Re: [BUG 5.14] arm64/mm: dma memory mapping fails (in some cases)
From: Will Deacon <will@kernel.org>
Date: 2021-08-25 10:32:31
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linux-arm-kernel, lkml
On Wed, Aug 25, 2021 at 11:28:56AM +0100, Will Deacon wrote:
On Wed, Aug 25, 2021 at 11:20:46AM +0100, Catalin Marinas wrote:quoted
Given how later we are in the -rc cycle, I suggest we revert Anshuman's commit 16c9afc77660 ("arm64/mm: drop HAVE_ARCH_PFN_VALID") and try to assess the implications in 5.15 (the patch doesn't seem to have the arm64 maintainers' ack anyway ;)).I'll stick the revert (below) into kernelci now so we can get some coverage in case it breaks something else.
Bah, having said that...
quoted hunk ↗ jump to hunk
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index fcb535560028..ee70f21a79d5 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h@@ -1463,15 +1463,6 @@ static inline int pfn_valid(unsigned long pfn) { struct mem_section *ms; - /* - * Ensure the upper PAGE_SHIFT bits are clear in the - * pfn. Else it might lead to false positives when - * some of the upper bits are set, but the lower bits - * match a valid pfn. - */ - if (PHYS_PFN(PFN_PHYS(pfn)) != pfn) - return 0; -
I suppose we should leave this bit as-is, since the whole point here is trying to minimise the impact on other architectures. Will