From: Peter Zijlstra <peterz@infradead.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
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x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
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"Paul E. McKenney" <paulmck@kernel.org>,
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Xin Li <xin3.li@intel.com>,
"Mike Rapoport (IBM)" <rppt@kernel.org>,
Brijesh Singh <brijesh.singh@amd.com>,
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Arnaldo Carvalho de Melo <acme@redhat.com>,
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Subject: Re: [PATCH v4 03/16] x86/alternatives: Disable LASS when patching kernel alternatives
Date: Thu, 11 Jul 2024 10:14:59 +0200 [thread overview]
Message-ID: <20240711081459.GE4587@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <cqacx3crogegwyslm25kwcdcezgg2n44lhy3mg5qkka3vgn4xa@lhqsoseyduus>
On Thu, Jul 11, 2024 at 01:33:23AM +0300, Kirill A. Shutemov wrote:
> On Wed, Jul 10, 2024 at 07:18:36PM +0200, Borislav Petkov wrote:
> > On Wed, Jul 10, 2024 at 07:06:39PM +0300, Alexander Shishkin wrote:
> > > static void text_poke_memcpy(void *dst, const void *src, size_t len)
> > > {
> > > - memcpy(dst, src, len);
> > > + stac();
> > > + __inline_memcpy(dst, src, len);
> > > + clac();
> >
> > I think you need LASS-specific stac()/clac() or an alternative_2 or so. You
> > can't cause that perf penalty on !LASS machines.
>
> Hm. Do we have text_poke() in hot path?
>
> Even if we do, I doubt flipping AC flag would make any performance
> difference in context of all locking and TLB flushing we do in this
> codepath.
The one where performance might matter is text_poke_early(), the full
fat one is comically slow as you point out.
next prev parent reply other threads:[~2024-07-11 8:15 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-10 16:06 [PATCH v4 00/16] Enable Linear Address Space Separation support Alexander Shishkin
2024-07-10 16:06 ` [PATCH v4 01/16] x86/cpu: Enumerate the LASS feature bits Alexander Shishkin
2025-05-13 3:08 ` Xin Li
2024-07-10 16:06 ` [PATCH v4 02/16] x86/asm: Introduce inline memcpy and memset Alexander Shishkin
2024-07-11 8:13 ` Peter Zijlstra
2024-07-10 16:06 ` [PATCH v4 03/16] x86/alternatives: Disable LASS when patching kernel alternatives Alexander Shishkin
2024-07-10 17:18 ` Borislav Petkov
2024-07-10 22:33 ` Kirill A. Shutemov
2024-07-10 23:05 ` Dave Hansen
2024-07-11 8:16 ` Peter Zijlstra
2024-07-11 10:32 ` Kirill A. Shutemov
2024-07-11 14:03 ` Dave Hansen
2024-07-11 1:23 ` Borislav Petkov
2024-07-11 8:14 ` Peter Zijlstra [this message]
2024-07-10 16:06 ` [PATCH v4 04/16] x86/cpu: Enable LASS during CPU initialization Alexander Shishkin
2024-07-10 16:06 ` [PATCH v4 05/16] x86/cpu: Remove redundant comment during feature setup Alexander Shishkin
2024-07-10 17:21 ` Borislav Petkov
2024-07-10 16:06 ` [PATCH v4 06/16] init/main.c: Move EFI runtime service initialization to x86/cpu Alexander Shishkin
2024-07-10 16:06 ` [PATCH v4 07/16] x86/cpu: Defer CR pinning setup until after EFI initialization Alexander Shishkin
2024-07-11 8:11 ` Peter Zijlstra
2024-07-11 10:37 ` Kirill A. Shutemov
2024-07-10 16:06 ` [PATCH v4 08/16] x86/vsyscall: Reorganize the #PF emulation code Alexander Shishkin
2024-07-10 16:06 ` [PATCH v4 09/16] x86/traps: Consolidate user fixups in exc_general_protection() Alexander Shishkin
2024-07-10 16:06 ` [PATCH v4 10/16] x86/vsyscall: Add vsyscall emulation for #GP Alexander Shishkin
2024-07-10 16:06 ` [PATCH v4 11/16] x86/vsyscall: Disable LASS if vsyscall mode is set to EMULATE Alexander Shishkin
2024-07-10 16:06 ` [PATCH v4 12/16] x86/vsyscall: Document the fact that vsyscall=emulate disables LASS Alexander Shishkin
2024-07-10 16:06 ` [PATCH v4 13/16] x86/cpu: Set LASS CR4 bit as pinning sensitive Alexander Shishkin
2024-07-10 16:06 ` [PATCH v4 14/16] x86/traps: Communicate a LASS violation in #GP message Alexander Shishkin
2024-07-10 16:06 ` [PATCH v4 15/16] efi: Disable LASS around set_virtual_address_map call Alexander Shishkin
2024-07-10 16:06 ` [PATCH v4 16/16] x86/cpu: Make LAM depend on LASS Alexander Shishkin
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