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[34.83.236.195]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-12c345b6208sm22430017c88.8.2026.04.14.16.55.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2026 16:55:23 -0700 (PDT) Date: Tue, 14 Apr 2026 23:55:19 +0000 From: Samiullah Khawaja To: Weinan Liu Cc: iommu@lists.linux.dev, jgg@nvidia.com, joro@8bytes.org, patches@lists.linux.dev, robin.murphy@arm.com, suravee.suthikulpanit@amd.com, wei.w.wang@hotmail.com, will@kernel.org, kpsingh@kernel.org, josef@toxicpanda.com Subject: Re: [PATCH v1 1/1] iommu/amd: Don't split flush for amd_iommu_domain_flush_all() Message-ID: References: <20260414210626.2097722-1-wnliu@google.com> <20260414210626.2097722-2-wnliu@google.com> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20260414210626.2097722-2-wnliu@google.com> On Tue, Apr 14, 2026 at 09:06:26PM +0000, Weinan Liu wrote: >We have observed multiple full invalidations occurring during device >detach when we are done using the vfio-device. > >blocked_domain_attach_device() > -> detach_device() > -> amd_iommu_domain_flush_all() > -> amd_iommu_domain_flush_pages(..., CMD_INV_IOMMU_ALL_PAGES_ADDRESS) > > while (size != 0) { > > -> __domain_flush_pages( flush_size /* power of 2 flush_size */) > -> domain_flush_pages_v1() > -> build_inv_iommu_pages() > -> build_inv_address() > > } > >build_inv_address() will trigger a full invalidation if the chunk >size > (1 << 51). Consequently, the guest will issue multiple full >invalidations for a single call to amd_iommu_domain_flush_all() > >Without this patch, we will see 10 time instead of 1 time full >invalidations for every amd_iommu_domain_flush_all(). > >Fixes: a270be1b3fdf ("iommu/amd: Use only natural aligned flushes in a VM") > >Suggested-by: Josef Bacik >Suggested-by: Jason Gunthorpe >Signed-off-by: Weinan Liu >--- > drivers/iommu/amd/iommu.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > >diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c >index 760d5f4623b5..bcec8721d228 100644 >--- a/drivers/iommu/amd/iommu.c >+++ b/drivers/iommu/amd/iommu.c >@@ -1769,7 +1769,8 @@ void amd_iommu_domain_flush_pages(struct protection_domain *domain, > { > lockdep_assert_held(&domain->lock); > >- if (likely(!amd_iommu_np_cache)) { >+ if (likely(!amd_iommu_np_cache) || >+ size == CMD_INV_IOMMU_ALL_PAGES_ADDRESS) { > __domain_flush_pages(domain, address, size); > > /* Wait until IOMMU TLB and all device IOTLB flushes are complete */ >-- >2.54.0.rc0.605.g598a273b03-goog > > Reviewed-by: Samiullah Khawaja