[RFC PATCH v2 4/6] KVM: gmem: Add ioctl to inject memory failure on guest memfd

isaku.yamahata
2023-09-21T20:41:45Z

From: Isaku Yamahata <isaku.yamahata@intel.com>

To test error_remove_page() method of KVM gmem, add a new ioctl to
inject memory failure based on offset of guest memfd.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
include/uapi/linux/kvm.h | 6 ++++
virt/kvm/guest_mem.c | 68 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 74 insertions(+)

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 65fc983af840..4160614bcc0f 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -2323,4 +2323,10 @@ struct kvm_create_guest_memfd {
__u64 reserved[6];
};

+#define KVM_GUEST_MEMORY_FAILURE _IOWR(KVMIO, 0xd5, struct kvm_guest_memory_failure)
+
+struct kvm_guest_memory_failure {
+ __u64 offset;
+};
+
#endif /* __LINUX_KVM_H */
diff --git a/virt/kvm/guest_mem.c b/virt/kvm/guest_mem.c
index 01fb4ca861d0..bc9dae50004b 100644
--- a/virt/kvm/guest_mem.c
+++ b/virt/kvm/guest_mem.c
@@ -291,10 +291,78 @@ static struct file *kvm_gmem_get_file(struct kvm_memory_slot *slot)
return file;
}

+static int kvm_gmem_inject_failure(struct file *file,
+ struct kvm_guest_memory_failure *mf)
+{
+ struct inode *inode = file_inode(file);
+ struct address_space *mapping = inode->i_mapping;
+ pgoff_t index = mf->offset >> PAGE_SHIFT;
+ struct folio *folio;
+ unsigned long pfn;
+ int err = 0;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ filemap_invalidate_lock_shared(mapping);
+
+ /* Don't allocate page. */
+ folio = filemap_get_folio(mapping, index);
+ if (!folio) {
+ err = -ENOENT;
+ goto out;
+ }
+ if (IS_ERR(folio)) {
+ err = PTR_ERR(folio);
+ goto out;
+ }
+
+ pfn = folio_pfn(folio) + (index - folio_index(folio));
+ folio_put(folio);
+
+out:
+ filemap_invalidate_unlock_shared(mapping);
+ if (err)
+ return err;
+
+ /*
+ * Race with pfn: memory_failure() and unpoison_memory() gain invalidate
+ * lock as the error recovery logic tries to remove pages from
+ * mapping.
+ */
+ if (!pfn_valid(pfn))
+ return -ENXIO;
+ return memory_failure(pfn, MF_SW_SIMULATED);
+}
+
+static long kvm_gmem_ioctl(struct file *file, unsigned int ioctl,
+ unsigned long arg)
+{
+ void __user *argp = (void __user *)arg;
+ int r = -EINVAL;
+
+ switch (ioctl) {
+ case KVM_GUEST_MEMORY_FAILURE: {
+ struct kvm_guest_memory_failure mf;
+
+ r = -EFAULT;
+ if (copy_from_user(&mf, argp, sizeof(mf)))
+ break;
+ r = kvm_gmem_inject_failure(file, &mf);
+ break;
+ }
+ default:
+ break;
+ }
+
+ return r;
+}
+
static const struct file_operations kvm_gmem_fops = {
.open = generic_file_open,
.release = kvm_gmem_release,
.fallocate = kvm_gmem_fallocate,
+ .unlocked_ioctl = kvm_gmem_ioctl,
};

static int kvm_gmem_migrate_folio(struct address_space *mapping,
--
2.25.1