From: Jan Beulich <jbeulich@suse.com>
To: Chuck Zmudzinski <brchuckz@aol.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Dan Williams <dan.j.williams@intel.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Jane Chu <jane.chu@oracle.com>,
Tianyu Lan <Tianyu.Lan@microsoft.com>,
Randy Dunlap <rdunlap@infradead.org>,
Sean Christopherson <seanjc@google.com>,
Juergen Gross <jgross@suse.com>,
xen-devel@lists.xenproject.org, stable@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] Subject: x86/PAT: Report PAT on CPUs that support PAT without MTRR
Date: Wed, 13 Jul 2022 08:18:05 +0200 [thread overview]
Message-ID: <e0faeb99-6c32-a836-3f6b-269318a6b5a6@suse.com> (raw)
In-Reply-To: <9d5070ae4f3e956a95d3f50e24f1a93488b9ff52.1657671676.git.brchuckz@aol.com>
On 13.07.2022 03:36, Chuck Zmudzinski wrote:
> v2: *Add force_pat_disabled variable to fix "nopat" on Xen PV (Jan Beulich)
> *Add the necessary code to incorporate the "nopat" fix
> *void init_cache_modes(void) -> void __init init_cache_modes(void)
> *Add Jan Beulich as Co-developer (Jan has not signed off yet)
> *Expand the commit message to include relevant parts of the commit
> message of Jan Beulich's proposed patch for this problem
> *Fix 'else if ... {' placement and indentation
> *Remove indication the backport to stable branches is only back to 5.17.y
>
> I think these changes address all the comments on the original patch
>
> I added Jan Beulich as a Co-developer because Juergen Gross asked me to
> include Jan's idea for fixing "nopat" that was missing from the first
> version of the patch.
You've sufficiently altered this change to clearly no longer want my
S-o-b; unfortunately in fact I think you broke things:
> @@ -292,7 +294,7 @@ void init_cache_modes(void)
> rdmsrl(MSR_IA32_CR_PAT, pat);
> }
>
> - if (!pat) {
> + if (!pat || pat_force_disabled) {
By checking the new variable here ...
> /*
> * No PAT. Emulate the PAT table that corresponds to the two
> * cache bits, PWT (Write Through) and PCD (Cache Disable).
> @@ -313,6 +315,16 @@ void init_cache_modes(void)
> */
> pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) |
> PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC);
... you put in place a software view which doesn't match hardware. I
continue to think that ...
> + } else if (!pat_bp_enabled) {
... the variable wants checking here instead (at which point, yes,
this comes quite close to simply being a v2 of my original patch).
By using !pat_bp_enabled here you actually broaden where the change
would take effect. Iirc Boris had asked to narrow things (besides
voicing opposition to this approach altogether). Even without that
request I wonder whether you aren't going to far with this.
Jan
next prev parent reply other threads:[~2022-07-13 6:18 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <9d5070ae4f3e956a95d3f50e24f1a93488b9ff52.1657671676.git.brchuckz.ref@aol.com>
2022-07-13 1:36 ` [PATCH v2] Subject: x86/PAT: Report PAT on CPUs that support PAT without MTRR Chuck Zmudzinski
2022-07-13 4:12 ` Juergen Gross
2022-07-13 6:18 ` Jan Beulich [this message]
2022-07-13 8:51 ` Chuck Zmudzinski
2022-07-13 9:09 ` Jan Beulich
2022-07-13 10:36 ` Chuck Zmudzinski
2022-07-13 11:10 ` Chuck Zmudzinski
2022-07-13 13:34 ` Jan Beulich
2022-07-13 13:45 ` Juergen Gross
2022-07-13 17:01 ` Chuck Zmudzinski
2022-07-13 19:07 ` Chuck Zmudzinski
2022-07-13 19:22 ` Chuck Zmudzinski
2022-07-13 19:38 ` Chuck Zmudzinski
2022-07-13 22:12 ` Chuck Zmudzinski
2022-07-13 13:49 ` Chuck Zmudzinski
2022-07-13 13:52 ` Jan Beulich
2022-07-13 15:02 ` Chuck Zmudzinski
2022-07-13 15:05 ` Jan Beulich
2022-07-14 5:30 ` Thorsten Leemhuis
2022-07-15 2:07 ` Chuck Zmudzinski
2022-07-15 5:00 ` Thorsten Leemhuis
2022-07-15 10:05 ` Jan Beulich
2022-07-15 19:53 ` Chuck Zmudzinski
2022-07-16 11:02 ` Chuck Zmudzinski
2022-07-18 6:07 ` Jan Beulich
2022-07-18 11:31 ` Chuck Zmudzinski
2022-07-18 11:39 ` Jan Beulich
2022-07-18 11:45 ` Chuck Zmudzinski
2022-07-18 12:12 ` Chuck Zmudzinski
2022-08-17 16:39 ` Chuck Zmudzinski
2022-07-14 5:40 ` Juergen Gross
2022-07-14 6:28 ` Jan Beulich
2022-07-15 2:19 ` Chuck Zmudzinski
2022-07-15 2:53 ` Chuck Zmudzinski
2022-07-15 2:58 ` Chuck Zmudzinski
2022-07-15 4:22 ` Juergen Gross
2022-07-15 4:42 ` Chuck Zmudzinski
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