Re: [PATCH v2] hvf: guard xgetbv call.

[Hill Ma]

On Sun, Jan 10, 2021 at 8:38 PM Roman Bolshakov <r.bolshakov@yadro.com> wrote:
> I'm not sure if eax should be modified with mask because the mask has no
> value per se. I.e. eax &= supp_xcr0 from below should be placed inside
> the if. It'd express clearly that eax is not modified unless xgetbv is
> supported.

Like this?

-            uint64_t host_xcr0 = xgetbv(0);
-            uint64_t supp_xcr0 = host_xcr0 & (XSTATE_FP_MASK |
XSTATE_SSE_MASK |
+            uint64_t host_xcr0;
+            if (xgetbv(ecx, 0, &host_xcr0)) {
+                uint64_t supp_xcr0 = host_xcr0 & (XSTATE_FP_MASK |
XSTATE_SSE_MASK |
                                   XSTATE_YMM_MASK | XSTATE_BNDREGS_MASK |
                                   XSTATE_BNDCSR_MASK | XSTATE_OPMASK_MASK |
                                   XSTATE_ZMM_Hi256_MASK |
XSTATE_Hi16_ZMM_MASK);
-            eax &= supp_xcr0;
+                eax &= supp_xcr0;
+            }