Messages in this thread | | | Date | Tue, 3 Nov 2020 14:27:18 +0800 | From | Shuo A Liu <> | Subject | Re: [PATCH v5 03/17] x86/acrn: Introduce an API to check if a VM is privileged |
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Hi Boris,
On Mon 2.Nov'20 at 15:37:07 +0100, Borislav Petkov wrote: >On Mon, Oct 19, 2020 at 02:17:49PM +0800, shuo.a.liu@intel.com wrote: >> +bool acrn_is_privileged_vm(void) >> +{ >> + return cpuid_eax(acrn_cpuid_base() | ACRN_CPUID_FEATURES) & >> + ACRN_FEATURE_PRIVILEGED_VM; > >I asked in the previous review why that acrn_cpuid_base() is used here, >you said that the base might vary. Looking at hypervisor_cpuid_base(), >it searches in the range [0x40000000, 0x40010000] with an 0x100 offset. > >So you're saying that ACRN_CPUID_FEATURES is the first leaf beyond the >base. Close?
Yes.
> >If so, why isn't the code doing this? > > return cpuid_eax(acrn_cpuid_base() + 1)... > >and why doesn't it have a comment above it explaining that the base can >change and it needs to be discovered each time?
The code just followed KVM style (see kvm_arch_para_features()). I can change to use cpuid_eax(acrn_cpuid_base() + 1)... If you prefer to.
hypervisor_cpuid_base() implies the base is variable, no? We use this function to detect the base.
> >> +EXPORT_SYMBOL_GPL(acrn_is_privileged_vm); > >Also, that acrn_is_privileged_vm() silly helper is used only once and >I don't like the exported symbols pollution we're doing. So make that >function give you the eax of ACRN_CPUID_FEATURES and callers can do >their testing themselves.
OK. Then i will define acrn_cpuid_base() as a static inline function in asm/acrn.h for callers.
> >When it turns out that code patterns get repeated, you can then >aggregate stuff into a helper.
Got it. Thanks.
Thanks shuo
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