[Qemu-devel] [RFC PATCH v1 05/10] KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command

["Singh, Brijesh" <brijesh.singh@amd.com>]

The command is used for copying the incoming buffer into the
SEV guest memory space.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 .../virtual/kvm/amd-memory-encryption.rst     | 24 ++++++
 arch/x86/kvm/svm.c                            | 84 +++++++++++++++++++
 include/uapi/linux/kvm.h                      |  9 ++
 3 files changed, 117 insertions(+)

diff --git a/Documentation/virtual/kvm/amd-memory-encryption.rst b/Documentation/virtual/kvm/amd-memory-encryption.rst
index acdff2454649..b9c3dc02f344 100644
--- a/Documentation/virtual/kvm/amd-memory-encryption.rst
+++ b/Documentation/virtual/kvm/amd-memory-encryption.rst
@@ -322,6 +322,30 @@ On success, the 'handle' field contains a new handle and on error, a negative va
 
 For more details, see SEV spec Section 6.12.
 
+14. KVM_SEV_RECEIVE_UPDATE_DATA
+----------------------------
+
+The KVM_SEV_RECEIVE_UPDATE_DATA command can be used by the hypervisor to copy
+the incoming buffers into the guest memory region with encryption context
+created during the KVM_SEV_RECEIVE_START.
+
+Parameters (in): struct kvm_sev_receive_update_data
+
+Returns: 0 on success, -negative on error
+
+::
+
+        struct kvm_sev_launch_receive_update_data {
+                __u64 hdr_uaddr;        /* userspace address containing the packet header */
+                __u32 hdr_len;
+
+                __u64 guest_uaddr;      /* the destination guest memory region */
+                __u32 guest_len;
+
+                __u64 trans_uaddr;      /* the incoming buffer memory region  */
+                __u32 trans_len;
+        };
+
 References
 ==========
 
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index a7dcf19baefb..c81cac09c5af 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7269,6 +7269,87 @@ static int sev_receive_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	return ret;
 }
 
+static int sev_receive_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	struct kvm_sev_receive_update_data params;
+	struct sev_data_receive_update_data *data;
+	void *hdr = NULL, *trans = NULL;
+	struct page **guest_page;
+	unsigned long n;
+	int ret, offset;
+
+	if (!sev_guest(kvm))
+		return -EINVAL;
+
+	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data,
+			sizeof(struct kvm_sev_receive_update_data)))
+		return -EFAULT;
+
+	if (!params.hdr_uaddr || !params.hdr_len ||
+	    !params.guest_uaddr || !params.guest_len ||
+	    !params.trans_uaddr || !params.trans_len)
+		return -EINVAL;
+
+	/* Check if we are crossing the page boundry */
+	offset = params.guest_uaddr & (PAGE_SIZE - 1);
+	if ((params.guest_len + offset > PAGE_SIZE))
+		return -EINVAL;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	hdr = psp_copy_user_blob(params.hdr_uaddr, params.hdr_len);
+	if (IS_ERR(hdr)) {
+		ret = PTR_ERR(hdr);
+		goto e_free;
+	}
+
+	data->hdr_address = __psp_pa(hdr);
+	data->hdr_len = params.hdr_len;
+
+	trans = psp_copy_user_blob(params.trans_uaddr, params.trans_len);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		goto e_free;
+	}
+
+	data->trans_address = __psp_pa(trans);
+	data->trans_len = params.trans_len;
+
+	/* Pin guest memory */
+	ret = -EFAULT;
+	guest_page = sev_pin_memory(kvm, params.guest_uaddr & PAGE_MASK,
+				    PAGE_SIZE, &n, 0);
+	if (!guest_page)
+		goto e_free;
+
+	data->guest_address = __sme_page_pa(guest_page[0]) + offset;
+	data->guest_len = params.guest_len;
+
+	/*
+	 * The RECEIVE_UPDATE_DATA command requires C-bit to be always set.
+	 * The __sme_page_pa() takes care of setting the C-bit only when SME
+	 * is enabled on the host. But we need to set the C-bit regarless of
+	 * the SME state.
+	 */
+	data->guest_address |= me_mask;
+
+	/* flush the caches to ensure that DRAM has recent contents */
+	sev_clflush_pages(guest_page, n);
+
+	data->handle = sev->handle;
+	ret = sev_issue_cmd(kvm, SEV_CMD_RECEIVE_UPDATE_DATA, data, &argp->error);
+
+	sev_unpin_memory(kvm, guest_page, n);
+e_free:
+	kfree(data);
+	kfree(hdr);
+	kfree(trans);
+	return ret;
+}
+
 static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 {
 	struct kvm_sev_cmd sev_cmd;
@@ -7322,6 +7403,9 @@ static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 	case KVM_SEV_RECEIVE_START:
 		r = sev_receive_start(kvm, &sev_cmd);
 		break;
+	case KVM_SEV_RECEIVE_UPDATE_DATA:
+		r = sev_receive_update_data(kvm, &sev_cmd);
+		break;
 	default:
 		r = -EINVAL;
 		goto out;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index fee75bf1fd90..07e058a3ec11 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1550,6 +1550,15 @@ struct kvm_sev_receive_start {
 	__u32 session_len;
 };
 
+struct kvm_sev_receive_update_data {
+	__u64 hdr_uaddr;
+	__u32 hdr_len;
+	__u64 guest_uaddr;
+	__u32 guest_len;
+	__u64 trans_uaddr;
+	__u32 trans_len;
+};
+
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
 #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
 #define KVM_DEV_ASSIGN_MASK_INTX	(1 << 2)
-- 
2.17.1