[PATCH v4 4/9] mshv: add SEV-SNP PSP request hypercall

[Wei Hu <weh@linux.microsoft.com>]

From: Wei Liu <wei.liu@kernel.org>

Add a helper for HVCALL_ISSUE_SNP_PSP_GUEST_REQUEST so MSHV can issue
asynchronous PSP guest requests on behalf of encrypted partitions.

Signed-off-by: Wei Liu <wei.liu@kernel.org>
---
 drivers/hv/mshv_root.h         |  8 +++++++
 drivers/hv/mshv_root_hv_call.c | 41 ++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
index a1059b578a39..2150019b588c 100644
--- a/drivers/hv/mshv_root.h
+++ b/drivers/hv/mshv_root.h
@@ -388,4 +388,12 @@ bool mshv_region_handle_gfn_fault(struct mshv_mem_region *region, u64 gfn);
 void mshv_region_movable_fini(struct mshv_mem_region *region);
 bool mshv_region_movable_init(struct mshv_mem_region *region);
 
+#ifdef HV_SUPPORTS_SEV_SNP_GUESTS
+int hv_call_issue_psp_guest_request(u64 partition_id, u64 req_pfn,
+				    u64 rsp_pfn,
+				    void (*completion_handler)(void *data,
+							       u64 *status),
+				    void *completion_data);
+#endif
+
 #endif /* _MSHV_ROOT_H_ */
diff --git a/drivers/hv/mshv_root_hv_call.c b/drivers/hv/mshv_root_hv_call.c
index 1fa644e0e437..fca2419df397 100644
--- a/drivers/hv/mshv_root_hv_call.c
+++ b/drivers/hv/mshv_root_hv_call.c
@@ -1040,6 +1040,47 @@ int hv_unmap_stats_page(enum hv_stats_object_type type,
 	return ret;
 }
 
+#ifdef HV_SUPPORTS_SEV_SNP_GUESTS
+int hv_call_issue_psp_guest_request(u64 partition_id, u64 req_pfn,
+				    u64 rsp_pfn,
+				    void (*completion_handler)(void *data,
+							       u64 *status),
+				    void *completion_data)
+{
+	struct hv_input_issue_psp_guest_request *input;
+	unsigned long flags;
+	u64 status;
+
+	if (!completion_handler) {
+		pr_err("%s: missing completion handler\n", __func__);
+		return -EINVAL;
+	}
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+	input->partition_id = partition_id;
+	input->request_page = req_pfn;
+	input->response_page = rsp_pfn;
+	status = hv_do_hypercall(HVCALL_ISSUE_SNP_PSP_GUEST_REQUEST, input,
+				 NULL);
+	local_irq_restore(flags);
+
+	/* Hyper-V consumes the input before returning CALL_PENDING. */
+	if (hv_result(status) == HV_STATUS_CALL_PENDING)
+		completion_handler(completion_data, &status);
+
+	if (!hv_result_success(status)) {
+		pr_err_ratelimited("%s: status=%s partition_id=%llu\n",
+				   __func__, hv_result_to_string(status),
+				   partition_id);
+		return hv_result_to_errno(status);
+	}
+
+	return 0;
+}
+#endif
+
 int hv_call_modify_spa_host_access(u64 partition_id, struct page **pages,
 				   u64 page_struct_count, u32 host_access,
 				   u32 flags, u8 acquire)
-- 
2.43.0