[PATCH Part2 RFC v4 24/40] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_UPDATE command

From: Brijesh Singh
Date: Wed Jul 07 2021 - 14:38:23 EST

The KVM_SEV_SNP_LAUNCH_UPDATE command can be used to insert data into the
guest's memory. The data is encrypted with the cryptographic context
created with the KVM_SEV_SNP_LAUNCH_START.

In addition to the inserting data, it can insert a two special pages
into the guests memory: the secrets page and the CPUID page.

For more information see the SEV-SNP specification.

Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
.../virt/kvm/amd-memory-encryption.rst | 28 ++++
arch/x86/kvm/svm/sev.c | 142 ++++++++++++++++++
include/linux/sev.h | 2 +
include/uapi/linux/kvm.h | 18 +++
4 files changed, 190 insertions(+)

diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
index 8620383d405a..60ace54438c3 100644
--- a/Documentation/virt/kvm/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/amd-memory-encryption.rst
@@ -468,6 +468,34 @@ Returns: 0 on success, -negative on error

See the SEV-SNP specification for further detail on the launch input.

+20. KVM_SNP_LAUNCH_UPDATE
+-------------------------
+
+The KVM_SNP_LAUNCH_UPDATE is used for encrypting a memory region. It also
+calculates a measurement of the memory contents. The measurement is a signature
+of the memory contents that can be sent to the guest owner as an attestation
+that the memory was encrypted correctly by the firmware.
+
+Parameters (in): struct kvm_snp_launch_update
+
+Returns: 0 on success, -negative on error
+
+::
+
+ struct kvm_sev_snp_launch_update {
+ __u64 uaddr; /* userspace address need to be encrypted */
+ __u32 len; /* length of memory region */
+ __u8 imi_page; /* 1 if memory is part of the IMI */
+ __u8 page_type; /* page type */
+ __u8 vmpl3_perms; /* VMPL3 permission mask */
+ __u8 vmpl2_perms; /* VMPL2 permission mask */
+ __u8 vmpl1_perms; /* VMPL1 permission mask */
+ };
+
+See the SEV-SNP spec for further details on how to build the VMPL permission
+mask and page type.
+
+
References
==========

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index f44a657e8912..1f0635ac9ff9 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -17,6 +17,7 @@
#include <linux/misc_cgroup.h>
#include <linux/processor.h>
#include <linux/trace_events.h>
+#include <linux/sev.h>
#include <asm/fpu/internal.h>

#include <asm/trapnr.h>
@@ -1624,6 +1625,144 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
return rc;
}

