VM guest. This is just
a software contract as shadow page table is the only way to implement
a virtual IOMMU. But the VT-d spec doesn't state this anywhere. After
the scalable mode is introduced, this doesn't stand for anymore, as
caching mode is not relevant for the first-stage translation. A virtual
IOMMU implementation is free to support first-stage translation only
with caching mode cleared.
Remove the caching mode check before device TLB invalidation to ensure
compatibility with the scalable mode use cases.
/* Notification for newly created mappings */
static void __mapping_notify_one(struct intel_iommu *iommu, struct dmar_domain *domain,
unsigned long pfn, unsigned int pages)
{
/*
* It's a non-present to present mapping. Only flush if caching mode
* and second level.
*/
if (cap_caching_mode(iommu->cap) && !domain->use_first_level)
iommu_flush_iotlb_psi(iommu, domain, pfn, pages, 0, 1);
We are still tying devTLB flush to CM=1, no?
If we are running in the guest with second level page table (shadowed), can
we decide if devTLB flush is needed based on ATS enable just as the rest of
the cases?