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Subject[RFC Part2 PATCH v3 21/26] KVM: SVM: Add support for SEV DEBUG_ENCRYPT command
Date
The command copies a plain text into guest memory and encrypts it using
the VM encryption key. The command will be used for debug purposes
(e.g setting breakpoint through gdbserver)

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/kvm/svm.c | 174 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 174 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 933384a..75dcaa9 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -6214,6 +6214,176 @@ static int sev_dbg_decrypt(struct kvm *kvm, struct kvm_sev_cmd *argp)
return ret;
}

+static int __sev_dbg_enc(struct kvm *kvm, unsigned long __user vaddr,
+ unsigned long paddr, unsigned long __user dst_vaddr,
+ unsigned long dst_paddr, int size, int *error)
+{
+ struct page *src_tpage = NULL;
+ struct page *dst_tpage = NULL;
+ int ret, len = size;
+
+ /*
+ * Debug encrypt command works with 16-byte aligned inputs. Function
+ * handles the alingment issue as below:
+ *
+ * case 1
+ * If source buffer is not 16-byte aligned then we copy the data from
+ * source buffer into a PAGE aligned intermediate (src_tpage) buffer
+ * and use this intermediate buffer as source buffer
+ *
+ * case 2
+ * If destination buffer or length is not 16-byte aligned then:
+ * - decrypt portion of destination buffer into intermediate buffer
+ * (dst_tpage)
+ * - copy the source data into intermediate buffer
+ * - use the intermediate buffer as source buffer
+ */
+
+ /* If source is not aligned (case 1) */
+ if (!IS_ALIGNED(vaddr, 16)) {
+ src_tpage = alloc_page(GFP_KERNEL);
+ if (!src_tpage)
+ return -ENOMEM;
+
+ if (copy_from_user(page_address(src_tpage),
+ (uint8_t *)vaddr, size)) {
+ __free_page(src_tpage);
+ return -EFAULT;
+ }
+ paddr = __sme_page_pa(src_tpage);
+
+ /* flush the caches to ensure that DRAM has recent contents */
+ clflush_cache_range(page_address(src_tpage), PAGE_SIZE);
+ }
+
+ /* If destination buffer or length is not aligned (case 2) */
+ 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;
+ }
+
+ /* decrypt destination buffer into intermediate buffer */
+ ret = __sev_dbg_dec(kvm,
+ round_down(dst_paddr, 16),
+ 0,
+ (unsigned long)page_address(dst_tpage),
+ __sme_page_pa(dst_tpage),
+ round_up(size, 16),
+ error);
+ if (ret)
+ goto e_free;
+
+ dst_offset = dst_paddr & 15;
+
+ /*
+ * modify the intermediate buffer with data from source
+ * buffer.
+ */
+ 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 *) vaddr, size)) {
+ ret = -EFAULT;
+ goto e_free;
+ }
+ }
+
+
+ /* use intermediate buffer as source */
+ paddr = __sme_page_pa(dst_tpage);
+
+ /* flush the caches to ensure that DRAM gets recent updates */
+ clflush_cache_range(page_address(dst_tpage), PAGE_SIZE);
+
+ /* now we have length and destination buffer aligned */
+ dst_paddr = round_down(dst_paddr, 16);
+ len = round_up(size, 16);
+ }
+
+ ret = __sev_dbg_enc_dec(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_encrypt(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+ unsigned long vaddr, vaddr_end, dst_vaddr, next_vaddr;
+ struct kvm_sev_dbg debug;
+ int ret, size;
+
+ if (!sev_guest(kvm))
+ return -ENOTTY;
+
+ if (copy_from_user(&debug, (void *)argp->data,
+ sizeof(struct kvm_sev_dbg)))
+ return -EFAULT;
+
+ size = debug.length;
+ vaddr = debug.src_addr;
+ vaddr_end = vaddr + size;
+ dst_vaddr = debug.dst_addr;
+
+ for (; vaddr < vaddr_end; vaddr = next_vaddr) {
+ unsigned long n;
+ int s_off, d_off, len;
+ struct page **srcpage, **dstpage;
+
+ /* lock the user memory */
+ srcpage = sev_pin_memory(vaddr & PAGE_MASK, PAGE_SIZE, &n, 0);
+ if (!srcpage)
+ return -EFAULT;
+
+ dstpage = sev_pin_memory(dst_vaddr & PAGE_MASK, PAGE_SIZE,
+ &n, 1);
+ if (!dstpage) {
+ sev_unpin_memory(srcpage, n);
+ return -EFAULT;
+ }
+
+ /* flush the caches to ensure that DRAM has recent contents */
+ sev_clflush_pages(srcpage, 1);
+ sev_clflush_pages(dstpage, 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_enc(kvm,
+ vaddr,
+ __sme_page_pa(srcpage[0]) + s_off,
+ dst_vaddr,
+ __sme_page_pa(dstpage[0]) + d_off,
+ len, &argp->error);
+
+ /* unlock the user memory */
+ sev_unpin_memory(srcpage, 1);
+ sev_unpin_memory(dstpage, 1);
+
+ if (ret)
+ goto err;
+
+ next_vaddr = vaddr + len;
+ dst_vaddr = dst_vaddr + len;
+ size -= len;
+ }
+err:
+ return ret;
+}
+
static int svm_memory_encryption_op(struct kvm *kvm, void __user *argp)
{
struct kvm_sev_cmd sev_cmd;
@@ -6253,6 +6423,10 @@ static int svm_memory_encryption_op(struct kvm *kvm, void __user *argp)
r = sev_dbg_decrypt(kvm, &sev_cmd);
break;
}
+ case KVM_SEV_DBG_ENCRYPT: {
+ r = sev_dbg_encrypt(kvm, &sev_cmd);
+ break;
+ }
default:
break;
}
--
2.9.4
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