linux-kernel - Re: AMD boot woe due to "x86/mm: Cleanup pgprot_4k_2_large() and pgprot_large_2

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Date:   Wed, 22 Apr 2020 19:01:16 +0200
From:   Christoph Hellwig <hch@....de>
To:     Qian Cai <cai@....pw>
Cc:     Christoph Hellwig <hch@....de>, Borislav Petkov <bp@...e.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: AMD boot woe due to "x86/mm: Cleanup pgprot_4k_2_large() and
 pgprot_large_2_4k()"

On Wed, Apr 22, 2020 at 11:55:54AM -0400, Qian Cai wrote:
> Reverted the linux-next commit and its dependency,
> 
> a85573f7e741 ("x86/mm: Unexport __cachemode2pte_tbl”)
> 9e294786c89a (“x86/mm: Cleanup pgprot_4k_2_large() and pgprot_large_2_4k()”)
> 
> fixed crashes or hard reset on AMD machines during boot that have been flagged by
> KASAN in different forms indicating some sort of memory corruption with this config,

Interesting.  Your config seems to boot fine in my VM until the point
where the lack of virtio-blk support stops it from mounting the root
file system.

Looking at the patch I found one bug, although that should not affect
your config (it should use the pgprotval_t type), and one difference
that could affect code generation, although I prefer the new version
(use of __pgprot vs a local variable + pgprot_val()).

Two patches attached, can you try them?

View attachment "0001-x86-Use-pgprotval_t-in-protval_4k_2_large-and-pgprot.patch" of type "text/x-patch" (1379 bytes)

View attachment "0002-foo.patch" of type "text/x-patch" (1208 bytes)