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 2/8] x86, microcode, intel: don't update each HT core twice
Date: Tue, 28 Oct 2014 18:31:09 +0100 [thread overview]
Message-ID: <20141028173109.GB10873@pd.tnic> (raw)
In-Reply-To: <20141020182427.GB19306@khazad-dum.debian.net>
On Mon, Oct 20, 2014 at 04:24:27PM -0200, Henrique de Moraes Holschuh wrote:
> Over time, grepping for that information on reports and logs all over the
> net has helped me a great deal.
Helped you how, for what? I still am searching for a justification to
bother the user with the fact that her microcode just got upgraded. I
mean, she can simply do:
$ grep microcode /proc/cpuinfo | head -1
microcode : 0x6000822
if needed.
Now, the error cases where the upgrade fails for some unexpected reason
is what we want to know.
> I really miss the full microcode ID information in /proc/cpuinfo, in fact.
Full ID, you mean all fields of struct cpu_signature on Intel?
If so,
->sig - CPUID_EAX(1) which is in /proc/cpuinfo
->pf - processor flags in MSR_0x17[52:50] - I guess you can read that
out with rdmsr 0x17. Why do we need to know that one except maybe to
verify why a patch doesn't get accepted by the loader?
-> rev - that's in MSR_IA32_UCODE_REV
I'm not really sure we absolutely need those except for debugging. Thus
the pr_debug() suggestion from my side.
> MSR 79H writes are on a class of their own as far as "expensive" goes... On
> a modern i3/i5/i7, it will take approximately one million cycles to complete
> (the larger the microcode update, the longer it takes).
>
> I don't think people usually associate MSR write with "takes one million
> cycles to complete"...
So? You don't do microcode updates all the time - it is done once during
boot and when cores come back online.
> This is old code, I guess it predates wrmsrl()...
>
> Should I replace the old split version with wrmsrl() in this patch, or as a
> separate patch?
Yes please. And then add to the commit message something of the sorts
"While at it, ..."
Thanks.
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
--
next prev parent reply other threads:[~2014-10-28 17:31 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 [this message]
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
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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