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AJvYcCVyO9bTOR7uVIwYEY0bPuoVIxYFGx/AW51DapT2WaUB6vtB4Y9xPMr4EALWybpbaT5zA/sMMCQzh+q5cBLU@vger.kernel.org X-Gm-Message-State: AOJu0YzeLstR8aTCF/OgKMqKufZUjGr/J+aoQCQE93Es84JfEeJCaBTK bULQY00Ii1hzFiBSxQM72UtIYYMxBmuNwr8zR/smt02XSeR0igTYJ43qS5qYn/MxQ7DSsRAcIg= = X-Google-Smtp-Source: AGHT+IG7SQRbRuMfYH/Rui+CBChrEOHfesWWRZDd/p/7xcfBTKh/y+cfP2FSghBgXkgmmW6X7QZVv1DCpQ== X-Received: from fuad.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:1613]) (user=tabba job=sendgmr) by 2002:a81:b545:0:b0:6e2:19f3:ff75 with SMTP id 00721157ae682-6e3221a89dbmr187767b3.6.1728550785757; Thu, 10 Oct 2024 01:59:45 -0700 (PDT) Date: Thu, 10 Oct 2024 09:59:24 +0100 In-Reply-To: <20241010085930.1546800-1-tabba@google.com> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241010085930.1546800-1-tabba@google.com> X-Mailer: git-send-email 2.47.0.rc0.187.ge670bccf7e-goog Message-ID: <20241010085930.1546800-6-tabba@google.com> Subject: [PATCH v3 05/11] KVM: guest_memfd: Add guest_memfd support to kvm_(read|/write)_guest_page() From: Fuad Tabba To: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org Cc: 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, yu.c.zhang@linux.intel.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, tabba@google.com Make kvm_(read|/write)_guest_page() capable of accessing guest memory for slots that don't have a userspace address, but only if the memory is mappable, which also indicates that it is accessible by the host. Signed-off-by: Fuad Tabba --- virt/kvm/kvm_main.c | 137 ++++++++++++++++++++++++++++++++++++++------ 1 file changed, 118 insertions(+), 19 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index aed9cf2f1685..77e6412034b9 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3399,23 +3399,114 @@ int kvm_gmem_clear_mappable(struct kvm *kvm, gfn_t start, gfn_t end) return kvm_gmem_toggle_mappable(kvm, start, end, false); } +static int __kvm_read_guest_memfd_page(struct kvm *kvm, + struct kvm_memory_slot *slot, + gfn_t gfn, void *data, int offset, + int len) +{ + struct page *page; + u64 pfn; + int r; + + /* + * Holds the folio lock until after checking whether it can be faulted + * in, to avoid races with paths that change a folio's mappability. + */ + r = kvm_gmem_get_pfn_locked(kvm, slot, gfn, &pfn, NULL); + if (r) + return r; + + page = pfn_to_page(pfn); + + if (!kvm_gmem_is_mappable(kvm, gfn, gfn + 1)) { + r = -EPERM; + goto unlock; + } + memcpy(data, page_address(page) + offset, len); +unlock: + if (r) + put_page(page); + else + kvm_release_pfn_clean(pfn); + unlock_page(page); + + return r; +} + +static int __kvm_write_guest_memfd_page(struct kvm *kvm, + struct kvm_memory_slot *slot, + gfn_t gfn, const void *data, + int offset, int len) +{ + struct page *page; + u64 pfn; + int r; + + /* + * Holds the folio lock until after checking whether it can be faulted + * in, to avoid races with paths that change a folio's mappability. + */ + r = kvm_gmem_get_pfn_locked(kvm, slot, gfn, &pfn, NULL); + if (r) + return r; + + page = pfn_to_page(pfn); + + if (!kvm_gmem_is_mappable(kvm, gfn, gfn + 1)) { + r = -EPERM; + goto unlock; + } + memcpy(page_address(page) + offset, data, len); +unlock: + if (r) + put_page(page); + else + kvm_release_pfn_dirty(pfn); + unlock_page(page); + + return r; +} +#else +static int __kvm_read_guest_memfd_page(struct kvm *kvm, + struct kvm_memory_slot *slot, + gfn_t gfn, void *data, int offset, + int len) +{ + WARN_ON_ONCE(1); + return -EIO; +} + +static int __kvm_write_guest_memfd_page(struct kvm *kvm, + struct kvm_memory_slot *slot, + gfn_t gfn, const void *data, + int offset, int len) +{ + WARN_ON_ONCE(1); + return -EIO; +} #endif /* CONFIG_KVM_GMEM_MAPPABLE */ /* Copy @len bytes from guest memory at '(@gfn * PAGE_SIZE) + @offset' to @data */ -static int __kvm_read_guest_page(struct kvm_memory_slot *slot, gfn_t gfn, - void *data, int offset, int len) + +static int __kvm_read_guest_page(struct kvm *kvm, struct kvm_memory_slot *slot, + gfn_t gfn, void *data, int offset, int len) { - int r; unsigned long addr; if (WARN_ON_ONCE(offset + len > PAGE_SIZE)) return -EFAULT; + if (IS_ENABLED(CONFIG_KVM_GMEM_MAPPABLE) && + kvm_slot_can_be_private(slot) && + !slot->userspace_addr) { + return __kvm_read_guest_memfd_page(kvm, slot, gfn, data, + offset, len); + } + addr = gfn_to_hva_memslot_prot(slot, gfn, NULL); if (kvm_is_error_hva(addr)) return -EFAULT; - r = __copy_from_user(data, (void __user *)addr + offset, len); - if (r) + if (__copy_from_user(data, (void __user *)addr + offset, len)) return -EFAULT; return 0; } @@ -3425,7 +3516,7 @@ int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset, { struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn); - return __kvm_read_guest_page(slot, gfn, data, offset, len); + return __kvm_read_guest_page(kvm, slot, gfn, data, offset, len); } EXPORT_SYMBOL_GPL(kvm_read_guest_page); @@ -3434,7 +3525,7 @@ int kvm_vcpu_read_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn, void *data, { struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn); - return __kvm_read_guest_page(slot, gfn, data, offset, len); + return __kvm_read_guest_page(vcpu->kvm, slot, gfn, data, offset, len); } EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_page); @@ -3511,22 +3602,30 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_atomic); /* Copy @len bytes from @data into guest memory at '(@gfn * PAGE_SIZE) + @offset' */ static int __kvm_write_guest_page(struct kvm *kvm, - struct kvm_memory_slot *memslot, gfn_t gfn, - const void *data, int offset, int len) + struct kvm_memory_slot *slot, gfn_t gfn, + const void *data, int offset, int len) { - int r; - unsigned long addr; - if (WARN_ON_ONCE(offset + len > PAGE_SIZE)) return -EFAULT; - addr = gfn_to_hva_memslot(memslot, gfn); - if (kvm_is_error_hva(addr)) - return -EFAULT; - r = __copy_to_user((void __user *)addr + offset, data, len); - if (r) - return -EFAULT; - mark_page_dirty_in_slot(kvm, memslot, gfn); + if (IS_ENABLED(CONFIG_KVM_GMEM_MAPPABLE) && + kvm_slot_can_be_private(slot) && + !slot->userspace_addr) { + int r = __kvm_write_guest_memfd_page(kvm, slot, gfn, data, + offset, len); + + if (r) + return r; + } else { + unsigned long addr = gfn_to_hva_memslot(slot, gfn); + + if (kvm_is_error_hva(addr)) + return -EFAULT; + if (__copy_to_user((void __user *)addr + offset, data, len)) + return -EFAULT; + } + + mark_page_dirty_in_slot(kvm, slot, gfn); return 0; }