linux-kernel - Re: [PATCH] x86/mm/sme: Fix definition of PMD_FLAGS_DEC

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Date:   Mon, 9 Nov 2020 16:42:18 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86/mm/sme: Fix definition of PMD_FLAGS_DEC_WP

On Mon, Nov 09, 2020 at 02:41:48PM -0600, Tom Lendacky wrote:
> On 11/9/20 11:35 AM, Arvind Sankar wrote:
> > The PAT bit is in different locations for 4k and 2M/1G page table
> > entries.
> > 
> > Add a definition for _PAGE_LARGE_CACHE_MASK to represent the three
> > caching bits (PWT, PCD, PAT), similar to _PAGE_CACHE_MASK for 4k pages,
> > and use it in the definition of PMD_FLAGS_DEC_WP to get the correct PAT
> > index for write-protected pages.
> > 
> > Remove a duplication definition of _PAGE_PAT_LARGE.
> > 
> > Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
> 
> Fixes: tag?

It's been broken since it was added in

  6ebcb060713f ("x86/mm: Add support to encrypt the kernel in-place")

but the code has been restructured since then. I think it should be
backportable to 4.19.x if you want, except for that "duplication
definition"[sic] I removed, which was only added in v5.6. Do I need to
split that out into a separate patch?

> 
> Tested-by: Tom Lendacky <thomas.lendacky@....com>
> 
> > ---
> >  arch/x86/include/asm/pgtable_types.h | 3 +--
> >  arch/x86/mm/mem_encrypt_identity.c   | 4 ++--
> >  2 files changed, 3 insertions(+), 4 deletions(-)
> >