lkml.org 
[lkml]   [2022]   [Aug]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH Part2 v6 39/49] KVM: SVM: Introduce ops for the post gfn map and unmap
    On Mon, Jun 20, 2022 at 4:12 PM Ashish Kalra <Ashish.Kalra@amd.com> wrote:
    >
    > From: Brijesh Singh <brijesh.singh@amd.com>
    >
    > When SEV-SNP is enabled in the guest VM, the guest memory pages can
    > either be a private or shared. A write from the hypervisor goes through
    > the RMP checks. If hardware sees that hypervisor is attempting to write
    > to a guest private page, then it triggers an RMP violation #PF.
    >
    > To avoid the RMP violation with GHCB pages, added new post_{map,unmap}_gfn
    > functions to verify if its safe to map GHCB pages. Uses a spinlock to
    > protect against the page state change for existing mapped pages.
    >
    > Need to add generic post_{map,unmap}_gfn() ops that can be used to verify
    > that its safe to map a given guest page in the hypervisor.
    >
    > This patch will need to be revisited later after consensus is reached on
    > how to manage guest private memory as probably UPM private memslots will
    > be able to handle this page state change more gracefully.
    >
    > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
    > Signed-off by: Ashish Kalra <ashish.kalra@amd.com>
    > ---
    > arch/x86/include/asm/kvm-x86-ops.h | 1 +
    > arch/x86/include/asm/kvm_host.h | 3 ++
    > arch/x86/kvm/svm/sev.c | 48 ++++++++++++++++++++++++++++--
    > arch/x86/kvm/svm/svm.c | 3 ++
    > arch/x86/kvm/svm/svm.h | 11 +++++++
    > 5 files changed, 64 insertions(+), 2 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
    > index e0068e702692..2dd2bc0cf4c3 100644
    > --- a/arch/x86/include/asm/kvm-x86-ops.h
    > +++ b/arch/x86/include/asm/kvm-x86-ops.h
    > @@ -130,6 +130,7 @@ KVM_X86_OP(vcpu_deliver_sipi_vector)
    > KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons);
    > KVM_X86_OP(alloc_apic_backing_page)
    > KVM_X86_OP_OPTIONAL(rmp_page_level_adjust)
    > +KVM_X86_OP(update_protected_guest_state)
    >
    > #undef KVM_X86_OP
    > #undef KVM_X86_OP_OPTIONAL
    > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    > index 49b217dc8d7e..8abc0e724f5c 100644
    > --- a/arch/x86/include/asm/kvm_host.h
    > +++ b/arch/x86/include/asm/kvm_host.h
    > @@ -1522,7 +1522,10 @@ struct kvm_x86_ops {
    > unsigned long (*vcpu_get_apicv_inhibit_reasons)(struct kvm_vcpu *vcpu);
    >
    > void *(*alloc_apic_backing_page)(struct kvm_vcpu *vcpu);
    > +
    > void (*rmp_page_level_adjust)(struct kvm *kvm, kvm_pfn_t pfn, int *level);
    > +
    > + int (*update_protected_guest_state)(struct kvm_vcpu *vcpu);
    > };
    >
    > struct kvm_x86_nested_ops {
    > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
    > index cb2d1bbb862b..4ed90331bca0 100644
    > --- a/arch/x86/kvm/svm/sev.c
    > +++ b/arch/x86/kvm/svm/sev.c
    > @@ -341,6 +341,7 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
    > if (ret)
    > goto e_free;
    >
    > + spin_lock_init(&sev->psc_lock);
    > ret = sev_snp_init(&argp->error);
    > } else {
    > ret = sev_platform_init(&argp->error);
    > @@ -2828,19 +2829,28 @@ static inline int svm_map_ghcb(struct vcpu_svm *svm, struct kvm_host_map *map)
    > {
    > struct vmcb_control_area *control = &svm->vmcb->control;
    > u64 gfn = gpa_to_gfn(control->ghcb_gpa);
    > + struct kvm_vcpu *vcpu = &svm->vcpu;
    >
    > - if (kvm_vcpu_map(&svm->vcpu, gfn, map)) {
    > + if (kvm_vcpu_map(vcpu, gfn, map)) {
    > /* Unable to map GHCB from guest */
    > pr_err("error mapping GHCB GFN [%#llx] from guest\n", gfn);
    > return -EFAULT;
    > }
    >
    > + if (sev_post_map_gfn(vcpu->kvm, map->gfn, map->pfn)) {
    > + kvm_vcpu_unmap(vcpu, map, false);
    > + return -EBUSY;
    > + }
    > +
    > return 0;
    > }
    >
    > static inline void svm_unmap_ghcb(struct vcpu_svm *svm, struct kvm_host_map *map)
    > {
    > - kvm_vcpu_unmap(&svm->vcpu, map, true);
    > + struct kvm_vcpu *vcpu = &svm->vcpu;
    > +
    > + kvm_vcpu_unmap(vcpu, map, true);
    > + sev_post_unmap_gfn(vcpu->kvm, map->gfn, map->pfn);
    > }
    >
    > static void dump_ghcb(struct vcpu_svm *svm)
    > @@ -3383,6 +3393,8 @@ static int __snp_handle_page_state_change(struct kvm_vcpu *vcpu, enum psc_op op,
    > return PSC_UNDEF_ERR;
    > }
    >
    > + spin_lock(&sev->psc_lock);
    > +
    > write_lock(&kvm->mmu_lock);
    >
    > rc = kvm_mmu_get_tdp_walk(vcpu, gpa, &pfn, &npt_level);
    > @@ -3417,6 +3429,8 @@ static int __snp_handle_page_state_change(struct kvm_vcpu *vcpu, enum psc_op op,
    >
    > write_unlock(&kvm->mmu_lock);
    >
    > + spin_unlock(&sev->psc_lock);

