[Part2 PATCH v9 32/38] KVM: SVM: Add support for SEV DEBUG_DECRYPT command

Brijesh Singh
2017-12-05T01:08:39Z

The command is used for decrypting a guest memory region for debug
purposes.

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>
Reviewed-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kvm/svm.c | 152 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 152 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index f5da2753790d..ec2b864faec2 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -6163,6 +6163,155 @@ static int sev_guest_status(struct kvm *kvm, struct kvm_sev_cmd *argp)
return ret;
}

+static int __sev_issue_dbg_cmd(struct kvm *kvm, unsigned long src,
+ unsigned long dst, int size,
+ int *error, bool enc)
+{
+ struct kvm_sev_info *sev = &kvm->arch.sev_info;
+ struct sev_data_dbg *data;
+ int ret;
+
+ data = kzalloc(sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ data->handle = sev->handle;
+ data->dst_addr = dst;
+ data->src_addr = src;
+ data->len = size;
+
+ ret = sev_issue_cmd(kvm,
+ enc ? SEV_CMD_DBG_ENCRYPT : SEV_CMD_DBG_DECRYPT,
+ data, error);
+ kfree(data);
+ return ret;
+}
+
+static int __sev_dbg_decrypt(struct kvm *kvm, unsigned long src_paddr,
+ unsigned long dst_paddr, int sz, int *err)
+{
+ int offset;
+
+ /*
+ * Its safe to read more than we are asked, caller should ensure that
+ * destination has enough space.
+ */
+ src_paddr = round_down(src_paddr, 16);
+ offset = src_paddr & 15;
+ sz = round_up(sz + offset, 16);
+
+ return __sev_issue_dbg_cmd(kvm, src_paddr, dst_paddr, sz, err, false);
+}
+
+static int __sev_dbg_decrypt_user(struct kvm *kvm, unsigned long paddr,
+ unsigned long __user dst_uaddr,
+ unsigned long dst_paddr,
+ int size, int *err)
+{
+ struct page *tpage = NULL;
+ int ret, offset;
+
+ /* if inputs are not 16-byte then use intermediate buffer */
+ if (!IS_ALIGNED(dst_paddr, 16) ||
+ !IS_ALIGNED(paddr, 16) ||
+ !IS_ALIGNED(size, 16)) {
+ tpage = (void *)alloc_page(GFP_KERNEL);
+ if (!tpage)
+ return -ENOMEM;
+
+ dst_paddr = __sme_page_pa(tpage);
+ }
+
+ ret = __sev_dbg_decrypt(kvm, paddr, dst_paddr, size, err);
+ if (ret)
+ goto e_free;
+
+ if (tpage) {
+ offset = paddr & 15;
+ if (copy_to_user((void __user *)(uintptr_t)dst_uaddr,
+ page_address(tpage) + offset, size))
+ ret = -EFAULT;
+ }
+
+e_free:
+ if (tpage)
+ __free_page(tpage);
+
+ return ret;
+}
+
+static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
+{
+ unsigned long vaddr, vaddr_end, next_vaddr;
+ unsigned long dst_vaddr, dst_vaddr_end;
+ struct page **src_p, **dst_p;
+ struct kvm_sev_dbg debug;
+ unsigned long n;
+ int ret, size;
+
+ if (!sev_guest(kvm))
+ return -ENOTTY;
+
+ if (copy_from_user(&debug, (void __user *)(uintptr_t)argp->data, sizeof(debug)))
+ return -EFAULT;
+
+ vaddr = debug.src_uaddr;
+ size = debug.len;
+ vaddr_end = vaddr + size;
+ dst_vaddr = debug.dst_uaddr;
+ dst_vaddr_end = dst_vaddr + size;
+
+ for (; vaddr < vaddr_end; vaddr = next_vaddr) {
+ int len, s_off, d_off;
+
+ /* lock userspace source and destination page */
+ src_p = sev_pin_memory(kvm, vaddr & PAGE_MASK, PAGE_SIZE, &n, 0);
+ if (!src_p)
+ return -EFAULT;
+
+ dst_p = sev_pin_memory(kvm, dst_vaddr & PAGE_MASK, PAGE_SIZE, &n, 1);
+ if (!dst_p) {
+ sev_unpin_memory(kvm, src_p, n);
+ return -EFAULT;
+ }
+
+ /*
+ * The DBG_{DE,EN}CRYPT commands will perform {dec,en}cryption of the
+ * memory content (i.e it will write the same memory region with C=1).
+ * It's possible that the cache may contain the data with C=0, i.e.,
+ * unencrypted so invalidate it first.
+ */
+ sev_clflush_pages(src_p, 1);
+ sev_clflush_pages(dst_p, 1);
+
+ /*
+ * Since user buffer may not be page aligned, calculate the
+ * offset within the page.
+ */
+ s_off = vaddr & ~PAGE_MASK;
+ d_off = dst_vaddr & ~PAGE_MASK;
+ len = min_t(size_t, (PAGE_SIZE - s_off), size);
+
+ ret = __sev_dbg_decrypt_user(kvm,
+ __sme_page_pa(src_p[0]) + s_off,
+ dst_vaddr,
+ __sme_page_pa(dst_p[0]) + d_off,
+ len, &argp->error);
+
+ sev_unpin_memory(kvm, src_p, 1);
+ sev_unpin_memory(kvm, dst_p, 1);
+
+ if (ret)
+ goto err;
+
+ next_vaddr = vaddr + len;
+ dst_vaddr = dst_vaddr + len;
+ size -= len;
+ }
+err:
+ return ret;
+}
+
static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
{
struct kvm_sev_cmd sev_cmd;
@@ -6195,6 +6344,9 @@ static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
case KVM_SEV_GUEST_STATUS:
r = sev_guest_status(kvm, &sev_cmd);
break;
+ case KVM_SEV_DBG_DECRYPT:
+ r = sev_dbg_crypt(kvm, &sev_cmd, true);
+ break;
default:
r = -EINVAL;
goto out;
--
2.9.5