On 12/10/21 02:00, Thomas Gleixner wrote:
- if (boot_cpu_has(X86_FEATURE_XSAVE)) {
- memset(guest_xsave, 0, sizeof(struct kvm_xsave));
- fill_xsave((u8 *) guest_xsave->region, vcpu);
- } else {
- memcpy(guest_xsave->region,
- &vcpu->arch.guest_fpu->state.fxsave,
- sizeof(struct fxregs_state));
- *(u64 *)&guest_xsave->region[XSAVE_HDR_OFFSET / sizeof(u32)] =
- XFEATURE_MASK_FPSSE;
- }
After the patch, this final assignment is not done in the else case:
+
+ if (cpu_feature_enabled(X86_FEATURE_XSAVE)) {
+ __copy_xstate_to_uabi_buf(mb, &kstate->xsave, pkru,
+ XSTATE_COPY_XSAVE);
+ } else {
+ memcpy(&ustate->fxsave, &kstate->fxsave, sizeof(ustate->fxsave));
+ }
+}
This leaves the xstate_bv set to 0 instead of XFEATURE_MASK_FPSSE.
Resuming a VM then fails if you save on a non-XSAVE machine and restore
it on an XSAVE machine.
The memset(guest_xsave, 0, sizeof(struct kvm_xsave)) also is not
reproduced, you can make it unconditional for simplicity; this is not a
fast path.
Paolo
