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Wed, 14 May 2025 00:24:38 -0700 (PDT) MIME-Version: 1.0 References: <20250513163438.3942405-1-tabba@google.com> <20250513163438.3942405-11-tabba@google.com> <55215c60-f071-474b-a0d5-06f27bc97d32@amd.com> In-Reply-To: <55215c60-f071-474b-a0d5-06f27bc97d32@amd.com> From: Fuad Tabba Date: Wed, 14 May 2025 08:24:01 +0100 X-Gm-Features: AX0GCFs_MeHq9AaII05Iub_BF1mqk5thKbzo61ouX2u1qDGHF-RKWUHX1ULEcOk Message-ID: Subject: Re: [PATCH v9 10/17] KVM: x86: Compute max_mapping_level with input from guest_memfd To: Shivank Garg Cc: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, david@redhat.com, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam10 X-Stat-Signature: ktkftkcwpud1qtcjs5ttrprazymcgzdm X-Rspamd-Queue-Id: D064380007 X-Rspam-User: X-HE-Tag: 1747207479-808498 X-HE-Meta: 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 GYrSPDKV Pt4AkhtpxoFlnGJylbxB/F/mYBShfcO0D34KXTxyDV6HY/WaRrSCmrVoSMVGc9UIdJJkwsoNfL4tg1+CGlXU/ErvOoFSlBjPAp3E385q2RNf/MIKafTgFGkHgBjs45lqZj3RmJ7fNkTRewR5FFashrbyVZQEzACI1nTV7+AdV0x/sTxMuRhCcAlxGUVHBkcT3zjhKo2PBbKLDo/dFRPKzRnro9p+7AljHdNgbjPcOjkCWF4D346TFLPj9wapNJWKmyDsiAp9N6t3TCtCne3uuI+q44ZqwxwktM2Vsi+AUwwqnimAeTFyartJbf7wsY2eB+8rnPDnPyJok31WmDnP46NSUR13XJdBwybAR2zWjt0PNfDU= 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: List-Subscribe: List-Unsubscribe: On Wed, 14 May 2025 at 08:14, Shivank Garg wrote: > > On 5/13/2025 10:04 PM, Fuad Tabba wrote: > > From: Ackerley Tng > > > > This patch adds kvm_gmem_max_mapping_level(), which always returns > > PG_LEVEL_4K since guest_memfd only supports 4K pages for now. > > > > When guest_memfd supports shared memory, max_mapping_level (especially > > when recovering huge pages - see call to __kvm_mmu_max_mapping_level() > > from recover_huge_pages_range()) should take input from > > guest_memfd. > > > > Input from guest_memfd should be taken in these cases: > > > > + if the memslot supports shared memory (guest_memfd is used for > > shared memory, or in future both shared and private memory) or > > + if the memslot is only used for private memory and that gfn is > > private. > > > > If the memslot doesn't use guest_memfd, figure out the > > max_mapping_level using the host page tables like before. > > > > This patch also refactors and inlines the other call to > > __kvm_mmu_max_mapping_level(). > > > > In kvm_mmu_hugepage_adjust(), guest_memfd's input is already > > provided (if applicable) in fault->max_level. Hence, there is no need > > to query guest_memfd. > > > > lpage_info is queried like before, and then if the fault is not from > > guest_memfd, adjust fault->req_level based on input from host page > > tables. > > > > Signed-off-by: Ackerley Tng > > Signed-off-by: Fuad Tabba > > --- > > arch/x86/kvm/mmu/mmu.c | 92 ++++++++++++++++++++++++++-------------- > > include/linux/kvm_host.h | 7 +++ > > virt/kvm/guest_memfd.c | 12 ++++++ > > 3 files changed, 79 insertions(+), 32 deletions(-) > > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > index cfbb471f7c70..9e0bc8114859 100644 > > --- a/arch/x86/kvm/mmu/mmu.c > > +++ b/arch/x86/kvm/mmu/mmu.c > > @@ -3256,12 +3256,11 @@ static int host_pfn_mapping_level(struct kvm *kvm, gfn_t gfn, > > return level; > > } > > > > -static int __kvm_mmu_max_mapping_level(struct kvm *kvm, > > - const struct kvm_memory_slot *slot, > > - gfn_t gfn, int max_level, bool is_private) > > +static int kvm_lpage_info_max_mapping_level(struct kvm *kvm, > > + const struct kvm_memory_slot *slot, > > + gfn_t gfn, int max_level) > > { > > struct kvm_lpage_info *linfo; > > - int host_level; > > > > max_level = min(max_level, max_huge_page_level); > > for ( ; max_level > PG_LEVEL_4K; max_level--) { > > @@ -3270,23 +3269,61 @@ static int __kvm_mmu_max_mapping_level(struct kvm *kvm, > > break; > > } > > > > - if (is_private) > > - return max_level; > > + return max_level; > > +} > > + > > +static inline u8 kvm_max_level_for_order(int order) > > +{ > > + BUILD_BUG_ON(KVM_MAX_HUGEPAGE_LEVEL > PG_LEVEL_1G); > > + > > + KVM_MMU_WARN_ON(order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_1G) && > > + order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_2M) && > > + order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_4K)); > > + > > + if (order >= KVM_HPAGE_GFN_SHIFT(PG_LEVEL_1G)) > > + return PG_LEVEL_1G; > > + > > + if (order >= KVM_HPAGE_GFN_SHIFT(PG_LEVEL_2M)) > > + return PG_LEVEL_2M; > > + > > + return PG_LEVEL_4K; > > +} > > + > > +static inline int kvm_gmem_max_mapping_level(const struct kvm_memory_slot *slot, > > + gfn_t gfn, int max_level) > > +{ > > + int max_order; > > > > if (max_level == PG_LEVEL_4K) > > return PG_LEVEL_4K; > > > > - host_level = host_pfn_mapping_level(kvm, gfn, slot); > > - return min(host_level, max_level); > > + max_order = kvm_gmem_mapping_order(slot, gfn); > > + return min(max_level, kvm_max_level_for_order(max_order)); > > } > > > > int kvm_mmu_max_mapping_level(struct kvm *kvm, > > const struct kvm_memory_slot *slot, gfn_t gfn) > > { > > - bool is_private = kvm_slot_has_gmem(slot) && > > - kvm_mem_is_private(kvm, gfn); > > + int max_level; > > + > > + max_level = kvm_lpage_info_max_mapping_level(kvm, slot, gfn, PG_LEVEL_NUM); > > + if (max_level == PG_LEVEL_4K) > > + return PG_LEVEL_4K; > > > > - return __kvm_mmu_max_mapping_level(kvm, slot, gfn, PG_LEVEL_NUM, is_private); > > + if (kvm_slot_has_gmem(slot) && > > + (kvm_gmem_memslot_supports_shared(slot) || > > + kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE)) { > > + return kvm_gmem_max_mapping_level(slot, gfn, max_level); > > + } > > + > > + return min(max_level, host_pfn_mapping_level(kvm, gfn, slot)); > > +} > > + > > +static inline bool fault_from_gmem(struct kvm_page_fault *fault) > > +{ > > + return fault->is_private || > > + (kvm_slot_has_gmem(fault->slot) && > > + kvm_gmem_memslot_supports_shared(fault->slot)); > > } > > > > void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) > > @@ -3309,12 +3346,20 @@ void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault > > * Enforce the iTLB multihit workaround after capturing the requested > > * level, which will be used to do precise, accurate accounting. > > */ > > - fault->req_level = __kvm_mmu_max_mapping_level(vcpu->kvm, slot, > > - fault->gfn, fault->max_level, > > - fault->is_private); > > + fault->req_level = kvm_lpage_info_max_mapping_level(vcpu->kvm, slot, > > + fault->gfn, fault->max_level); > > if (fault->req_level == PG_LEVEL_4K || fault->huge_page_disallowed) > > return; > > > > + if (!fault_from_gmem(fault)) { > > + int host_level; > > + > > + host_level = host_pfn_mapping_level(vcpu->kvm, fault->gfn, slot); > > + fault->req_level = min(fault->req_level, host_level); > > + if (fault->req_level == PG_LEVEL_4K) > > + return; > > + } > > + > > /* > > * mmu_invalidate_retry() was successful and mmu_lock is held, so > > * the pmd can't be split from under us. > > @@ -4448,23 +4493,6 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work) > > vcpu->stat.pf_fixed++; > > } > > > > -static inline u8 kvm_max_level_for_order(int order) > > -{ > > - BUILD_BUG_ON(KVM_MAX_HUGEPAGE_LEVEL > PG_LEVEL_1G); > > - > > - KVM_MMU_WARN_ON(order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_1G) && > > - order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_2M) && > > - order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_4K)); > > - > > - if (order >= KVM_HPAGE_GFN_SHIFT(PG_LEVEL_1G)) > > - return PG_LEVEL_1G; > > - > > - if (order >= KVM_HPAGE_GFN_SHIFT(PG_LEVEL_2M)) > > - return PG_LEVEL_2M; > > - > > - return PG_LEVEL_4K; > > -} > > - > > static u8 kvm_max_level_for_fault_and_order(struct kvm *kvm, > > struct kvm_page_fault *fault, > > int order) > > @@ -4523,7 +4551,7 @@ static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu, > > { > > unsigned int foll = fault->write ? FOLL_WRITE : 0; > > > > - if (fault->is_private || kvm_gmem_memslot_supports_shared(fault->slot)) > > + if (fault_from_gmem(fault)) > > return kvm_mmu_faultin_pfn_gmem(vcpu, fault); > > > > foll |= FOLL_NOWAIT; > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index de7b46ee1762..f9bb025327c3 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -2560,6 +2560,7 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) > > int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > > gfn_t gfn, kvm_pfn_t *pfn, struct page **page, > > int *max_order); > > +int kvm_gmem_mapping_order(const struct kvm_memory_slot *slot, gfn_t gfn); > > #else > > static inline int kvm_gmem_get_pfn(struct kvm *kvm, > > struct kvm_memory_slot *slot, gfn_t gfn, > > @@ -2569,6 +2570,12 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm, > > KVM_BUG_ON(1, kvm); > > return -EIO; > > } > > +static inline int kvm_gmem_mapping_order(const struct kvm_memory_slot *slot, > > + gfn_t gfn) > > +{ > > + BUG(); > > + return 0; > > +} > > #endif /* CONFIG_KVM_GMEM */ > > > > #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > > index fe0245335c96..b8e247063b20 100644 > > --- a/virt/kvm/guest_memfd.c > > +++ b/virt/kvm/guest_memfd.c > > @@ -774,6 +774,18 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > > } > > EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn); > > > > +/** > > + * Returns the mapping order for this @gfn in @slot. > > + * > > + * This is equal to max_order that would be returned if kvm_gmem_get_pfn() were > > + * called now. > > + */ > make W=1 ./ -s generates following warnings- > > warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst > * Returns the mapping order for this @gfn in @slot > > This will fix it. Thank you! /fuad > Subject: [PATCH] tmp > > Signed-off-by: Shivank Garg > --- > virt/kvm/guest_memfd.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index b8e247063b20..d880b9098cc0 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -775,10 +775,12 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn); > > /** > - * Returns the mapping order for this @gfn in @slot. > + * kvm_gmem_mapping_order - Get the mapping order for a GFN. > + * @slot: The KVM memory slot containing the @gfn. > + * @gfn: The guest frame number to check. > * > - * This is equal to max_order that would be returned if kvm_gmem_get_pfn() were > - * called now. > + * Returns: The mapping order for a @gfn in @slot. This is equal to max_order > + * that kvm_gmem_get_pfn() would return for this @gfn. > */ > int kvm_gmem_mapping_order(const struct kvm_memory_slot *slot, gfn_t gfn) > { > -- > 2.34.1 > > Thanks, > Shivank > > > > +int kvm_gmem_mapping_order(const struct kvm_memory_slot *slot, gfn_t gfn) > > +{ > > + return 0; > > +} > > +EXPORT_SYMBOL_GPL(kvm_gmem_mapping_order); > > + > > #ifdef CONFIG_KVM_GENERIC_GMEM_POPULATE > > long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long npages, > > kvm_gmem_populate_cb post_populate, void *opaque) >