linux-kernel - [PATCH 2/4] KVM: add KVM_GUEST_MEMFD_POPULATE ioctl for guest

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Message-ID: <20241024095429.54052-3-kalyazin@amazon.com>
Date: Thu, 24 Oct 2024 09:54:27 +0000
From: Nikita Kalyazin <kalyazin@...zon.com>
To: <pbonzini@...hat.com>, <corbet@....net>, <kvm@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <jthoughton@...gle.com>, <brijesh.singh@....com>, <michael.roth@....com>,
	<graf@...zon.de>, <jgowans@...zon.com>, <roypat@...zon.co.uk>,
	<derekmn@...zon.com>, <nsaenz@...zon.es>, <xmarcalx@...zon.com>,
	<kalyazin@...zon.com>
Subject: [PATCH 2/4] KVM: add KVM_GUEST_MEMFD_POPULATE ioctl for guest_memfd

The ioctl populates guest_memfd with userspace-provided data.

Signed-off-by: Nikita Kalyazin <kalyazin@...zon.com>
---
 include/linux/kvm_host.h |  3 +++
 include/uapi/linux/kvm.h |  9 +++++++++
 virt/kvm/guest_memfd.c   |  7 +++++++
 virt/kvm/kvm_main.c      | 10 ++++++++++
 4 files changed, 29 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index db567d26f7b9..5b0347783598 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2505,6 +2505,9 @@ typedef int (*kvm_gmem_populate_cb)(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
 
 long kvm_gmem_populate(struct kvm *kvm, gfn_t gfn, void __user *src, long npages,
 		       kvm_gmem_populate_cb post_populate, void *opaque);
+
+int kvm_gmem_guest_memfd_populate(struct kvm *kvm,
+				struct kvm_guest_memfd_populate *populate);
 #endif
 
 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 637efc055145..5d8073de0d96 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1573,4 +1573,13 @@ struct kvm_pre_fault_memory {
 	__u64 padding[5];
 };
 
+struct kvm_guest_memfd_populate {
+	__u64 gpa;
+	__u64 size;
+	void __user *from;
+	__u64 flags;
+};
+
+#define KVM_GUEST_MEMFD_POPULATE _IOW(KVMIO,  0xd6, struct kvm_guest_memfd_populate)
+
 #endif /* __LINUX_KVM_H */
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 954312fac462..08630b87f0e3 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -720,4 +720,11 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long
 	return ret && !i ? ret : i;
 }
 EXPORT_SYMBOL_GPL(kvm_gmem_populate);
+
+int kvm_gmem_guest_memfd_populate(struct kvm *kvm,
+				struct kvm_guest_memfd_populate *populate)
+{
+	return kvm_gmem_populate(kvm, populate->gpa >> PAGE_SHIFT, populate->from,
+		populate->size >> PAGE_SHIFT, kvm_gmem_post_populate_generic, NULL);
+}
 #endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 05cbb2548d99..e5bd2c0031bf 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -5383,6 +5383,16 @@ static long kvm_vm_ioctl(struct file *filp,
 		r = kvm_gmem_create(kvm, &guest_memfd);
 		break;
 	}
+	case KVM_GUEST_MEMFD_POPULATE: {
+		struct kvm_guest_memfd_populate populate;
+
+		r = -EFAULT;
+		if (copy_from_user(&populate, argp, sizeof(populate)))
+			goto out;
+
+		r = kvm_gmem_guest_memfd_populate(kvm, &populate);
+		break;
+	}
 #endif
 	default:
 		r = kvm_arch_vm_ioctl(filp, ioctl, arg);
-- 
2.40.1