perf/x86: always warn about broken BIOS
Subsystems (2)
PATCH 1/1 perf/x86: always warn about broken BIOS
The intialization function checks for various failure scenarios, but unfortunately the compiler gets a little confused about the possible combinations, leading to a false-positive build warning when -Wmaybe-uninitialized is set:
arch/x86/events/core.c: In function ‘init_hw_perf_events’:arch/x86/events/core.c:264:3: warning: ‘reg_fail’ may be used uninitialized in this function [-Wmaybe-uninitialized] arch/x86/events/core.c:264:3: warning: ‘val_fail’ may be used uninitialized in this function [-Wmaybe-uninitialized]
pr_err(FW_BUG "the BIOS has corrupted hw-PMU resources (MSR %x is %Lx)\n",
It seems reasonable to move the check for the broken BIOS a little higher in the function, which will lead to the kernel warning about both the BIOS and and broken hardware if both are faulty, but it has no effect otherwise at runtime.
Moving it ahead of the check for broken hardware however gets rid of the compile-time warning.
--- arch/x86/events/core.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)
arch/x86/events/core.c +9 -9
@@ -228,6 +228,15 @@ static bool check_hw_exists(void) }/* +* We still allow the PMU driver to operate: +*/ +if (bios_fail) { +pr_cont ("Broken BIOS detected, complain to your hardware vendor.\n" ); +pr_err (FW_BUG "the BIOS has corrupted hw-PMU resources (MSR %x is %Lx)\n" , + reg_fail, val_fail); + } + +/* * If all the counters are enabled, the below test will always * fail. The tools will also become useless in this scenario. * Just fail and disable the hardware counters.
@@ -252,15 +261,6 @@ static bool check_hw_exists(void)if (ret || val != val_new) goto msr_fail; -/* -* We still allow the PMU driver to operate: -*/ -if (bios_fail) { -pr_cont ("Broken BIOS detected, complain to your hardware vendor.\n" ); -pr_err (FW_BUG "the BIOS has corrupted hw-PMU resources (MSR %x is %Lx)\n" , - reg_fail, val_fail); - } -return true; msr_fail:
Signature · 1 line
2.9.0
Peter Zijlstra
maintainerQuoted 15 lines · Arnd Bergmann
The intialization function checks for various failure scenarios, but unfortunately the compiler gets a little confused about the possible combinations, leading to a false-positive build warning when -Wmaybe-uninitialized is set:
arch/x86/events/core.c: In function ‘init_hw_perf_events’:arch/x86/events/core.c:264:3: warning: ‘reg_fail’ may be used uninitialized in this function [-Wmaybe-uninitialized]arch/x86/events/core.c:264:3: warning: ‘val_fail’ may be used uninitialized in this function [-Wmaybe-uninitialized]
pr_err(FW_BUG "the BIOS has corrupted hw-PMU resources (MSR %x is %Lx)\n",It seems reasonable to move the check for the broken BIOS a little higher in the function, which will lead to the kernel warning about both the BIOS and and broken hardware if both are faulty, but it has no effect otherwise at runtime.
Quoted 4 lines
Moving it ahead of the check for broken hardware however gets rid of the compile-time warning.
Signed-off-by Arnd Bergmann <[email protected]>
Wouldn't something simple like this not be, well, simpler?
---
arch/x86/events/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
arch/x86/events/core.c +2 -2
@@ -190,8 +190,8 @@ static void release_pmc_hardware(void) {}static bool check_hw_exists (void ) { -u64 val, val_fail, val_new= ~0 ; -int i, reg, reg_fail, ret =0 ; +u64 val, val_fail =0 , val_new= ~0 ; +int i, reg, reg_fail =0 , ret =0 ;int bios_fail =0 ;int reg_safe =-1 ;