From: Peter Zijlstra <peterz@infradead.org>
To: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
David.Kaplan@amd.com, Andrew.Cooper3@citrix.com,
jpoimboe@kernel.org, gregkh@linuxfoundation.org,
nik.borisov@suse.com
Subject: Re: [PATCH v2 10/11] x86/alternatives: Simplify ALTERNATIVE_n()
Date: Tue, 12 Sep 2023 11:27:09 +0200 [thread overview]
Message-ID: <20230912092709.GE35261@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20230910144227.GAZP3V0/mQ73C2hx/l@fat_crate.local>
On Sun, Sep 10, 2023 at 04:42:27PM +0200, Borislav Petkov wrote:
> On Sat, Sep 09, 2023 at 11:25:54AM +0200, Peter Zijlstra wrote:
> > So what you end up with is:
> >
> > 661:
> > "one byte orig insn"
> > "one nop because alt1 is 2 bytes"
> > "one nop because alt2 is 3 bytes"
> >
> > right?
>
> Right.
>
> > This becomes more of a problem with your example above where the
> > respective lengths are 0, 5, 16. In that case, when you patch 5, you'll
> > leave 11 single nops in there.
>
> Well, I know what you mean but the code handles that gracefully and it
> works. Watch this:
Aah, because we run optimize_nops() for all alternatives, irrespective
of it being selected. And thus also for the longest and then that'll fix
things up.
OK, let me check on objtool.
next prev parent reply other threads:[~2023-09-12 9:27 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-14 11:44 [PATCH v2 00/11] Fix up SRSO stuff Peter Zijlstra
2023-08-14 11:44 ` [PATCH v2 01/11] x86/cpu: Fixup __x86_return_thunk Peter Zijlstra
2023-08-16 7:55 ` [tip: x86/urgent] x86/cpu: Fix __x86_return_thunk symbol type tip-bot2 for Peter Zijlstra
2023-08-14 11:44 ` [PATCH v2 02/11] x86/cpu: Fix up srso_safe_ret() and __x86_return_thunk() Peter Zijlstra
2023-08-16 7:55 ` [tip: x86/urgent] " tip-bot2 for Peter Zijlstra
2023-08-14 11:44 ` [PATCH v2 03/11] objtool/x86: Fix SRSO mess Peter Zijlstra
2023-08-14 12:54 ` Andrew.Cooper3
2023-08-16 7:55 ` [tip: x86/urgent] " tip-bot2 for Peter Zijlstra
2023-08-16 11:59 ` Peter Zijlstra
2023-08-16 20:31 ` Josh Poimboeuf
2023-08-16 22:08 ` [PATCH] objtool/x86: Fixup frame-pointer vs rethunk Peter Zijlstra
2023-08-16 22:22 ` Josh Poimboeuf
2023-08-17 8:39 ` [tip: x86/urgent] " tip-bot2 for Peter Zijlstra
2023-08-14 11:44 ` [PATCH v2 04/11] x86/alternative: Make custom return thunk unconditional Peter Zijlstra
2023-08-16 7:55 ` [tip: x86/urgent] " tip-bot2 for Peter Zijlstra
2023-08-14 11:44 ` [PATCH v2 05/11] x86/cpu: Clean up SRSO return thunk mess Peter Zijlstra
2023-08-14 13:02 ` Borislav Petkov
2023-08-14 17:48 ` Borislav Petkov
2023-08-15 21:29 ` Nathan Chancellor
2023-08-15 22:43 ` Peter Zijlstra
2023-08-16 7:38 ` Borislav Petkov
2023-08-16 14:52 ` Nathan Chancellor
2023-08-16 15:08 ` Borislav Petkov
2023-08-16 7:55 ` [tip: x86/urgent] " tip-bot2 for Peter Zijlstra
2023-08-16 18:58 ` Nathan Chancellor
2023-08-16 19:24 ` Borislav Petkov
2023-08-16 19:30 ` Nathan Chancellor
2023-08-16 19:42 ` Borislav Petkov
2023-08-16 19:57 ` Borislav Petkov
2023-08-16 21:20 ` tip-bot2 for Peter Zijlstra
2023-08-14 11:44 ` [PATCH v2 06/11] x86/cpu: Rename original retbleed methods Peter Zijlstra
2023-08-14 19:41 ` Josh Poimboeuf
2023-08-16 7:55 ` [tip: x86/urgent] " tip-bot2 for Peter Zijlstra
2023-08-16 21:20 ` tip-bot2 for Peter Zijlstra
2023-08-14 11:44 ` [PATCH v2 07/11] x86/cpu: Rename srso_(.*)_alias to srso_alias_\1 Peter Zijlstra
2023-08-16 7:55 ` [tip: x86/urgent] " tip-bot2 for Peter Zijlstra
2023-08-16 21:20 ` tip-bot2 for Peter Zijlstra
2023-08-14 11:44 ` [PATCH v2 08/11] x86/cpu: Cleanup the untrain mess Peter Zijlstra
2023-08-16 7:55 ` [tip: x86/urgent] " tip-bot2 for Peter Zijlstra
2023-08-16 21:20 ` tip-bot2 for Peter Zijlstra
2023-08-14 11:44 ` [PATCH v2 09/11] x86/cpu/kvm: Provide UNTRAIN_RET_VM Peter Zijlstra
2023-08-16 7:55 ` [tip: x86/urgent] " tip-bot2 for Peter Zijlstra
2023-08-16 21:20 ` tip-bot2 for Peter Zijlstra
2023-08-14 11:44 ` [PATCH v2 10/11] x86/alternatives: Simplify ALTERNATIVE_n() Peter Zijlstra
2023-08-15 20:49 ` Nikolay Borisov
2023-08-15 22:44 ` Peter Zijlstra
2023-09-07 8:31 ` Borislav Petkov
2023-09-07 11:09 ` Peter Zijlstra
2023-09-07 11:11 ` Peter Zijlstra
2023-09-07 11:16 ` Peter Zijlstra
2023-09-07 15:06 ` Borislav Petkov
2023-09-07 15:30 ` Borislav Petkov
2023-09-09 7:50 ` Borislav Petkov
2023-09-09 9:25 ` Peter Zijlstra
2023-09-09 9:42 ` Peter Zijlstra
2023-09-10 14:42 ` Borislav Petkov
2023-09-12 9:27 ` Peter Zijlstra [this message]
2023-09-12 9:44 ` Peter Zijlstra
2023-09-13 4:37 ` Borislav Petkov
2023-09-13 8:46 ` Peter Zijlstra
2023-09-13 14:38 ` Borislav Petkov
2023-09-13 16:14 ` Peter Zijlstra
2023-09-15 7:46 ` Peter Zijlstra
2023-09-15 7:51 ` Peter Zijlstra
2023-09-15 12:05 ` Borislav Petkov
2023-09-13 4:24 ` Borislav Petkov
2023-08-14 11:44 ` [PATCH v2 11/11] x86/cpu: Use fancy alternatives to get rid of entry_untrain_ret() Peter Zijlstra
2023-08-14 16:44 ` [PATCH v2 00/11] Fix up SRSO stuff Borislav Petkov
2023-08-14 19:51 ` Josh Poimboeuf
2023-08-14 19:57 ` Borislav Petkov
2023-08-14 20:01 ` Josh Poimboeuf
2023-08-14 20:09 ` Borislav Petkov
2023-08-15 14:26 ` [PATCH] x86/srso: Explain the untraining sequences a bit more Borislav Petkov
2023-08-15 15:41 ` Nikolay Borisov
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