From: David Laight <David.Laight@ACULAB.COM>
To: "'Andrew.Cooper3@citrix.com'" <Andrew.Cooper3@citrix.com>,
Peter Zijlstra <peterz@infradead.org>,
"x86@kernel.org" <x86@kernel.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"mhiramat@kernel.org" <mhiramat@kernel.org>,
"kirill.shutemov@linux.intel.com"
<kirill.shutemov@linux.intel.com>,
"jpoimboe@redhat.com" <jpoimboe@redhat.com>
Subject: RE: [PATCH v3 3/4] x86/alternative: Rewrite optimize_nops() some
Date: Wed, 8 Feb 2023 23:04:24 +0000 [thread overview]
Message-ID: <c76df3cb3c8944e98baad3406a522bad@AcuMS.aculab.com> (raw)
In-Reply-To: <f0b54521-26cf-ed38-d805-3a8eef3b3103@citrix.com>
From: Andrew.Cooper3@citrix.com
> Sent: 08 February 2023 19:52
...
> Unconditional jmps cost branch prediction these days, and won't be
> successfully predicted until taken.
That is sad :-(
Don't they also use the BTB for the target address?
So even if predicted taken the cpu can speculate from
the wrong address??
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2023-02-08 23:04 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-08 17:10 [PATCH v3 0/4] x86: Fully relocatable alternatives and some NOPs Peter Zijlstra
2023-02-08 17:10 ` [PATCH v3 1/4] x86/alternative: Make debug-alternative selective Peter Zijlstra
2023-02-14 11:48 ` Borislav Petkov
2023-05-13 13:03 ` [tip: x86/alternatives] " tip-bot2 for Peter Zijlstra
2023-02-08 17:10 ` [PATCH v3 2/4] x86/alternative: Support relocations in alternatives Peter Zijlstra
2023-02-17 20:28 ` Borislav Petkov
2023-02-17 22:21 ` Borislav Petkov
2023-05-13 13:03 ` [tip: x86/alternatives] " tip-bot2 for Peter Zijlstra
2023-02-08 17:10 ` [PATCH v3 3/4] x86/alternative: Rewrite optimize_nops() some Peter Zijlstra
2023-02-08 19:52 ` Andrew.Cooper3
2023-02-08 20:29 ` Peter Zijlstra
2023-02-08 20:36 ` Peter Zijlstra
2023-02-08 20:44 ` Peter Zijlstra
2023-02-08 20:45 ` Peter Zijlstra
2023-02-08 21:01 ` Peter Zijlstra
2023-02-08 21:08 ` Peter Zijlstra
2023-02-08 21:21 ` Peter Zijlstra
2023-02-09 1:11 ` Andrew.Cooper3
2023-02-09 22:27 ` David Laight
2023-02-09 1:33 ` Andrew.Cooper3
2023-02-08 23:04 ` David Laight [this message]
2023-05-13 13:03 ` [tip: x86/alternatives] " tip-bot2 for Peter Zijlstra
2023-02-27 10:49 ` [PATCH] x86/lib/memmove: Decouple ERMS from FSRM Borislav Petkov
2023-04-27 9:22 ` [PATCH TEST] " Yahu Gao
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