Hi Baolu,
On Tue, 7 Feb 2023 15:10:48 +0800, Baolu Lu baolu.lu@linux.intel.com wrote:
On 2023/2/7 1:25, Jacob Pan wrote:
drivers/iommu/intel/iommu.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index 59df7e42fd53..b4878c7ac008 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -1976,6 +1976,12 @@ static int domain_context_mapping_one(struct dmar_domain *domain, pds = context_get_sm_pds(table); context->lo = (u64)virt_to_phys(table->table) | context_pdts(pds);
/** Scalable-mode PASID directory pointer is notsnooped if the
* coherent bit is not set.*/if (!ecap_coherent(iommu->ecap))clflush_cache_range(table->table, sizeof(void*));
This isn't comprehensive. The clflush should be called whenever the pasid directory table is allocated or updated.
allocate a pasid table does not mean it gets used by iommu hw, not until it is programmed into context entry.
Hi Jacob,
This page is used by the device, and the device's access to this memory is not coherent. So after the page is allocated, any changes made by the CPU to this page must be written back to the real memory.
This patch only flushes the first 8 bytes of the table. That's not enough.
make sense, thanks for the explanation.
Be aware that page allocation also requires a clflush, because at least __GFP_ ZERO implies modification to page.
Yes, zeroing dir page does change it but I think if we intercept every update to the directory entry, it should be sufficient?
will send an updated version.
Thanks,
Jacob