    There is a corner case where the psc_lock is not released. If
    kvm_mmu_get_tdp_walk fails, the lock will be kept and will cause soft
    lockup.

    > +
    > if (rc) {
    > pr_err_ratelimited("Error op %d gpa %llx pfn %llx level %d rc %d\n",
    > op, gpa, pfn, level, rc);
    > @@ -3965,3 +3979,33 @@ void sev_rmp_page_level_adjust(struct kvm *kvm, kvm_pfn_t pfn, int *level)
    > /* Adjust the level to keep the NPT and RMP in sync */
    > *level = min_t(size_t, *level, rmp_level);
    > }
    > +
    > +int sev_post_map_gfn(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn)
    > +{
    > + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
    > + int level;
    > +
    > + if (!sev_snp_guest(kvm))
    > + return 0;
    > +
    > + spin_lock(&sev->psc_lock);
    > +
    > + /* If pfn is not added as private then fail */
    > + if (snp_lookup_rmpentry(pfn, &level) == 1) {
    > + spin_unlock(&sev->psc_lock);
    > + pr_err_ratelimited("failed to map private gfn 0x%llx pfn 0x%llx\n", gfn, pfn);
    > + return -EBUSY;
    > + }
    > +
    > + return 0;
    > +}
    > +
    > +void sev_post_unmap_gfn(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn)
    > +{
    > + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
    > +
    > + if (!sev_snp_guest(kvm))
    > + return;
    > +
    > + spin_unlock(&sev->psc_lock);
    > +}
    > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
    > index b24e0171cbf2..1c8e035ba011 100644
    > --- a/arch/x86/kvm/svm/svm.c
    > +++ b/arch/x86/kvm/svm/svm.c
    > @@ -4734,7 +4734,10 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
    > .vcpu_get_apicv_inhibit_reasons = avic_vcpu_get_apicv_inhibit_reasons,
    >
    > .alloc_apic_backing_page = svm_alloc_apic_backing_page,
    > +
    > .rmp_page_level_adjust = sev_rmp_page_level_adjust,
    > +
    > + .update_protected_guest_state = sev_snp_update_protected_guest_state,
    > };
    >
    > /*
    > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
    > index 54ff56cb6125..3fd95193ed8d 100644
    > --- a/arch/x86/kvm/svm/svm.h
    > +++ b/arch/x86/kvm/svm/svm.h
    > @@ -79,19 +79,25 @@ struct kvm_sev_info {
    > bool active; /* SEV enabled guest */
    > bool es_active; /* SEV-ES enabled guest */
    > bool snp_active; /* SEV-SNP enabled guest */
    > +
    > unsigned int asid; /* ASID used for this guest */
    > unsigned int handle; /* SEV firmware handle */
    > int fd; /* SEV device fd */
    > +
    > unsigned long pages_locked; /* Number of pages locked */
    > struct list_head regions_list; /* List of registered regions */
    > +
    > u64 ap_jump_table; /* SEV-ES AP Jump Table address */
    > +
    > struct kvm *enc_context_owner; /* Owner of copied encryption context */
    > struct list_head mirror_vms; /* List of VMs mirroring */
    > struct list_head mirror_entry; /* Use as a list entry of mirrors */
    > struct misc_cg *misc_cg; /* For misc cgroup accounting */
    > atomic_t migration_in_progress;
    > +
    > u64 snp_init_flags;
    > void *snp_context; /* SNP guest context page */
    > + spinlock_t psc_lock;
    > };
    >
    > struct kvm_svm {
    > @@ -702,6 +708,11 @@ void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa);
    > void sev_es_unmap_ghcb(struct vcpu_svm *svm);
    > struct page *snp_safe_alloc_page(struct kvm_vcpu *vcpu);
    > void sev_rmp_page_level_adjust(struct kvm *kvm, kvm_pfn_t pfn, int *level);
    > +int sev_post_map_gfn(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn);
    > +void sev_post_unmap_gfn(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn);
    > +void handle_rmp_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code);
    > +void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu);
    > +int sev_snp_update_protected_guest_state(struct kvm_vcpu *vcpu);
    >
    > /* vmenter.S */
    >
    > --
    > 2.25.1
    >

    \
     
     \ /
      Last update: 2022-08-18 05:49    [W:2.728 / U:0.844 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site