ACK: [SRU][N,J][PATCH v3 0/1] disable XSAVES workaround

[Mehmet Basaran]

Acked-by: Mehmet Basaran <mehmet.basaran at canonical.com>

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Bethany Jamison <bethany.jamison at canonical.com> writes:

> BugLink: https://bugs.launchpad.net/bugs/2077321
>
> SRU Justification:
>
> [Impact]
>
> This patch fixes bug LP#2077321. An older commit (b056346) completely 
> disables XSAVES instruction on all AMD ZEN1/2 hardware to avoid a bug
> within that instruction (utilizes XSAVEC instruction instead). This 
> method of working around this issue is a bit too broad and causes an
> issue with migrating QEMU VMs from older kernels that use XSAVES to 
> newer kernels with XSAVES disabled. This patch implements a commit
> (29ba89f) to improve the workaround. It disables XSAVES only on 
> machines that lack a revised piece of microcode that addresses the
> XSAVES bug.
>
> [Fix]
>
> Above Commits:
> b056346 (x86/CPU/AMD: Disable XSAVES on AMD family 0x17) - https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/jammy/commit/?id=b0563468eeac88ebc70559d52a0b66efc37e4e9d
> 29ba89f (x86/CPU/AMD: Improve the erratum 1386 workaround) - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=29ba89f1895285f06c333546882e0c5ae9a6df23
>
> Commit 29ba89f was cleanly cherry-pick to Noble. I had to adjust the 
> context for Jammy because J was missing the definition for 'fix_erratum_1386', 
> but this should not affect the fix changes.
>
> [Test]
>  
> Compile tested
>
> [Where problems could occur]
>
> This fix affects those who use x86 processors, an issue with this fix
> would be visible to the user via issues migrating QEMU VMs from older 
> to newer kernels, or via XSAVEC being used instead of XSAVES in qualified
> machines.
>
> v2: adjusted to better match the stable patch format
>
> v3: submited v2 too soon, needed to add impact/fix/test/problems sections
>
> Borislav Petkov (AMD) (1):
>   x86/CPU/AMD: Improve the erratum 1386 workaround
>
>  arch/x86/include/asm/cpu_device_id.h |  8 ++++++++
>  arch/x86/kernel/cpu/amd.c            | 12 ++++++++++++
>  2 files changed, 20 insertions(+)
>
> -- 
> 2.34.1
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