+static struct kvm_memory_slot *hva_to_memslot(struct kvm *kvm, unsigned long hva)
+{
+ struct kvm_memslots *slots = kvm_memslots(kvm);
+ struct kvm_memory_slot *memslot;
+
+ kvm_for_each_memslot(memslot, slots) {
+ if (hva >= memslot->userspace_addr &&
+ hva < memslot->userspace_addr + (memslot->npages << PAGE_SHIFT))
+ return memslot;
+ }
+
+ return NULL;
+}
+
+static bool hva_to_gpa(struct kvm *kvm, unsigned long hva, gpa_t *gpa)
+{
+ struct kvm_memory_slot *memslot;
+ gpa_t gpa_offset;
+
+ memslot = hva_to_memslot(kvm, hva);
+ if (!memslot)
+ return false;
+
+ gpa_offset = hva - memslot->userspace_addr;
+ *gpa = ((memslot->base_gfn << PAGE_SHIFT) + gpa_offset);
+
+ return true;
+}
+
+static int snp_page_reclaim(struct page *page, int rmppage_size)
+{
+ struct sev_data_snp_page_reclaim data = {};
+ struct rmpupdate e = {};
+ int rc, err;
+
+ data.paddr = __sme_page_pa(page) | rmppage_size;
+ rc = snp_guest_page_reclaim(&data, &err);
+ if (rc)
+ return rc;
+
+ return rmpupdate(page, &e);
+}
+
+static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+ unsigned long npages, vaddr, vaddr_end, i, next_vaddr;
+ struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+ struct sev_data_snp_launch_update data = {};
+ struct kvm_sev_snp_launch_update params;
+ int *error = &argp->error;
+ struct kvm_vcpu *vcpu;
+ struct page **inpages;
+ struct rmpupdate e;
+ int ret;
+
+ if (!sev_snp_guest(kvm))
+ return -ENOTTY;
+
+ if (!sev->snp_context)
+ return -EINVAL;
+
+ if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
+ return -EFAULT;
+
+ data.gctx_paddr = __psp_pa(sev->snp_context);
+
+ /* Lock the user memory. */
+ inpages = sev_pin_memory(kvm, params.uaddr, params.len, &npages, 1);
+ if (!inpages)
+ return -ENOMEM;
+
+ vcpu = kvm_get_vcpu(kvm, 0);
+ vaddr = params.uaddr;
+ vaddr_end = vaddr + params.len;
+
+ for (i = 0; vaddr < vaddr_end; vaddr = next_vaddr, i++) {
+ unsigned long psize, pmask;
+ int level = PG_LEVEL_4K;
+ gpa_t gpa;
+
+ if (!hva_to_gpa(kvm, vaddr, &gpa)) {
+ ret = -EINVAL;
+ goto e_unpin;
+ }
+
+ psize = page_level_size(level);
+ pmask = page_level_mask(level);
+ gpa = gpa & pmask;
+
+ /* Transition the page state to pre-guest */
+ memset(&e, 0, sizeof(e));
+ e.assigned = 1;
+ e.gpa = gpa;
+ e.asid = sev_get_asid(kvm);
+ e.immutable = true;
+ e.pagesize = X86_TO_RMP_PG_LEVEL(level);
+ ret = rmpupdate(inpages[i], &e);
+ if (ret) {
+ ret = -EFAULT;
+ goto e_unpin;
+ }
+
+ data.address = __sme_page_pa(inpages[i]);
+ data.page_size = e.pagesize;
+ data.page_type = params.page_type;
+ data.vmpl3_perms = params.vmpl3_perms;
+ data.vmpl2_perms = params.vmpl2_perms;
+ data.vmpl1_perms = params.vmpl1_perms;
+ ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE, &data, error);
+ if (ret) {
+ snp_page_reclaim(inpages[i], e.pagesize);
+ goto e_unpin;
+ }
+
+ next_vaddr = (vaddr & pmask) + psize;
+ }
+
+e_unpin:
+ /* Content of memory is updated, mark pages dirty */
+ memset(&e, 0, sizeof(e));
+ for (i = 0; i < npages; i++) {
+ set_page_dirty_lock(inpages[i]);
+ mark_page_accessed(inpages[i]);
+
+ /*
+ * If its an error, then update RMP entry to change page ownership
+ * to the hypervisor.
+ */
+ if (ret)
+ rmpupdate(inpages[i], &e);
+ }
+
+ /* Unlock the user pages */
+ sev_unpin_memory(kvm, inpages, npages);
+
+ return ret;
+}
+
int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
{
struct kvm_sev_cmd sev_cmd;
@@ -1716,6 +1855,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
case KVM_SEV_SNP_LAUNCH_START:
r = snp_launch_start(kvm, &sev_cmd);
break;
+ case KVM_SEV_SNP_LAUNCH_UPDATE:
+ r = snp_launch_update(kvm, &sev_cmd);
+ break;
default:
r = -EINVAL;
goto out;
diff --git a/include/linux/sev.h b/include/linux/sev.h
index bcd4d75d87c8..82e804a2ee0d 100644
--- a/include/linux/sev.h
+++ b/include/linux/sev.h
@@ -36,8 +36,10 @@ struct __packed rmpentry {

/* RMP page size */
#define RMP_PG_SIZE_4K 0
+#define RMP_PG_SIZE_2M 1

#define RMP_TO_X86_PG_LEVEL(level) (((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M)
+#define X86_TO_RMP_PG_LEVEL(level) (((level) == PG_LEVEL_4K) ? RMP_PG_SIZE_4K : RMP_PG_SIZE_2M)

struct rmpupdate {
u64 gpa;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index dbd05179d8fa..c9b453fb31d4 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1681,6 +1681,7 @@ enum sev_cmd_id {
/* SNP specific commands */
KVM_SEV_SNP_INIT = 256,
KVM_SEV_SNP_LAUNCH_START,
+ KVM_SEV_SNP_LAUNCH_UPDATE,

KVM_SEV_NR_MAX,
};
@@ -1790,6 +1791,23 @@ struct kvm_sev_snp_launch_start {
__u8 gosvw[16];
};

+#define KVM_SEV_SNP_PAGE_TYPE_NORMAL 0x1
+#define KVM_SEV_SNP_PAGE_TYPE_VMSA 0x2
+#define KVM_SEV_SNP_PAGE_TYPE_ZERO 0x3
+#define KVM_SEV_SNP_PAGE_TYPE_UNMEASURED 0x4
+#define KVM_SEV_SNP_PAGE_TYPE_SECRETS 0x5
+#define KVM_SEV_SNP_PAGE_TYPE_CPUID 0x6
+
+struct kvm_sev_snp_launch_update {
+ __u64 uaddr;
+ __u32 len;
+ __u8 imi_page;
+ __u8 page_type;
+ __u8 vmpl3_perms;
+ __u8 vmpl2_perms;
+ __u8 vmpl1_perms;
+};
+
#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