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dkim=pass header.d=google.com header.s=20210112 header.b=WxDKd5Bv; spf=pass (imf17.hostedemail.com: domain of alpergun@google.com designates 209.85.166.48 as permitted sender) smtp.mailfrom=alpergun@google.com; dmarc=pass (policy=reject) header.from=google.com X-Stat-Signature: 18455ktmeaxa75338su1praju1z3bf4x X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: DF9E240029 X-Rspam-User: X-HE-Tag: 1665439434-560611 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jun 20, 2022 at 4:13 PM Ashish Kalra wrote: > > From: Brijesh Singh > > When SEV-SNP is enabled in the guest, the hardware places restrictions on > all memory accesses based on the contents of the RMP table. When hardware > encounters RMP check failure caused by the guest memory access it raises > the #NPF. The error code contains additional information on the access > type. See the APM volume 2 for additional information. > > Signed-off-by: Brijesh Singh > --- > arch/x86/kvm/svm/sev.c | 76 ++++++++++++++++++++++++++++++++++++++++++ > arch/x86/kvm/svm/svm.c | 14 +++++--- > 2 files changed, 86 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 4ed90331bca0..7fc0fad87054 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -4009,3 +4009,79 @@ void sev_post_unmap_gfn(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn) > > spin_unlock(&sev->psc_lock); > } > + > +void handle_rmp_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code) > +{ > + int rmp_level, npt_level, rc, assigned; > + struct kvm *kvm = vcpu->kvm; > + gfn_t gfn = gpa_to_gfn(gpa); > + bool need_psc = false; > + enum psc_op psc_op; > + kvm_pfn_t pfn; > + bool private; > + > + write_lock(&kvm->mmu_lock); > + > + if (unlikely(!kvm_mmu_get_tdp_walk(vcpu, gpa, &pfn, &npt_level))) > + goto unlock; > + > + assigned = snp_lookup_rmpentry(pfn, &rmp_level); > + if (unlikely(assigned < 0)) > + goto unlock; > + > + private = !!(error_code & PFERR_GUEST_ENC_MASK); > + > + /* > + * If the fault was due to size mismatch, or NPT and RMP page level's > + * are not in sync, then use PSMASH to split the RMP entry into 4K. > + */ > + if ((error_code & PFERR_GUEST_SIZEM_MASK) || > + (npt_level == PG_LEVEL_4K && rmp_level == PG_LEVEL_2M && private)) { > + rc = snp_rmptable_psmash(kvm, pfn); Regarding this case: RMP level is 4K Page table level is 2M Does this also cause a page fault with size mismatch? If so, we shouldn't try psmash because the rmp entry is already 4K. I see these errors in our tests and I think it may be happening because rmp size is already 4K. [ 1848.752952] psmash failed, gpa 0x191560000 pfn 0x536cd60 rc 7 [ 2922.879635] psmash failed, gpa 0x102830000 pfn 0x37c8230 rc 7 [ 3010.983090] psmash failed, gpa 0x104220000 pfn 0x6cf1e20 rc 7 [ 3170.792050] psmash failed, gpa 0x108a80000 pfn 0x20e0080 rc 7 [ 3345.955147] psmash failed, gpa 0x11b480000 pfn 0x1545e480 rc 7 Shouldn't we use AND instead of OR in the if statement? if ((error_code & PFERR_GUEST_SIZEM_MASK) && ... > + if (rc) > + pr_err_ratelimited("psmash failed, gpa 0x%llx pfn 0x%llx rc %d\n", > + gpa, pfn, rc); > + goto out; > + } > + > + /* > + * If it's a private access, and the page is not assigned in the > + * RMP table, create a new private RMP entry. This can happen if > + * guest did not use the PSC VMGEXIT to transition the page state > + * before the access. > + */ > + if (!assigned && private) { > + need_psc = 1; > + psc_op = SNP_PAGE_STATE_PRIVATE; > + goto out; > + } > + > + /* > + * If it's a shared access, but the page is private in the RMP table > + * then make the page shared in the RMP table. This can happen if > + * the guest did not use the PSC VMGEXIT to transition the page > + * state before the access. > + */ > + if (assigned && !private) { > + need_psc = 1; > + psc_op = SNP_PAGE_STATE_SHARED; > + } > + > +out: > + write_unlock(&kvm->mmu_lock); > + > + if (need_psc) > + rc = __snp_handle_page_state_change(vcpu, psc_op, gpa, PG_LEVEL_4K); > + > + /* > + * The fault handler has updated the RMP pagesize, zap the existing > + * rmaps for large entry ranges so that nested page table gets rebuilt > + * with the updated RMP pagesize. > + */ > + gfn = gpa_to_gfn(gpa) & ~(KVM_PAGES_PER_HPAGE(PG_LEVEL_2M) - 1); > + kvm_zap_gfn_range(kvm, gfn, gfn + PTRS_PER_PMD); > + return; > + > +unlock: > + write_unlock(&kvm->mmu_lock); > +} > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 1c8e035ba011..7742bc986afc 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -1866,15 +1866,21 @@ static int pf_interception(struct kvm_vcpu *vcpu) > static int npf_interception(struct kvm_vcpu *vcpu) > { > struct vcpu_svm *svm = to_svm(vcpu); > + int rc; > > u64 fault_address = svm->vmcb->control.exit_info_2; > u64 error_code = svm->vmcb->control.exit_info_1; > > trace_kvm_page_fault(fault_address, error_code); > - return kvm_mmu_page_fault(vcpu, fault_address, error_code, > - static_cpu_has(X86_FEATURE_DECODEASSISTS) ? > - svm->vmcb->control.insn_bytes : NULL, > - svm->vmcb->control.insn_len); > + rc = kvm_mmu_page_fault(vcpu, fault_address, error_code, > + static_cpu_has(X86_FEATURE_DECODEASSISTS) ? > + svm->vmcb->control.insn_bytes : NULL, > + svm->vmcb->control.insn_len); > + > + if (error_code & PFERR_GUEST_RMP_MASK) > + handle_rmp_page_fault(vcpu, fault_address, error_code); > + > + return rc; > } > > static int db_interception(struct kvm_vcpu *vcpu) > -- > 2.25.1 > >