lkml.org 
[lkml]   [2020]   [Mar]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: [PATCH v3 2/2] KVM: VMX: untangle VMXON revision_id setting when using eVMCS
    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,
    };

    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);
    > >>> }

    \
     
     \ /
      Last update: 2020-03-07 01:29    [W:4.746 / U:0.212 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site