Re: [PATCH v1 08/16] kmsan: convert kmsan_handle_dma to use physical addresses
From: Leon Romanovsky <leon@kernel.org>
Date: 2025-08-14 13:31:12
Also in:
linux-block, linux-doc, linux-iommu, linux-mm, linux-nvme, linux-trace-kernel, linuxppc-dev, lkml, rust-for-linux, xen-devel
Subsystem:
kmsan, memory management, the rest · Maintainers:
Alexander Potapenko, Andrew Morton, Linus Torvalds
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:quoted
quoted
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.quoted
quoted
quoted
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, thanksI 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