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AJvYcCWP3s9fLDXycW0FU5T7ikINfyeNOBcYMckaM/GVBqaudrzdB030j/BqyxgRXBkv7NO3oPFhTRX/5Oh+Jxzg@vger.kernel.org X-Gm-Message-State: AOJu0YwH3uBPRfDvbvW3LN02DqRT/9ZTkUnA+VqIHgVe0pOCemr0zWb+ JyrsZ9fuoiDY18Wz+PFpQihrNI23/ANiZRWLlxWOaFpy3iIkwBW6DOO2ntBGGl1VI0PQcVk6VJX L2Y+Orw== X-Google-Smtp-Source: AGHT+IEXIwkLfUiQJXwnuBxbU39hQL5k325KMiuT8Z+LZslth4tnISdS1AUdYJ8MJLju2XbZxDVZpjWpVZw= X-Received: from pgbfq26.prod.google.com ([2002:a05:6a02:299a:b0:b39:311c:59fd]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:32a3:b0:235:5f88:32fc with SMTP id adf61e73a8af0-23d4902451emr14783922637.18.1753396326379; Thu, 24 Jul 2025 15:32:06 -0700 (PDT) Date: Thu, 24 Jul 2025 15:32:05 -0700 In-Reply-To: <1ff6a90a-3e03-4104-9833-4b07bb84831f@intel.com> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250723104714.1674617-1-tabba@google.com> <20250723104714.1674617-15-tabba@google.com> <1ff6a90a-3e03-4104-9833-4b07bb84831f@intel.com> Message-ID: Subject: Re: [PATCH v16 14/22] KVM: x86/mmu: Enforce guest_memfd's max order when recovering hugepages From: Sean Christopherson To: Xiaoyao Li Cc: Fuad Tabba , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, kvmarm@lists.linux.dev, pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, 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="us-ascii" On Wed, Jul 23, 2025, Xiaoyao Li wrote: > On 7/23/2025 6:47 PM, Fuad Tabba wrote: ... > > + if (max_level == PG_LEVEL_4K) > > + return max_level; > > + > > + return min(max_level, > > + kvm_x86_call(gmem_max_mapping_level)(kvm, pfn)); > > } > > I don't mean to want a next version. > > But I have to point it out that, the coco_level stuff in the next patch > should be put in this patch actually. Because this patch does the wrong > thing to change from > > req_max_level = kvm_x86_call(gmem_max_mapping_level)(kvm, pfn); > if (req_max_level) > max_level = min(max_level, req_max_level); > > to > > return min(max_level, > kvm_x86_call(gmem_max_mapping_level)(kvm, pfn)); Gah, nice catch. Let's do one more version (knock wood). I have no objection to fixing up my own goof, but the selftest needs to be reworked too, and I think it makes sense for Paolo to grab this directly. The fewer "things" we need to handoff to Paolo, the better. The fixup will generate a minor conflict, but it's trivial to resolve, and the resting state should end up identical. As fixup: --- arch/x86/kvm/mmu/mmu.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 6148cc96f7d4..c4ff8b4028df 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3305,9 +3305,9 @@ static u8 kvm_max_level_for_order(int order) static u8 kvm_max_private_mapping_level(struct kvm *kvm, struct kvm_page_fault *fault, const struct kvm_memory_slot *slot, gfn_t gfn) { + u8 max_level, coco_level; struct page *page; kvm_pfn_t pfn; - u8 max_level; /* For faults, use the gmem information that was resolved earlier. */ if (fault) { @@ -3331,8 +3331,16 @@ static u8 kvm_max_private_mapping_level(struct kvm *kvm, struct kvm_page_fault * if (max_level == PG_LEVEL_4K) return max_level; - return min(max_level, - kvm_x86_call(gmem_max_mapping_level)(kvm, pfn)); + /* + * CoCo may influence the max mapping level, e.g. due to RMP or S-EPT + * restrictions. A return of '0' means "no additional restrictions", to + * allow for using an optional "ret0" static call. + */ + coco_level = kvm_x86_call(gmem_max_mapping_level)(kvm, pfn); + if (coco_level) + max_level = min(max_level, coco_level); + + return max_level; } int kvm_mmu_max_mapping_level(struct kvm *kvm, struct kvm_page_fault *fault, base-commit: f937c99dad18339773f18411f2a0193b5db8b581 -- Or a full patch: From: Sean Christopherson Date: Wed, 23 Jul 2025 11:47:06 +0100 Subject: [PATCH] KVM: x86/mmu: Enforce guest_memfd's max order when recovering hugepages Rework kvm_mmu_max_mapping_level() to consult guest_memfd (and relevant) vendor code when recovering hugepages, e.g. after disabling live migration. The flaw has existed since guest_memfd was originally added, but has gone unnoticed due to lack of guest_memfd hugepage support. Get all information on-demand from the memslot and guest_memfd instance, even though KVM could pull the pfn from the SPTE. However, the max order/level needs to come from guest_memfd, and using kvm_gmem_get_pfn() avoids adding a new gmem API, and avoids having to retrieve the pfn and plumb it into kvm_mmu_max_mapping_level() (the pfn is needed for SNP to consult the RMP). Note, calling kvm_mem_is_private() in the non-fault path is safe, so long as mmu_lock is held, as hugepage recovery operates on shadow-present SPTEs, i.e. calling kvm_mmu_max_mapping_level() with @fault=NULL is mutually exclusive with kvm_vm_set_mem_attributes() changing the PRIVATE attribute of the gfn. Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu/mmu.c | 91 ++++++++++++++++++++------------- arch/x86/kvm/mmu/mmu_internal.h | 2 +- arch/x86/kvm/mmu/tdp_mmu.c | 2 +- 3 files changed, 58 insertions(+), 37 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 20dd9f64156e..c4ff8b4028df 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3302,31 +3302,63 @@ static u8 kvm_max_level_for_order(int order) return PG_LEVEL_4K; } -static u8 kvm_max_private_mapping_level(struct kvm *kvm, kvm_pfn_t pfn, - u8 max_level, int gmem_order) +static u8 kvm_max_private_mapping_level(struct kvm *kvm, struct kvm_page_fault *fault, + const struct kvm_memory_slot *slot, gfn_t gfn) { - u8 req_max_level; + u8 max_level, coco_level; + struct page *page; + kvm_pfn_t pfn; - if (max_level == PG_LEVEL_4K) - return PG_LEVEL_4K; + /* For faults, use the gmem information that was resolved earlier. */ + if (fault) { + pfn = fault->pfn; + max_level = fault->max_level; + } else { + /* TODO: Constify the guest_memfd chain. */ + struct kvm_memory_slot *__slot = (struct kvm_memory_slot *)slot; + int max_order, r; + + r = kvm_gmem_get_pfn(kvm, __slot, gfn, &pfn, &page, &max_order); + if (r) + return PG_LEVEL_4K; + + if (page) + put_page(page); + + max_level = kvm_max_level_for_order(max_order); + } - max_level = min(kvm_max_level_for_order(gmem_order), max_level); if (max_level == PG_LEVEL_4K) - return PG_LEVEL_4K; + return max_level; - req_max_level = kvm_x86_call(gmem_max_mapping_level)(kvm, pfn); - if (req_max_level) - max_level = min(max_level, req_max_level); + /* + * CoCo may influence the max mapping level, e.g. due to RMP or S-EPT + * restrictions. A return of '0' means "no additional restrictions", to + * allow for using an optional "ret0" static call. + */ + coco_level = kvm_x86_call(gmem_max_mapping_level)(kvm, pfn); + if (coco_level) + max_level = min(max_level, coco_level); return max_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) +int kvm_mmu_max_mapping_level(struct kvm *kvm, struct kvm_page_fault *fault, + const struct kvm_memory_slot *slot, gfn_t gfn) { struct kvm_lpage_info *linfo; - int host_level; + int host_level, max_level; + bool is_private; + + lockdep_assert_held(&kvm->mmu_lock); + + if (fault) { + max_level = fault->max_level; + is_private = fault->is_private; + } else { + max_level = PG_LEVEL_NUM; + is_private = kvm_mem_is_private(kvm, gfn); + } max_level = min(max_level, max_huge_page_level); for ( ; max_level > PG_LEVEL_4K; max_level--) { @@ -3335,25 +3367,16 @@ static int __kvm_mmu_max_mapping_level(struct kvm *kvm, break; } + if (max_level == PG_LEVEL_4K) + return PG_LEVEL_4K; + if (is_private) - return max_level; - - if (max_level == PG_LEVEL_4K) - return PG_LEVEL_4K; - - host_level = host_pfn_mapping_level(kvm, gfn, slot); + host_level = kvm_max_private_mapping_level(kvm, fault, slot, gfn); + else + host_level = host_pfn_mapping_level(kvm, gfn, slot); return min(host_level, max_level); } -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); - - return __kvm_mmu_max_mapping_level(kvm, slot, gfn, PG_LEVEL_NUM, is_private); -} - void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_memory_slot *slot = fault->slot; @@ -3374,9 +3397,8 @@ 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_mmu_max_mapping_level(vcpu->kvm, fault, + fault->slot, fault->gfn); if (fault->req_level == PG_LEVEL_4K || fault->huge_page_disallowed) return; @@ -4564,8 +4586,7 @@ static int kvm_mmu_faultin_pfn_private(struct kvm_vcpu *vcpu, } fault->map_writable = !(fault->slot->flags & KVM_MEM_READONLY); - fault->max_level = kvm_max_private_mapping_level(vcpu->kvm, fault->pfn, - fault->max_level, max_order); + fault->max_level = kvm_max_level_for_order(max_order); return RET_PF_CONTINUE; } @@ -7165,7 +7186,7 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm, * mapping if the indirect sp has level = 1. */ if (sp->role.direct && - sp->role.level < kvm_mmu_max_mapping_level(kvm, slot, sp->gfn)) { + sp->role.level < kvm_mmu_max_mapping_level(kvm, NULL, slot, sp->gfn)) { kvm_zap_one_rmap_spte(kvm, rmap_head, sptep); if (kvm_available_flush_remote_tlbs_range()) diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h index 65f3c89d7c5d..b776be783a2f 100644 --- a/arch/x86/kvm/mmu/mmu_internal.h +++ b/arch/x86/kvm/mmu/mmu_internal.h @@ -411,7 +411,7 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, return r; } -int kvm_mmu_max_mapping_level(struct kvm *kvm, +int kvm_mmu_max_mapping_level(struct kvm *kvm, struct kvm_page_fault *fault, const struct kvm_memory_slot *slot, gfn_t gfn); void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault); void disallowed_hugepage_adjust(struct kvm_page_fault *fault, u64 spte, int cur_level); diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 7f3d7229b2c1..740cb06accdb 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1813,7 +1813,7 @@ static void recover_huge_pages_range(struct kvm *kvm, if (iter.gfn < start || iter.gfn >= end) continue; - max_mapping_level = kvm_mmu_max_mapping_level(kvm, slot, iter.gfn); + max_mapping_level = kvm_mmu_max_mapping_level(kvm, NULL, slot, iter.gfn); if (max_mapping_level < iter.level) continue; base-commit: 84ca709e4f4d54aae3b8d4df74490d8d3d2b1272 --