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    SubjectRe: [PATCH Part2 RFC v4 39/40] KVM: SVM: Use a VMSA physical address variable for populating VMCB
    On Wed, Jul 07, 2021, Brijesh Singh wrote:
    > From: Tom Lendacky <thomas.lendacky@amd.com>
    >
    > In preparation to support SEV-SNP AP Creation, use a variable that holds
    > the VMSA physical address rather than converting the virtual address.
    > This will allow SEV-SNP AP Creation to set the new physical address that
    > will be used should the vCPU reset path be taken.

    I'm pretty sure adding vmsa_pa is unnecessary. The next patch sets svm->vmsa_pa
    and vmcb->control.vmsa_pa as a pair. And for the existing code, my proposed
    patch to emulate INIT on shutdown would eliminate the one path that zeros the
    VMCB[1]. That series patch also drops the init_vmcb() in svm_create_vcpu()[2].

    Assuming there are no VMCB shenanigans I'm missing, sev_es_init_vmcb() can do

    if (!init_event)
    svm->vmcb->control.vmsa_pa = __pa(svm->vmsa);

    And while I'm thinking of it, the next patch should ideally free svm->vmsa when
    the the guest configures a new VMSA for the vCPU.

    [1] https://lkml.kernel.org/r/20210713163324.627647-45-seanjc@google.com
    [2] https://lkml.kernel.org/r/20210713163324.627647-10-seanjc@google.com

    > Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
    > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
    > ---
    > arch/x86/kvm/svm/sev.c | 5 ++---
    > arch/x86/kvm/svm/svm.c | 9 ++++++++-
    > arch/x86/kvm/svm/svm.h | 1 +
    > 3 files changed, 11 insertions(+), 4 deletions(-)
    >
    > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
    > index 4cb4c1d7e444..d8ad6dd58c87 100644
    > --- a/arch/x86/kvm/svm/sev.c
    > +++ b/arch/x86/kvm/svm/sev.c
    > @@ -3553,10 +3553,9 @@ void sev_es_init_vmcb(struct vcpu_svm *svm)
    >
    > /*
    > * An SEV-ES guest requires a VMSA area that is a separate from the
    > - * VMCB page. Do not include the encryption mask on the VMSA physical
    > - * address since hardware will access it using the guest key.
    > + * VMCB page.
    > */
    > - svm->vmcb->control.vmsa_pa = __pa(svm->vmsa);
    > + svm->vmcb->control.vmsa_pa = svm->vmsa_pa;
    >
    > /* Can't intercept CR register access, HV can't modify CR registers */
    > svm_clr_intercept(svm, INTERCEPT_CR0_READ);
    > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
    > index 32e35d396508..74bc635c9608 100644
    > --- a/arch/x86/kvm/svm/svm.c
    > +++ b/arch/x86/kvm/svm/svm.c
    > @@ -1379,9 +1379,16 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
    > svm->vmcb01.ptr = page_address(vmcb01_page);
    > svm->vmcb01.pa = __sme_set(page_to_pfn(vmcb01_page) << PAGE_SHIFT);
    >
    > - if (vmsa_page)
    > + if (vmsa_page) {
    > svm->vmsa = page_address(vmsa_page);
    >
    > + /*
    > + * Do not include the encryption mask on the VMSA physical
    > + * address since hardware will access it using the guest key.
    > + */
    > + svm->vmsa_pa = __pa(svm->vmsa);
    > + }
    > +
    > svm->guest_state_loaded = false;
    >
    > svm_switch_vmcb(svm, &svm->vmcb01);
    > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
    > index 9fcfc0a51737..285d9b97b4d2 100644
    > --- a/arch/x86/kvm/svm/svm.h
    > +++ b/arch/x86/kvm/svm/svm.h
    > @@ -177,6 +177,7 @@ struct vcpu_svm {
    >
    > /* SEV-ES support */
    > struct sev_es_save_area *vmsa;
    > + hpa_t vmsa_pa;
    > struct ghcb *ghcb;
    > struct kvm_host_map ghcb_map;
    > bool received_first_sipi;
    > --
    > 2.17.1
    >

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