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

Daniel Verkamp
2019-01-31T17:14:39Z

Yes, please disregard this patch - I had this on my to-do list to
investigate and missed the stable update that fixed it already.

Thanks,
-- Daniel

On Wed, Jan 30, 2019 at 11:18 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> 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