linux-kernel - Re: [PATCH v2 5/8] x86/mtrr: revert commit 90b926e68f50

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Message-ID: <9046a3cb-928a-5476-1e72-63bd197c039e@leemhuis.info>
Date:   Fri, 10 Feb 2023 19:59:41 +0100
From:   "Linux regression tracking (Thorsten Leemhuis)" 
        <regressions@...mhuis.info>
To:     Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Cc:     lists@...dbynature.de, mikelley@...rosoft.com,
        torvalds@...ux-foundation.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 5/8] x86/mtrr: revert commit 90b926e68f50

Hi, this is your Linux kernel regression tracker.

On 09.02.23 08:22, Juergen Gross wrote:
> Commit 90b926e68f50 ("x86/pat: Fix pat_x_mtrr_type() for MTRR disabled
> case") has introduced a regression with Xen.
> 
> Revert the patch.

That regression you refer to is afaics one I'm tracking[1] that was
introduced this cycle. That makes me wonder: could this patch be applied
directly to fix the issue quickly? Or are patches 1 to 4 needed as well
(or the whole series?) to avoid other problems?

Ciao, Thorsten

[1]
https://lore.kernel.org/all/4fe9541e-4d4c-2b2a-f8c8-2d34a7284930@nerdbynature.de/

P.S.: BTW; let me tell regzbot to monitor this thread:

#regzbot ^backmonitor:
https://lore.kernel.org/all/4fe9541e-4d4c-2b2a-f8c8-2d34a7284930@nerdbynature.de/


> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
>  arch/x86/mm/pat/memtype.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
> index fb4b1b5e0dea..46de9cf5c91d 100644
> --- a/arch/x86/mm/pat/memtype.c
> +++ b/arch/x86/mm/pat/memtype.c
> @@ -387,8 +387,7 @@ static unsigned long pat_x_mtrr_type(u64 start, u64 end,
>  		u8 mtrr_type, uniform;
>  
>  		mtrr_type = mtrr_type_lookup(start, end, &uniform);
> -		if (mtrr_type != MTRR_TYPE_WRBACK &&
> -		    mtrr_type != MTRR_TYPE_INVALID)
> +		if (mtrr_type != MTRR_TYPE_WRBACK)
>  			return _PAGE_CACHE_MODE_UC_MINUS;
>  
>  		return _PAGE_CACHE_MODE_WB;