Messages in this thread | | | Subject | Re: [PATCH v3 2/2] KVM: VMX: untangle VMXON revision_id setting when using eVMCS | From | Krish Sadhukhan <> | Date | Fri, 6 Mar 2020 17:34:10 -0800 |
| |
On 3/6/20 4:28 PM, Sean Christopherson wrote: > On Fri, Mar 06, 2020 at 03:57:25PM -0800, Krish Sadhukhan wrote: >> On 3/6/20 3:07 PM, Sean Christopherson wrote: >>> On Fri, Mar 06, 2020 at 02:20:13PM -0800, Krish Sadhukhan wrote: >>>>> @@ -2599,7 +2607,7 @@ void free_loaded_vmcs(struct loaded_vmcs *loaded_vmcs) >>>>> int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs) >>>>> { >>>>> - loaded_vmcs->vmcs = alloc_vmcs(false); >>>>> + loaded_vmcs->vmcs = alloc_vmcs(VMCS_REGION); >>>>> if (!loaded_vmcs->vmcs) >>>>> return -ENOMEM; >>>>> @@ -2652,25 +2660,13 @@ static __init int alloc_vmxon_regions(void) >>>>> for_each_possible_cpu(cpu) { >>>>> struct vmcs *vmcs; >>>>> - vmcs = alloc_vmcs_cpu(false, cpu, GFP_KERNEL); >>>>> + /* The VMXON region is really just a special type of VMCS. */ >>>> Not sure if this is the right way to correlate the two. >>>> >>>> AFAIU, the SDM calls VMXON region as a memory area that holds the VMCS data >>>> structure and it calls VMCS the data structure that is used by software to >>>> switch between VMX root-mode and not-root-mode. So VMXON is a memory area >>>> whereas VMCS is the structure of the data that resides in that memory area. >>>> >>>> So if we follow this interpretation, your enum should rather look like, >>>> >>>> enum vmcs_type { >>>> + VMCS, >>>> + EVMCS, >>>> + SHADOW_VMCS >>> No (to the EVMCS suggestion), because this allocation needs to happen for >>> !eVMCS. The SDM never explictly calls the VMXON region a VMCS, but it's >>> just being coy. E.g. VMCLEAR doesn't fail if you point it at random >>> memory, but point it at the VMXON region and it yells. >>> >>> We could call it VMXON_VMCS if that helps. >> Are you saying, >> >> + enum vmcs_type { >> + VMXON_REGION, >> + VMXON_VMCS, >> + SHADOW_VMCS_REGION, >> +}; >> >> ? >> >> In that case, "VMXON_REGION" and "VMXON_VMCS" are no different according to >> your explanation. > enum vmcs_type { > VMXON_VMCS, > VMCS, > SHADOW_VMCS, > };
It looks reasonable.
> > alloc_vmcs_cpu() does more than just allocate the memory, it also > initializes the data structure, e.g. "allocate and initalize a VMXON VMCS", > >>> The SDM does call the memory >>> allocation for regular VMCSes a "VMCS region": >>> >>> A logical processor associates a region in memory with each VMCS. This >>> region is called the VMCS region. >>> >>> I don't think I've ever heard anyone differentiate that two though, i.e. >>> VMCS is used colloquially to mean both the data structure itself and the >>> memory region containing the data structure. >>> >>>>> + vmcs = alloc_vmcs_cpu(VMXON_REGION, cpu, GFP_KERNEL); >>>>> if (!vmcs) { >>>>> free_vmxon_regions(); >>>>> return -ENOMEM; >>>>> } >>>>> - /* >>>>> - * When eVMCS is enabled, alloc_vmcs_cpu() sets >>>>> - * vmcs->revision_id to KVM_EVMCS_VERSION instead of >>>>> - * revision_id reported by MSR_IA32_VMX_BASIC. >>>>> - * >>>>> - * However, even though not explicitly documented by >>>>> - * TLFS, VMXArea passed as VMXON argument should >>>>> - * still be marked with revision_id reported by >>>>> - * physical CPU. >>>>> - */ >>>>> - if (static_branch_unlikely(&enable_evmcs)) >>>>> - vmcs->hdr.revision_id = vmcs_config.revision_id; >>>>> - >>>>> per_cpu(vmxarea, cpu) = vmcs; >>>>> } >>>>> return 0; >>>>> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h >>>>> index e64da06c7009..a5eb92638ac2 100644 >>>>> --- a/arch/x86/kvm/vmx/vmx.h >>>>> +++ b/arch/x86/kvm/vmx/vmx.h >>>>> @@ -489,16 +489,22 @@ static inline struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu) >>>>> return &(to_vmx(vcpu)->pi_desc); >>>>> } >>>>> -struct vmcs *alloc_vmcs_cpu(bool shadow, int cpu, gfp_t flags); >>>>> +enum vmcs_type { >>>>> + VMXON_REGION, >>>>> + VMCS_REGION, >>>>> + SHADOW_VMCS_REGION, >>>>> +}; >>>>> + >>>>> +struct vmcs *alloc_vmcs_cpu(enum vmcs_type type, int cpu, gfp_t flags); >>>>> void free_vmcs(struct vmcs *vmcs); >>>>> int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs); >>>>> void free_loaded_vmcs(struct loaded_vmcs *loaded_vmcs); >>>>> void loaded_vmcs_init(struct loaded_vmcs *loaded_vmcs); >>>>> void loaded_vmcs_clear(struct loaded_vmcs *loaded_vmcs); >>>>> -static inline struct vmcs *alloc_vmcs(bool shadow) >>>>> +static inline struct vmcs *alloc_vmcs(enum vmcs_type type) >>>>> { >>>>> - return alloc_vmcs_cpu(shadow, raw_smp_processor_id(), >>>>> + return alloc_vmcs_cpu(type, raw_smp_processor_id(), >>>>> GFP_KERNEL_ACCOUNT); >>>>> }
| |