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

[Thibault Ferrante]

Acked-by: Thibault Ferrante <thibault.ferrante at canonical.com>


On 06-09-2024 19:37, Bethany Jamison wrote:
> BugLink: https://bugs.launchpad.net/bugs/2077321
Why does the bug is written as Confirmed for oracular even if the fix commit is already there as it was merged in 6.10
> 
> 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(+)
> 


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Thibault