Re: [PATCH] KVM: vmx: Fix the broken usage of vmx_xsaves_supported

From: Paolo Bonzini
Date: Thu Jun 20 2019 - 04:22:47 EST

On 20/06/19 08:46, Xiaoyao Li wrote:
>> It depends on whether or not processors support the 1-setting instead
>> of âenable XSAVES/XRSTORSâ is 1 in VM-exection control field. Anyway,
> Yes, whether this field exist or not depends on whether processors
> support the 1-setting.
> But if "enable XSAVES/XRSTORS" is clear to 0, XSS_EXIT_BITMAP doesn't
> work. I think in this case, there is no need to set this vmcs field?

vmx->secondary_exec_control can change; you are making the code more
complex by relying on the value of the field at the point of vmx_vcpu_setup.

I do _think_ your version is incorrect, because at this point CPUID has
not been initialized yet and therefore
vmx_compute_secondary_exec_control has not set SECONDARY_EXEC_XSAVES.
However I may be wrong because I didn't review the code very closely:
the old code is obvious and so there is no point in changing it.