[RFC PATCH v1 02/10] KVM: SVM: Add KVM_SEND_UPDATE_DATA command

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

The command is used for encrypting the guest memory region using the encryption
context created with KVM_SEV_SEND_START.

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     |  23 ++++
 arch/x86/kvm/svm.c                            | 128 +++++++++++++++++-
 include/uapi/linux/kvm.h                      |   9 ++
 3 files changed, 157 insertions(+), 3 deletions(-)

diff --git a/Documentation/virtual/kvm/amd-memory-encryption.rst b/Documentation/virtual/kvm/amd-memory-encryption.rst
index 340ac4f87321..a0208e171489 100644
--- a/Documentation/virtual/kvm/amd-memory-encryption.rst
+++ b/Documentation/virtual/kvm/amd-memory-encryption.rst
@@ -262,6 +262,29 @@ Returns: 0 on success, -negative on error
                 __u32 amd_cert_len;
         };
 
+11. KVM_SEV_SEND_UPDATE_DATA
+----------------------------
+
+The KVM_SEV_SEND_UPDATE_DATA command can be used by the hypervisor to encrypt the
+outgoing guest memory region with encryption context creating using KVM_SEV_SEND_START.
+
+Parameters (in): struct kvm_sev_send_update_data
+
+Returns: 0 on success, -negative on error
+
+::
+
+        struct kvm_sev_launch_send_update_data {
+                __u64 hdr_uaddr;        /* userspace address containing the packet header */
+                __u32 hdr_len;
+
+                __u64 guest_uaddr;      /* the source memory region to be encrypted */
+                __u32 guest_len;
+
+                __u64 trans_uaddr;      /* the destition memory region  */
+                __u32 trans_len;
+        };
+
 References
 ==========
 
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 4c2a225ba546..a1cfd36d6195 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -418,6 +418,7 @@ enum {
 
 static unsigned int max_sev_asid;
 static unsigned int min_sev_asid;
+static unsigned long me_mask;
 static unsigned long *sev_asid_bitmap;
 #define __sme_page_pa(x) __sme_set(page_to_pfn(x) << PAGE_SHIFT)
 
@@ -1216,15 +1217,21 @@ static int avic_ga_log_notifier(u32 ga_tag)
 static __init int sev_hardware_setup(void)
 {
 	struct sev_user_data_status *status;
+	int eax, ebx;
 	int rc;
 
-	/* Maximum number of encrypted guests supported simultaneously */
-	max_sev_asid = cpuid_ecx(0x8000001F);
+	/*
+	 * Query the memory encryption information.
+	 *  EBX:  Bit 0:5 Pagetable bit position used to indicate encryption (aka Cbit).
+	 *  ECX:  Maximum number of encrypted guests supported simultaneously.
+	 *  EDX:  Minimum ASID value that should be used for SEV guest.
+	 */
+	cpuid(0x8000001f, &eax, &ebx, &max_sev_asid, &min_sev_asid);
 
 	if (!max_sev_asid)
 		return 1;
 
-	/* Minimum ASID value that should be used for SEV guest */
+	me_mask = 1UL << (ebx & 0x3f);
 	min_sev_asid = cpuid_edx(0x8000001F);
 
 	/* Initialize SEV ASID bitmap */
@@ -7053,6 +7060,118 @@ static int sev_send_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	return ret;
 }
 
+static int sev_send_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	struct sev_data_send_update_data *data;
+	struct kvm_sev_send_update_data params;
+	void *hdr = NULL, *trans_data = NULL;
+	struct page **guest_page = NULL;
+	unsigned long n;
+	int ret, offset;
+
+	if (!sev_guest(kvm))
+		return -ENOTTY;
+
+	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data,
+			sizeof(struct kvm_sev_send_update_data)))
+		return -EFAULT;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	/* userspace wants to query either header or trans length */
+	if (!params.trans_len || !params.hdr_len)
+		goto cmd;
+
+	ret = -EINVAL;
+	if (!params.trans_uaddr || !params.guest_uaddr ||
+	    !params.guest_len || !params.hdr_uaddr)
+		goto e_free;
+
+	/* Check if we are crossing the page boundry */
+	ret = -EINVAL;
+	offset = params.guest_uaddr & (PAGE_SIZE - 1);
+	if ((params.guest_len + offset > PAGE_SIZE))
+		goto e_free;
+
+	ret = -ENOMEM;
+	hdr = kmalloc(params.hdr_len, GFP_KERNEL);
+	if (!hdr)
+		goto e_free;
+
+	data->hdr_address = __psp_pa(hdr);
+	data->hdr_len = params.hdr_len;
+
+	ret = -ENOMEM;
+	trans_data = kmalloc(params.trans_len, GFP_KERNEL);
+	if (!trans_data)
+		goto e_free;
+
+	data->trans_address = __psp_pa(trans_data);
+	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 SEND_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, 1);
+
+cmd:
+	data->handle = sev->handle;
+	ret = sev_issue_cmd(kvm, SEV_CMD_SEND_UPDATE_DATA, data, &argp->error);
+
+	/* userspace asked for header or trans length and FW responded with data */
+	if (!params.trans_len || !params.hdr_len) {
+		params.hdr_len = data->hdr_len;
+		params.trans_len = data->trans_len;
+		goto done;
+	}
+
+	if (ret)
+		goto e_unpin;
+
+	/* copy transport buffer to user space */
+	if (copy_to_user((void __user *)(uintptr_t)params.trans_uaddr,
+			 trans_data, params.trans_len)) {
+		ret = -EFAULT;
+		goto e_unpin;
+	}
+
+	/* copy packet header to userspace */
+	if (copy_to_user((void __user *)(uintptr_t)params.hdr_uaddr, hdr, params.hdr_len))
+		ret = -EFAULT;
+
+e_unpin:
+	sev_unpin_memory(kvm, guest_page, n);
+done:
+	if (copy_to_user((void __user *)(uintptr_t)argp->data, &params,
+			sizeof(struct kvm_sev_send_update_data)))
+		ret = -EFAULT;
+e_free:
+	kfree(data);
+	kfree(trans_data);
+	kfree(hdr);
+
+	return ret;
+}
+
 static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 {
 	struct kvm_sev_cmd sev_cmd;
@@ -7097,6 +7216,9 @@ static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 	case KVM_SEV_SEND_START:
 		r = sev_send_start(kvm, &sev_cmd);
 		break;
+	case KVM_SEV_SEND_UPDATE_DATA:
+		r = sev_send_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 f425418bec13..0bee91bba329 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1532,6 +1532,15 @@ struct kvm_sev_send_start {
 	__u32 session_len;
 };
 
+struct kvm_sev_send_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