On 6/17/2019 11:50 PM, Radim Krčmář wrote:
2019-06-17 14:31+0800, Xiaoyao Li:
On 6/17/2019 11:32 AM, Xiaoyao Li wrote:
On 6/16/2019 5:55 PM, Tao Xu wrote:
+ if (vmx->msr_ia32_umwait_control != host_umwait_control)
+ add_atomic_switch_msr(vmx, MSR_IA32_UMWAIT_CONTROL,
+ vmx->msr_ia32_umwait_control,
+ host_umwait_control, false);
The bit 1 is reserved, at least, we need to do below to ensure not
modifying the reserved bit:
guest_val = (vmx->msr_ia32_umwait_control & ~BIT_ULL(1)) |
(host_val & BIT_ULL(1))
I find a better solution to ensure reserved bit 1 not being modified in
vmx_set_msr() as below:
if((data ^ umwait_control_cached) & BIT_ULL(1))
return 1;
We could just be checking
if (data & BIT_ULL(1))
because the guest cannot change its visible reserved value and KVM
currently initializes the value to 0.
The arch/x86/kernel/cpu/umwait.c series assumes that the reserved bit
is 0 (hopefully deliberately) and I would do the same in KVM as it
simplifies the logic. (We don't have to even think about migrations
between machines with a different reserved value and making it play
nicely with possible future implementations of that bit.)
Got it, thanks.
Thanks.
