[tip: x86/seves] x86/sev-es: Remove subtraction of res variable

[tip-bot2 for Borislav Petkov]

The following commit has been merged into the x86/seves branch of tip:

Commit-ID:     bb8dc26937d51b3421b26d9d91cdad3484c34b7e
Gitweb:        https://git.kernel.org/tip/bb8dc26937d51b3421b26d9d91cdad3484c34b7e
Author:        Borislav Petkov <bp@xxxxxxx>
AuthorDate:    Tue, 23 Feb 2021 12:03:19 +01:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Mon, 01 Mar 2021 12:40:22 +01:00

x86/sev-es: Remove subtraction of res variable

vc_decode_insn() calls copy_from_kernel_nofault() by way of
vc_fetch_insn_kernel() to fetch 15 bytes max of opcodes to decode.

copy_from_kernel_nofault() returns negative on error and 0 on success.
The error case is handled by returning ES_EXCEPTION.

In the success case, the ret variable which contains the return value is
0 so there's no need to subtract it from MAX_INSN_SIZE when initializing
the insn buffer for further decoding. Remove it.

No functional changes.

Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Joerg Roedel <jroedel@xxxxxxx>
Link: https://lkml.kernel.org/r/20210223111130.16201-1-bp@xxxxxxxxx
---
 arch/x86/kernel/sev-es.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 84c1821..1e78f4b 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -267,7 +267,7 @@ static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
 			return ES_EXCEPTION;
 		}
 
-		insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE - res, 1);
+		insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE, 1);
 		insn_get_length(&ctxt->insn);
 	}