Re: [PATCH v2 for-4.14-stable] x86,kvm: remove extra kvm_{get,put}_guest_fpu

Greg KH
2019-01-31T07:18:20Z

On Wed, Jan 30, 2019 at 02:29:26PM -0800, Daniel Verkamp wrote:
> Commit 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out
> to vcpu_run") applied a patch from upstream, but it appears that it
> wasn't backported correctly to 4.14. The extra out_fpu label and
> kvm_put_guest_fpu() added in kvm_arch_vcpu_ioctl_run() result in calling
> kvm_put_guest_fpu() twice in a row, corrupting guest state.
> Additionally, a duplicate kvm_load_guest_fpu() is added in the middle of
> the function.
>
> Fixes: 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run")
> Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
> ---
>
> v2: removed additional redundant kvm_load_guest_fpu()
>
> I'm unsure if this is the right way to send this fix - there is no
> corresponding mainline commit to reference, since the code there is
> already correct, and the problem was introduced in the cherry-picked
> stable backport. Please let me know if there's a different process for
> fixes to stable-only issues.

This should now be fixed with 9485d5d2318b ("KVM: x86: Fix a 4.14
backport regression related to userspace/guest FPU") in the 4.14.97
release that just happened, right?

thanks,

greg k-h