From: Dave Hansen <dave.hansen@intel.com>
To: Matthias Welwarsky <matthias.welwarsky@sysgo.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, x86-ml <x86@kernel.org>
Subject: Re: x86, possible bug in __memmove() alternatives patching
Date: Tue, 29 Mar 2022 15:33:17 -0700 [thread overview]
Message-ID: <066bbff7-d2fe-44d3-0245-ccbcb5990257@intel.com> (raw)
In-Reply-To: <3346653.QJadu78ljV@linux-3513>
On 3/26/22 04:39, Matthias Welwarsky wrote:
>
>> But, we do try to make the kernel work even the face of funky
>> hypervisors that do things that never occur on real hardware. If a nice
>> patch to fix this up showed up, I'd definitely take a look.
> The question is whether a sequence like this could be relevant:
>
> 0) CPU announces feature FSRM through cpuid
> 1) BIOS/firmware disables fast string ops through IA32_MISC_ENABLE before
> loading kernel (for whatever reason)
> 2) Kernel populates features from cpuid
> 3) Kernel clears ERMS based on IA32_MISC_ENABLE
> 4) "alternatives" patching destroys __memmove()
Hi Matthias,
What does "destroys __memmove()" mean in practice? What's the end-user
visible effect of this? Do they see a crash or just crummy performance?
next prev parent reply other threads:[~2022-03-29 22:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-25 8:51 x86, possible bug in __memmove() alternatives patching Matthias Welwarsky
2022-03-25 22:07 ` Borislav Petkov
2022-03-26 4:45 ` Dave Hansen
2022-03-26 8:27 ` Borislav Petkov
2022-03-29 22:34 ` Dave Hansen
2022-03-26 11:39 ` Matthias Welwarsky
2022-03-29 22:33 ` Dave Hansen [this message]
2022-03-30 13:56 ` Matthias Welwarsky
2022-03-30 14:44 ` Dave Hansen
2022-03-30 14:54 ` Borislav Petkov
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