linux-kernel - Re: [PATCH v6 00/16] x86/mtrr: fix handling with PAT but without MTRR

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Message-ID: <fe33476d-0ec1-16f1-5874-8a5ff1650c3f@suse.com>
Date:   Thu, 1 Jun 2023 10:19:01 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-hyperv@...r.kernel.org, linux-doc@...r.kernel.org,
        mikelley@...rosoft.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org, Jonathan Corbet <corbet@....net>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v6 00/16] x86/mtrr: fix handling with PAT but without MTRR

On 31.05.23 19:48, Borislav Petkov wrote:
> On Wed, May 31, 2023 at 04:20:08PM +0200, Juergen Gross wrote:
>> One other note: why does mtrr_cleanup() think that using 8 instead of 6
>> variable MTRRs would be an "optimal setting"?
> 
> Maybe the more extensive debug output below would help answer that...

Patch 2 wants this diff on top:

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 59b48bd8380c..ce254ca89c62 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -655,7 +655,7 @@ static bool set_mtrr_var_ranges(unsigned int index, struct 
mtrr_var_range *vr)
         bool changed = false;

         rdmsr(MTRRphysBase_MSR(index), lo, hi);
-       if ((vr->base_lo & MTRR_PHYSBASE_RSVD) != (lo & MTRR_PHYSBASE_RSVD)
+       if ((vr->base_lo & ~MTRR_PHYSBASE_RSVD) != (lo & ~MTRR_PHYSBASE_RSVD)
             || (vr->base_hi & ~phys_hi_rsvd) != (hi & ~phys_hi_rsvd)) {

                 mtrr_wrmsr(MTRRphysBase_MSR(index), vr->base_lo, vr->base_hi);
@@ -664,7 +664,7 @@ static bool set_mtrr_var_ranges(unsigned int index, struct 
mtrr_var_range *vr)

         rdmsr(MTRRphysMask_MSR(index), lo, hi);

-       if ((vr->mask_lo & MTRR_PHYSMASK_RSVD) != (lo & MTRR_PHYSMASK_RSVD)
+       if ((vr->mask_lo & ~MTRR_PHYSMASK_RSVD) != (lo & ~MTRR_PHYSMASK_RSVD)
             || (vr->mask_hi & ~phys_hi_rsvd) != (hi & ~phys_hi_rsvd)) {
                 mtrr_wrmsr(MTRRphysMask_MSR(index), vr->mask_lo, vr->mask_hi);
                 changed = true;



Juergen

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