virt/coco/sev-guest: Convert the sw_exit_info_2 checking to a switch-case

commit fa4ae42cc60a7dea30e8f2db444b808d80862345 upstream.

snp_issue_guest_request() checks the value returned by the hypervisor in
sw_exit_info_2 and returns a different error depending on it.

Convert those checks into a switch-case to make it more readable when
more error values are going to be checked in the future.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20230307192449.24732-8-bp@alien8.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 5dc9c53..55df10e 100644 (file)
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2210,15 +2210,21 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
                goto e_put;
 
        *fw_err = ghcb->save.sw_exit_info_2;
-       if (ghcb->save.sw_exit_info_2) {
+       switch (*fw_err) {
+       case 0:
+               break;
+
+       case SNP_GUEST_REQ_INVALID_LEN:
                /* Number of expected pages are returned in RBX */
-               if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST &&
-                   ghcb->save.sw_exit_info_2 == SNP_GUEST_REQ_INVALID_LEN) {
+               if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST) {
                        input->data_npages = ghcb_get_rbx(ghcb);
                        ret = -ENOSPC;
-               } else {
-                       ret = -EIO;
+                       break;
                }
+               fallthrough;
+       default:
+               ret = -EIO;
+               break;
        }
 
 e_put: