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Wed, 14 Jun 2023 09:47:10 -0700 (PDT) Date: Wed, 14 Jun 2023 09:47:09 -0700 From: Isaku Yamahata To: Michael Roth Cc: kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, jroedel@suse.de, thomas.lendacky@amd.com, hpa@zytor.com, ardb@kernel.org, pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com, jmattson@google.com, luto@kernel.org, dave.hansen@linux.intel.com, slp@redhat.com, pgonda@google.com, peterz@infradead.org, srinivas.pandruvada@linux.intel.com, rientjes@google.com, dovmurik@linux.ibm.com, tobin@ibm.com, bp@alien8.de, vbabka@suse.cz, kirill@shutemov.name, ak@linux.intel.com, tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com, dgilbert@redhat.com, jarkko@kernel.org, ashish.kalra@amd.com, nikunj.dadhania@amd.com, liam.merwick@oracle.com, zhi.a.wang@intel.com, isaku.yamahata@gmail.com Subject: Re: [PATCH RFC v9 04/51] KVM: x86: Determine shared/private faults using a configurable mask Message-ID: <20230614164709.GT2244082@ls.amr.corp.intel.com> References: <20230612042559.375660-1-michael.roth@amd.com> <20230612042559.375660-5-michael.roth@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230612042559.375660-5-michael.roth@amd.com> X-Rspamd-Queue-Id: 2B28B4001B X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: qee6srxdgtw4bmretd3dp7zhezw8ygut X-HE-Tag: 1686761232-871109 X-HE-Meta: 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 3fM0i41T 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 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 Sun, Jun 11, 2023 at 11:25:12PM -0500, Michael Roth wrote: > This will be used to determine whether or not an #NPF should be serviced > using a normal page vs. a guarded/gmem one. > > Signed-off-by: Michael Roth > --- > arch/x86/include/asm/kvm_host.h | 7 +++++++ > arch/x86/kvm/mmu/mmu_internal.h | 35 ++++++++++++++++++++++++++++++++- > 2 files changed, 41 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index b3bd24f2a390..c26f76641121 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1445,6 +1445,13 @@ struct kvm_arch { > */ > #define SPLIT_DESC_CACHE_MIN_NR_OBJECTS (SPTE_ENT_PER_PAGE + 1) > struct kvm_mmu_memory_cache split_desc_cache; > + > + /* > + * When set, used to determine whether a fault should be treated as > + * private in the context of protected VMs which use a separate gmem > + * pool to back private guest pages. > + */ > + u64 mmu_private_fault_mask; > }; > > struct kvm_vm_stat { > diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h > index 780b91e1da9f..9b9e75aa43f4 100644 > --- a/arch/x86/kvm/mmu/mmu_internal.h > +++ b/arch/x86/kvm/mmu/mmu_internal.h > @@ -252,6 +252,39 @@ struct kvm_page_fault { > > int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault); > > +static bool kvm_mmu_fault_is_private(struct kvm *kvm, gpa_t gpa, u64 err) > +{ > + struct kvm_memory_slot *slot; > + bool private_fault = false; > + gfn_t gfn = gpa_to_gfn(gpa); > + > + slot = gfn_to_memslot(kvm, gfn); > + if (!slot) { > + pr_debug("%s: no slot, GFN: 0x%llx\n", __func__, gfn); > + goto out; > + } > + > + if (!kvm_slot_can_be_private(slot)) { > + pr_debug("%s: slot is not private, GFN: 0x%llx\n", __func__, gfn); > + goto out; > + } > + > + if (kvm->arch.mmu_private_fault_mask) { > + private_fault = !!(err & kvm->arch.mmu_private_fault_mask); > + goto out; > + } What's the convention of err? Can we abstract it by introducing a new bit PFERR_PRIVATE_MASK? The caller sets it based on arch specific value. the logic will be .is_private = err & PFERR_PRIVATE_MASK; > + > + /* > + * Handling below is for UPM self-tests and guests that treat userspace > + * as the authority on whether a fault should be private or not. > + */ > + private_fault = kvm_mem_is_private(kvm, gpa >> PAGE_SHIFT); This code path is sad. One extra slot lookup and xarray look up. Without mmu lock, the result can change by other vcpu. Let's find a better way. > + > +out: > + pr_debug("%s: GFN: 0x%llx, private: %d\n", __func__, gfn, private_fault); > + return private_fault; > +} > + > /* > * Return values of handle_mmio_page_fault(), mmu.page_fault(), fast_page_fault(), > * and of course kvm_mmu_do_page_fault(). > @@ -301,7 +334,7 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, > .max_level = KVM_MAX_HUGEPAGE_LEVEL, > .req_level = PG_LEVEL_4K, > .goal_level = PG_LEVEL_4K, > - .is_private = kvm_mem_is_private(vcpu->kvm, cr2_or_gpa >> PAGE_SHIFT), > + .is_private = kvm_mmu_fault_is_private(vcpu->kvm, cr2_or_gpa, err), > }; > int r; > > -- > 2.25.1 > -- Isaku Yamahata