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Tsirkin" , Miguel Ojeda , Robin Murphy , rust-for-linux@vger.kernel.org, Sagi Grimberg , Stefano Stabellini , Steven Rostedt , virtualization@lists.linux.dev, Will Deacon , xen-devel@lists.xenproject.org Subject: Re: [PATCH v1 08/16] kmsan: convert kmsan_handle_dma to use physical addresses Message-ID: <20250814133106.GE310013@unreal> References: <5b40377b621e49ff4107fa10646c828ccc94e53e.1754292567.git.leon@kernel.org> <20250807122115.GH184255@nvidia.com> <20250813150718.GB310013@unreal> <20250814121316.GC699432@nvidia.com> <20250814123506.GD310013@unreal> <20250814124448.GE699432@nvidia.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250814124448.GE699432@nvidia.com> On Thu, Aug 14, 2025 at 09:44:48AM -0300, Jason Gunthorpe wrote: > On Thu, Aug 14, 2025 at 03:35:06PM +0300, Leon Romanovsky wrote: > > > Then check attrs here, not pfn_valid. > > > > attrs are not available in kmsan_handle_dma(). I can add it if you prefer. > > That makes more sense to the overall design. The comments I gave > before were driving at a promise to never try to touch a struct page > for ATTR_MMIO and think this should be comphrensive to never touching > a struct page even if pfnvalid. > > > > > So let's keep this patch as is. > > > > > > Still need to fix the remarks you clipped, do not check PageHighMem > > > just call kmap_local_pfn(). All thie PageHighMem stuff is new to this > > > patch and should not be here, it is the wrong way to use highmem. > > > > Sure, thanks > > I am wondering if there is some reason it was written like this in the > first place. Maybe we can't even do kmap here.. So perhaps if there is > not a strong reason to change it just continue to check pagehighmem > and fail. > > if (!(attrs & ATTR_MMIO) && PageHighMem(phys_to_page(phys))) > return; Does this version good enough? There is no need to call to kmap_local_pfn() if we prevent PageHighMem pages. diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c index eab7912a3bf0..d9cf70f4159c 100644 --- a/mm/kmsan/hooks.c +++ b/mm/kmsan/hooks.c @@ -337,13 +337,13 @@ static void kmsan_handle_dma_page(const void *addr, size_t size, /* Helper function to handle DMA data transfers. */ void kmsan_handle_dma(phys_addr_t phys, size_t size, - enum dma_data_direction dir) + enum dma_data_direction dir, unsigned long attrs) { u64 page_offset, to_go, addr; struct page *page; void *kaddr; - if (!pfn_valid(PHYS_PFN(phys))) + if ((attrs & ATTR_MMIO) || PageHighMem(phys_to_page(phys))) return; page = phys_to_page(phys); @@ -357,19 +357,12 @@ void kmsan_handle_dma(phys_addr_t phys, size_t size, while (size > 0) { to_go = min(PAGE_SIZE - page_offset, (u64)size); - if (PageHighMem(page)) - /* Handle highmem pages using kmap */ - kaddr = kmap_local_page(page); - else - /* Lowmem pages can be accessed directly */ - kaddr = page_address(page); + /* Lowmem pages can be accessed directly */ + kaddr = page_address(page); addr = (u64)kaddr + page_offset; kmsan_handle_dma_page((void *)addr, to_go, dir); - if (PageHighMem(page)) - kunmap_local(page); - phys += to_go; size -= to_go; (END) > > Jason >