From: Borislav Petkov <bp@alien8.de>
To: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: linux-kernel@vger.kernel.org, H Peter Anvin <hpa@zytor.com>
Subject: Re: [PATCH 6/8] x86, microcode, intel: use cpuid explicitly instead of sync_core
Date: Fri, 7 Nov 2014 18:56:45 +0100 [thread overview]
Message-ID: <20141107175645.GC5180@pd.tnic> (raw)
In-Reply-To: <1410197875-19252-7-git-send-email-hmh@hmh.eng.br>
On Mon, Sep 08, 2014 at 02:37:52PM -0300, Henrique de Moraes Holschuh wrote:
> The protocol to safely read MSR 8BH, described in the Intel SDM vol 3A,
> section 9.11.7.1, explicitly determines that cpuid with EAX=1 must be
> used between the wrmsr(0x8B, 0); and the rdmsr(0x8B).
>
> The microcode driver was abusing sync_core() to do this, probably
> because it predates by nearly a decade the current "asm volatile
> (:::"memory")" implementation of native_cpuid(), which is required for
> the Intel MSR 8BH access protocol.
Huh, what? Have you taken a look at sync_core() first?
> sync_core() semanthics are that of being a speculative execution
> barrier, and not "run cpuid with EAX=1".
Again, what?
Hmm, let's see:
static inline void sync_core(void)
{
...
asm volatile("cpuid"
: "=a" (tmp)
: "0" (1)
: "ebx", "ecx", "edx", "memory");
What is the problem again?
I'm sorry but I don't understand what you're trying to fix here...
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
--
next prev parent reply other threads:[~2014-11-07 17:56 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-08 17:37 [PATCH 0/8] x86, microcode, intel: fixes and enhancements Henrique de Moraes Holschuh
2014-09-08 17:37 ` [PATCH 1/8] x86, microcode, intel: forbid some incorrect metadata Henrique de Moraes Holschuh
2014-10-05 17:34 ` Borislav Petkov
2014-10-05 19:37 ` Henrique de Moraes Holschuh
2014-10-05 21:13 ` Borislav Petkov
2014-10-05 21:49 ` Henrique de Moraes Holschuh
2014-10-06 5:15 ` Borislav Petkov
2014-09-08 17:37 ` [PATCH 2/8] x86, microcode, intel: don't update each HT core twice Henrique de Moraes Holschuh
2014-10-20 13:32 ` Borislav Petkov
2014-10-20 18:24 ` Henrique de Moraes Holschuh
2014-10-28 17:31 ` Borislav Petkov
2014-10-31 18:43 ` Henrique de Moraes Holschuh
2014-11-01 11:06 ` Borislav Petkov
2014-11-01 19:20 ` Henrique de Moraes Holschuh
2014-11-04 15:53 ` Borislav Petkov
2014-09-08 17:37 ` [PATCH 3/8] x86, microcode, intel: clarify log messages Henrique de Moraes Holschuh
2014-10-20 13:52 ` Borislav Petkov
2014-10-21 14:13 ` Henrique de Moraes Holschuh
2014-10-29 9:54 ` Borislav Petkov
2014-10-31 20:08 ` Henrique de Moraes Holschuh
2014-11-07 17:37 ` Borislav Petkov
2014-09-08 17:37 ` [PATCH 4/8] x86, microcode, intel: add error logging to early update driver Henrique de Moraes Holschuh
2014-10-20 15:08 ` Borislav Petkov
2014-10-21 14:10 ` Henrique de Moraes Holschuh
2014-10-30 17:41 ` Borislav Petkov
2014-10-30 18:15 ` Joe Perches
2014-10-31 20:10 ` Henrique de Moraes Holschuh
2014-09-08 17:37 ` [PATCH 5/8] x86, microcode, intel: don't check extsig entry checksum Henrique de Moraes Holschuh
2014-10-30 20:25 ` Borislav Petkov
2014-10-31 17:14 ` Henrique de Moraes Holschuh
2014-11-07 17:49 ` Borislav Petkov
2014-09-08 17:37 ` [PATCH 6/8] x86, microcode, intel: use cpuid explicitly instead of sync_core Henrique de Moraes Holschuh
2014-11-07 17:56 ` Borislav Petkov [this message]
2014-11-07 18:40 ` Henrique de Moraes Holschuh
2014-11-07 19:48 ` Borislav Petkov
2014-09-08 17:37 ` [PATCH 7/8] x86, microcode, intel: guard against misaligned microcode data Henrique de Moraes Holschuh
2014-09-18 0:48 ` Henrique de Moraes Holschuh
2014-11-07 19:59 ` Borislav Petkov
2014-11-07 22:54 ` Henrique de Moraes Holschuh
2014-11-07 23:48 ` Borislav Petkov
2014-11-08 21:57 ` Henrique de Moraes Holschuh
2014-11-11 10:47 ` Borislav Petkov
2014-11-11 16:57 ` Henrique de Moraes Holschuh
2014-11-11 17:13 ` Borislav Petkov
2014-11-11 19:54 ` Henrique de Moraes Holschuh
2014-11-12 12:31 ` Borislav Petkov
2014-11-13 0:18 ` Henrique de Moraes Holschuh
2014-11-13 11:53 ` Borislav Petkov
2014-11-15 23:10 ` Henrique de Moraes Holschuh
2014-11-24 17:35 ` Borislav Petkov
2014-11-25 13:29 ` Henrique de Moraes Holschuh
2014-09-08 17:37 ` [PATCH 8/8] x86, microcode, intel: defend apply_microcode_intel with BUG_ON Henrique de Moraes Holschuh
2014-11-07 20:05 ` Borislav Petkov
2014-11-07 22:56 ` Henrique de Moraes Holschuh
2014-11-07 23:48 ` Borislav Petkov
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