From: Borislav Petkov <bp@alien8.de>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Ashok Raj <ashok.raj@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>,
Ingo Molnar <mingo@kernel.org>, Tony Luck <tony.luck@intel.com>,
Alison Schofield <alison.schofield@intel.com>,
Reinette Chatre <reinette.chatre@intel.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Stefan Talpalaru <stefantalpalaru@yahoo.com>,
David Woodhouse <dwmw2@infradead.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Jonathan Corbet <corbet@lwn.net>,
"Rafael J . Wysocki" <rafael@kernel.org>,
Peter Zilstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
Andrew Cooper <Andrew.Cooper3@citrix.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Martin Pohlack <mpohlack@amazon.de>
Subject: Re: [Patch v3 Part2 4/9] x86/microcode: Do not call apply_microcode() on sibling threads
Date: Wed, 1 Feb 2023 23:40:58 +0100 [thread overview]
Message-ID: <Y9rqeqMjDOYJKmLZ@zn.tnic> (raw)
In-Reply-To: <bfd85699-4b7a-c606-266a-cea7ff336950@intel.com>
On Wed, Feb 01, 2023 at 02:21:18PM -0800, Dave Hansen wrote:
> That works great, unless T0 experiences an error. In that case, T0 will
> jump out of __reload_late() after failing to do the update. T1 will
> come bumbling along after it and will enter ->apply_microcode(),
> blissfully unaware of T0's failure. T1 will assume that it is supposed
> to do T0's job, noting "rev < mc->hdr.rev". T1 will write the MSR while
> T0 is off doing god knows what.
>
> T1 should not even be attempting to do ->apply_microcode() because T0 is
> not quiescent.
Yah, thanks for explaining properly.
So, if T0 fails, then we will say that it failed. The ->apply_microcode()
call on T1 was never meant to apply any microcode - just to update the
cached data.
Now, if T0 fails, then it doesn't matter what T1 does - you have a
bigger problem:
A subset of the cores is running with new microcode while other subset
with the old one. Now this is a shit situation I don't want to be in.
And I don't have a good way out of it.
Revert to the old patch? Maybe...
Retry to application on all again with the hope that it works this time?
What if some core touches a MSR being added with the new microcode
patch?
Late loading is a big PITA. As we've been preaching for a while now.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2023-02-01 22:41 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-30 21:39 [Patch v3 Part2 0/9] x86/microcode: Declare microcode safe for late loading Ashok Raj
2023-01-30 21:39 ` [Patch v3 Part2 1/9] x86/microcode: Taint kernel only if microcode loading was successful Ashok Raj
2023-01-31 11:50 ` Borislav Petkov
2023-01-31 16:51 ` Ashok Raj
2023-01-31 20:20 ` Borislav Petkov
2023-01-31 22:54 ` Ashok Raj
2023-02-01 12:44 ` Borislav Petkov
2023-02-01 15:42 ` Ashok Raj
2023-02-01 21:47 ` Ashok Raj
2023-02-01 22:06 ` Borislav Petkov
2023-02-01 22:19 ` Ashok Raj
2023-02-01 22:26 ` Borislav Petkov
2023-01-31 12:17 ` Li, Aubrey
2023-01-31 15:32 ` Ashok Raj
2023-01-30 21:39 ` [Patch v3 Part2 2/9] x86/microcode: Report invalid writes to reload sysfs file Ashok Raj
2023-01-31 15:57 ` [tip: x86/microcode] x86/microcode: Allow only "1" as a late reload trigger value tip-bot2 for Ashok Raj
2023-01-30 21:39 ` [Patch v3 Part2 3/9] x86/microcode/intel: Fix collect_cpu_info() to reflect current microcode Ashok Raj
2023-01-31 16:48 ` Borislav Petkov
2023-01-31 17:34 ` Luck, Tony
2023-01-31 17:41 ` Ashok Raj
2023-01-31 20:40 ` Borislav Petkov
2023-01-31 20:49 ` Luck, Tony
2023-01-31 21:08 ` Borislav Petkov
2023-01-31 22:32 ` Ashok Raj
2023-01-31 22:43 ` Luck, Tony
2023-02-01 12:53 ` Borislav Petkov
2023-02-01 15:13 ` Ashok Raj
2023-02-01 15:25 ` Borislav Petkov
2023-02-01 16:15 ` Luck, Tony
2023-02-01 19:13 ` Dave Hansen
2023-02-01 19:32 ` Ashok Raj
2023-01-30 21:39 ` [Patch v3 Part2 4/9] x86/microcode: Do not call apply_microcode() on sibling threads Ashok Raj
2023-02-01 22:21 ` Dave Hansen
2023-02-01 22:40 ` Borislav Petkov [this message]
2023-02-02 2:51 ` Ashok Raj
2023-02-02 9:40 ` Borislav Petkov
2023-02-02 16:34 ` Ashok Raj
2023-01-30 21:39 ` [Patch v3 Part2 5/9] x86/microcode: Move late load warning to the same function that taints kernel Ashok Raj
2023-01-30 21:39 ` [Patch v3 Part2 6/9] x86/microcode/intel: Add minimum required revision to microcode header Ashok Raj
2023-01-30 21:39 ` [Patch v3 Part2 7/9] x86/microcode: Add a generic mechanism to declare support for minrev Ashok Raj
2023-01-30 21:39 ` [Patch v3 Part2 8/9] x86/microcode/intel: Drop wbinvd() from microcode loading Ashok Raj
2023-01-30 21:39 ` [Patch v3 Part2 9/9] x86/microcode: Provide an option to override minrev enforcement Ashok Raj
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