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[34.127.79.33]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ae87fc548fsm10138264a91.4.2026.11.02.16.54.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 16:54:59 -0800 (PST) Date: Tue, 3 Nov 2026 00:54:54 +0000 From: David Matlack To: Mina Almasry Cc: Peter Xu , Alex Williamson , Andrew Morton , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Shuah Khan , Kevin Tian , Jason Gunthorpe , Raghavendra Rao Ananta , Vipin Sharma , Alex Mastro , Matt Evans Subject: Re: [PATCH v3 3/3] vfio: selftests: Test BAR write faults after clear_refs Message-ID: References: <20261102230445.3993629-1-almasrymina@google.com> <20261102230445.3993629-4-almasrymina@google.com> X-Mailing-List: kvm@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261102230445.3993629-4-almasrymina@google.com> On 2026-11-02 11:04 PM, Mina Almasry wrote: > Add a regression test in vfio_pci_device_test to verify that huge_fault > on writable MAP_SHARED VFIO PCI BAR mappings handles write faults after > soft-dirty tracking clears VM_SOFTDIRTY and downgrades vma->vm_page_prot > to read-only via /proc/self/clear_refs ("4"). > > Use vfio_pci_find_mem_bar() to locate a memory-backed BAR of at least > 2 MiB that is safe to read and write, and zap existing BAR mappings via > PCI_COMMAND_MEMORY before each sub-test to verify both: > > 1. Read-then-write fault sequence after clear_refs, exercising in-place > huge PMD/PUD write-protection upgrade via wp_huge_pmd()/wp_huge_pud(). > 2. Direct initial write fault on an unpopulated BAR VMA after clear_refs, > exercising vmf_insert_pfn_pmd()/vmf_insert_pfn_pud() with > FAULT_FLAG_WRITE set. > > Skip gracefully when the device has no known memory-backed BAR >= 2 MiB > or when /proc/self/clear_refs soft-dirty tracking (CONFIG_MEM_SOFT_DIRTY) > is unavailable. > > Suggested-by: Alex Williamson > Cc: David Matlack > Cc: Matt Evans > Signed-off-by: Mina Almasry Reviewed-by: David Matlack