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