[PATCH Part2 v6 49/49] KVM: SVM: Sync the GHCB scratch buffer using already mapped ghcb
From: Ashish Kalra <Ashish.Kalra@amd.com>
Date: 2022-06-20 23:21:46
Also in:
kvm, linux-crypto, linux-mm, lkml
Subsystem:
kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Ashish Kalra <ashish.kalra@amd.com> Using kvm_write_guest() to sync the GHCB scratch buffer can fail due to host mapping being 2M, but RMP being 4K. The page fault handling in do_user_addr_fault() fails to split the 2M page to handle RMP fault due to it being called here in a non-preemptible context. Instead use the already kernel mapped ghcb to sync the scratch buffer when the scratch buffer is contained within the GHCB. Signed-off-by: Ashish Kalra <ashish.kalra@amd.com> --- arch/x86/kvm/svm/sev.c | 29 +++++++++++++++++++++-------- arch/x86/kvm/svm/svm.h | 2 ++ 2 files changed, 23 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 2c88215a111f..e1dd67e12774 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c@@ -2944,6 +2944,24 @@ static bool sev_es_sync_to_ghcb(struct vcpu_svm *svm) ghcb_set_sw_exit_info_1(ghcb, svm->sev_es.ghcb_sw_exit_info_1); ghcb_set_sw_exit_info_2(ghcb, svm->sev_es.ghcb_sw_exit_info_2); + /* Sync the scratch buffer area. */ + if (svm->sev_es.ghcb_sa_sync) { + if (svm->sev_es.ghcb_sa_contained) { + memcpy(ghcb->shared_buffer + svm->sev_es.ghcb_sa_offset, + svm->sev_es.ghcb_sa, svm->sev_es.ghcb_sa_len); + } else { + int ret; + + ret = kvm_write_guest(svm->vcpu.kvm, + svm->sev_es.ghcb_sa_gpa, + svm->sev_es.ghcb_sa, svm->sev_es.ghcb_sa_len); + if (ret) + pr_warn_ratelimited("unmap_ghcb: kvm_write_guest failed while syncing scratch area, gpa: %llx, ret: %d\n", + svm->sev_es.ghcb_sa_gpa, ret); + } + svm->sev_es.ghcb_sa_sync = false; + } + trace_kvm_vmgexit_exit(svm->vcpu.vcpu_id, ghcb); svm_unmap_ghcb(svm, &map);
@@ -3156,14 +3174,6 @@ void sev_es_unmap_ghcb(struct vcpu_svm *svm) if (!svm->sev_es.ghcb_in_use) return; - /* Sync the scratch buffer area. */ - if (svm->sev_es.ghcb_sa_sync) { - kvm_write_guest(svm->vcpu.kvm, - svm->sev_es.ghcb_sa_gpa, - svm->sev_es.ghcb_sa, svm->sev_es.ghcb_sa_len); - svm->sev_es.ghcb_sa_sync = false; - } - sev_es_sync_to_ghcb(svm); svm->sev_es.ghcb_in_use = false;
@@ -3229,6 +3239,8 @@ static int setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len) scratch_gpa_beg, scratch_gpa_end); goto e_scratch; } + svm->sev_es.ghcb_sa_contained = true; + svm->sev_es.ghcb_sa_offset = scratch_gpa_beg - ghcb_scratch_beg; } else { /* * The guest memory must be read into a kernel buffer, so
@@ -3239,6 +3251,7 @@ static int setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len) len, GHCB_SCRATCH_AREA_LIMIT); goto e_scratch; } + svm->sev_es.ghcb_sa_contained = false; } if (svm->sev_es.ghcb_sa_alloc_len < len) {
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 7b14b5ef1f8c..2cdfc79bf2cf 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h@@ -210,6 +210,8 @@ struct vcpu_sev_es_state { u64 ghcb_sa_gpa; u32 ghcb_sa_alloc_len; bool ghcb_sa_sync; + bool ghcb_sa_contained; + u32 ghcb_sa_offset; /* * SEV-ES support to hold the sw_exit_info return values to be
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2.25.1