Re: [RFC PATCH v2 29/32] kvm: svm: Add support for SEV DEBUG_DECRYPT command

On 02/03/2017 16:18, Brijesh Singh wrote:

+static int __sev_dbg_decrypt_page(struct kvm *kvm, unsigned long src,
+		void *dst, int *error)
+{
+	inpages = sev_pin_memory(src, PAGE_SIZE, &npages);
+	if (!inpages) {
+		ret = -ENOMEM;
+		goto err_1;
+	}
+
+	data->handle = sev_get_handle(kvm);
+	data->dst_addr = __psp_pa(dst);
+	data->src_addr = __sev_page_pa(inpages[0]);
+	data->length = PAGE_SIZE;
+
+	ret = sev_issue_cmd(kvm, SEV_CMD_DBG_DECRYPT, data, error);
+	if (ret)
+		printk(KERN_ERR "SEV: DEBUG_DECRYPT %d (%#010x)\n",
+				ret, *error);
+	sev_unpin_memory(inpages, npages);
+err_1:
+	kfree(data);
+	return ret;
+}
+
+static int sev_dbg_decrypt(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	void *data;
+	int ret, offset, len;
+	struct kvm_sev_dbg debug;
+
+	if (!sev_guest(kvm))
+		return -ENOTTY;
+
+	if (copy_from_user(&debug, (void *)argp->data,
+				sizeof(struct kvm_sev_dbg)))
+		return -EFAULT;
+	/*
+	 * TODO: add support for decrypting length which crosses the
+	 * page boundary.
+	 */
+	offset = debug.src_addr & (PAGE_SIZE - 1);
+	if (offset + debug.length > PAGE_SIZE)
+		return -EINVAL;
+

Please do add it, it doesn't seem very different from what you're doing
in LAUNCH_UPDATE_DATA.  There's no need for a separate
__sev_dbg_decrypt_page function, you can just pin/unpin here and do a
per-page loop as in LAUNCH_UPDATE_DATA.

Paolo

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