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

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

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

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@suse.de>
---
 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 84c1821819af..1e78f4bd7bf2 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);
 	}
 
-- 
2.29.2

Re: [PATCH] x86/sev-es: Remove subtraction of res variable

[Joerg Roedel]

On Tue, Feb 23, 2021 at 12:11:30PM +0100, Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.de>
> 
> 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@suse.de>

Reviewed-by: Joerg Roedel <jroedel@suse.de>

> ---
>  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 84c1821819af..1e78f4bd7bf2 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);
>  	}
>  
> -- 
> 2.29.2

[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@suse.de>
AuthorDate:    Tue, 23 Feb 2021 12:03:19 +01:00
Committer:     Borislav Petkov <bp@suse.de>
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@suse.de>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Link: https://lkml.kernel.org/r/20210223111130.16201-1-bp@alien8.de
---
 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);
 	}
 

[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:     f3db3365c069c2a8505cdee8033fe3d22d2fe6c0
Gitweb:        https://git.kernel.org/tip/f3db3365c069c2a8505cdee8033fe3d22d2fe6c0
Author:        Borislav Petkov <bp@suse.de>
AuthorDate:    Tue, 23 Feb 2021 12:03:19 +01:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Sat, 06 Mar 2021 12:08:53 +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@suse.de>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Link: https://lkml.kernel.org/r/20210223111130.16201-1-bp@alien8.de
---
 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);
 	}