[PATCH] x86/sev: Disable ftrace branch profiling in SEV startup code

[PATCH] x86/sev: Disable ftrace branch profiling in SEV startup code

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb@kernel.org>

Ftrace branch profiling inserts absolute references to its metadata at
call sites, and this implies that this kind of instrumentation cannot be
used while executing from the 1:1 mapping of memory.

Therefore, disable ftrace branch profiling in the SEV startup routines,
by disabling it for the entire SEV core source file.

Cc: Tom Lendacky <thomas.lendacky@amd.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501072244.zZrx9864-lkp@intel.com/
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/coco/sev/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 86898547056e..b5c6c4afd1cc 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -9,6 +9,8 @@
 
 #define pr_fmt(fmt)	"SEV: " fmt
 
+#define DISABLE_BRANCH_PROFILING
+
 #include <linux/sched/debug.h>	/* For show_regs() */
 #include <linux/percpu-defs.h>
 #include <linux/cc_platform.h>
-- 
2.47.1.613.gc27f4b7a9f-goog

[tip: x86/boot] x86/sev: Disable ftrace branch profiling in SEV startup code

[tip-bot2 for Ard Biesheuvel]

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

Commit-ID:     cf4ca80650908628bf1c0c29e3fd236b1915d789
Gitweb:        https://git.kernel.org/tip/cf4ca80650908628bf1c0c29e3fd236b1915d789
Author:        Ard Biesheuvel <ardb@kernel.org>
AuthorDate:    Tue, 07 Jan 2025 16:18:27 +01:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Tue, 14 Jan 2025 19:10:32 +01:00

x86/sev: Disable ftrace branch profiling in SEV startup code

Ftrace branch profiling inserts absolute references to its metadata at
call sites, and this implies that this kind of instrumentation cannot be
used while executing from the 1:1 mapping of memory.

Therefore, disable ftrace branch profiling in the SEV startup routines,
by disabling it for the entire SEV core source file.

Closes: https://lore.kernel.org/oe-kbuild-all/202501072244.zZrx9864-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20250107151826.820147-2-ardb+git@google.com
---
 arch/x86/coco/sev/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 8689854..b5c6c4a 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -9,6 +9,8 @@
 
 #define pr_fmt(fmt)	"SEV: " fmt
 
+#define DISABLE_BRANCH_PROFILING
+
 #include <linux/sched/debug.h>	/* For show_regs() */
 #include <linux/percpu-defs.h>
 #include <linux/cc_platform.h>