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Fri, 28 Mar 2025 08:31:40 -0700 (PDT) Date: Fri, 28 Mar 2025 15:31:29 +0000 In-Reply-To: <20250328153133.3504118-1-tabba@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250328153133.3504118-1-tabba@google.com> X-Mailer: git-send-email 2.49.0.472.ge94155a9ec-goog Message-ID: <20250328153133.3504118-4-tabba@google.com> Subject: [PATCH v7 3/7] KVM: guest_memfd: Track folio sharing within a struct kvm_gmem_private 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, 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, tabba@google.com Content-Type: text/plain; charset="UTF-8" From: Ackerley Tng Track guest_memfd folio sharing state within the inode, since it is a property of the guest_memfd's memory contents. The guest_memfd PRIVATE memory attribute is not used for two reasons. It reflects the userspace expectation for the memory state, and therefore can be toggled by userspace. Also, although each guest_memfd file has a 1:1 binding with a KVM instance, the plan is to allow multiple files per inode, e.g. to allow intra-host migration to a new KVM instance, without destroying guest_memfd. Signed-off-by: Ackerley Tng Co-developed-by: Vishal Annapurve Signed-off-by: Vishal Annapurve Co-developed-by: Fuad Tabba Signed-off-by: Fuad Tabba --- virt/kvm/guest_memfd.c | 58 ++++++++++++++++++++++++++++++++++++++---- 1 file changed, 53 insertions(+), 5 deletions(-) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index ac6b8853699d..cde16ed3b230 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -17,6 +17,18 @@ struct kvm_gmem { struct list_head entry; }; +struct kvm_gmem_inode_private { +#ifdef CONFIG_KVM_GMEM_SHARED_MEM + struct xarray shared_offsets; + rwlock_t offsets_lock; +#endif +}; + +static struct kvm_gmem_inode_private *kvm_gmem_private(struct inode *inode) +{ + return inode->i_mapping->i_private_data; +} + #ifdef CONFIG_KVM_GMEM_SHARED_MEM void kvm_gmem_handle_folio_put(struct folio *folio) { @@ -324,8 +336,28 @@ static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn) return gfn - slot->base_gfn + slot->gmem.pgoff; } +static void kvm_gmem_evict_inode(struct inode *inode) +{ + struct kvm_gmem_inode_private *private = kvm_gmem_private(inode); + +#ifdef CONFIG_KVM_GMEM_SHARED_MEM + /* + * .evict_inode can be called before private data is set up if there are + * issues during inode creation. + */ + if (private) + xa_destroy(&private->shared_offsets); +#endif + + truncate_inode_pages_final(inode->i_mapping); + + kfree(private); + clear_inode(inode); +} + static const struct super_operations kvm_gmem_super_operations = { - .statfs = simple_statfs, + .statfs = simple_statfs, + .evict_inode = kvm_gmem_evict_inode, }; static int kvm_gmem_init_fs_context(struct fs_context *fc) @@ -553,6 +585,7 @@ static struct inode *kvm_gmem_inode_make_secure_inode(const char *name, loff_t size, u64 flags) { const struct qstr qname = QSTR_INIT(name, strlen(name)); + struct kvm_gmem_inode_private *private; struct inode *inode; int err; @@ -561,10 +594,20 @@ static struct inode *kvm_gmem_inode_make_secure_inode(const char *name, return inode; err = security_inode_init_security_anon(inode, &qname, NULL); - if (err) { - iput(inode); - return ERR_PTR(err); - } + if (err) + goto out; + + err = -ENOMEM; + private = kzalloc(sizeof(*private), GFP_KERNEL); + if (!private) + goto out; + +#ifdef CONFIG_KVM_GMEM_SHARED_MEM + xa_init(&private->shared_offsets); + rwlock_init(&private->offsets_lock); +#endif + + inode->i_mapping->i_private_data = private; inode->i_private = (void *)(unsigned long)flags; inode->i_op = &kvm_gmem_iops; @@ -577,6 +620,11 @@ static struct inode *kvm_gmem_inode_make_secure_inode(const char *name, WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping)); return inode; + +out: + iput(inode); + + return ERR_PTR(err); } static struct file *kvm_gmem_inode_create_getfile(void *priv, loff_t size, -- 2.49.0.472.ge94155a9ec-goog