[Part2 PATCH v9 33/38] KVM: SVM: Add support for SEV DEBUG_ENCRYPT command

Brijesh Singh
2017-12-05T01:08:17Z

The command copies a plaintext into guest memory and encrypts it using
the VM encryption key. The command will be used for debug purposes
(e.g setting breakpoints through gdbserver)

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>
---
arch/x86/kvm/svm.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 93 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ec2b864faec2..11d4860997d9 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -6240,6 +6240,83 @@ static int __sev_dbg_decrypt_user(struct kvm *kvm, unsigned long paddr,
return ret;
}

+static int __sev_dbg_encrypt_user(struct kvm *kvm, unsigned long paddr,
+ unsigned long __user vaddr,
+ unsigned long dst_paddr,
+ unsigned long __user dst_vaddr,
+ int size, int *error)
+{
+ struct page *src_tpage = NULL;
+ struct page *dst_tpage = NULL;
+ int ret, len = size;
+
+ /* If source buffer is not aligned then use an intermediate buffer */
+ if (!IS_ALIGNED(vaddr, 16)) {
+ src_tpage = alloc_page(GFP_KERNEL);
+ if (!src_tpage)
+ return -ENOMEM;
+
+ if (copy_from_user(page_address(src_tpage),
+ (void __user *)(uintptr_t)vaddr, size)) {
+ __free_page(src_tpage);
+ return -EFAULT;
+ }
+
+ paddr = __sme_page_pa(src_tpage);
+ }
+
+ /*
+ * If destination buffer or length is not aligned then do read-modify-write:
+ * - decrypt destination in an intermediate buffer
+ * - copy the source buffer in an intermediate buffer
+ * - use the intermediate buffer as source buffer
+ */
+ if (!IS_ALIGNED(dst_vaddr, 16) || !IS_ALIGNED(size, 16)) {
+ int dst_offset;
+
+ dst_tpage = alloc_page(GFP_KERNEL);
+ if (!dst_tpage) {
+ ret = -ENOMEM;
+ goto e_free;
+ }
+
+ ret = __sev_dbg_decrypt(kvm, dst_paddr,
+ __sme_page_pa(dst_tpage), size, error);
+ if (ret)
+ goto e_free;
+
+ /*
+ * If source is kernel buffer then use memcpy() otherwise
+ * copy_from_user().
+ */
+ dst_offset = dst_paddr & 15;
+
+ if (src_tpage)
+ memcpy(page_address(dst_tpage) + dst_offset,
+ page_address(src_tpage), size);
+ else {
+ if (copy_from_user(page_address(dst_tpage) + dst_offset,
+ (void __user *)(uintptr_t)vaddr, size)) {
+ ret = -EFAULT;
+ goto e_free;
+ }
+ }
+
+ paddr = __sme_page_pa(dst_tpage);
+ dst_paddr = round_down(dst_paddr, 16);
+ len = round_up(size, 16);
+ }
+
+ ret = __sev_issue_dbg_cmd(kvm, paddr, dst_paddr, len, error, true);
+
+e_free:
+ if (src_tpage)
+ __free_page(src_tpage);
+ if (dst_tpage)
+ __free_page(dst_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;
@@ -6292,11 +6369,19 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
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);
+ if (dec)
+ 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);
+ else
+ ret = __sev_dbg_encrypt_user(kvm,
+ __sme_page_pa(src_p[0]) + s_off,
+ vaddr,
+ __sme_page_pa(dst_p[0]) + d_off,
+ dst_vaddr,
+ len, &argp->error);

sev_unpin_memory(kvm, src_p, 1);
sev_unpin_memory(kvm, dst_p, 1);
@@ -6347,6 +6432,9 @@ static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
case KVM_SEV_DBG_DECRYPT:
r = sev_dbg_crypt(kvm, &sev_cmd, true);
break;
+ case KVM_SEV_DBG_ENCRYPT:
+ r = sev_dbg_crypt(kvm, &sev_cmd, false);
+ break;
default:
r = -EINVAL;
goto out;
--
2.9.5