[coreboot-gerrit] Change in coreboot[master]: cpu/x86/cache: CLFLUSH programs to memory before running

[Angel Pons (Code Review)]

Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/37196 )

Change subject: cpu/x86/cache: CLFLUSH programs to memory before running
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Patch Set 13:

(1 comment)

https://review.coreboot.org/c/coreboot/+/37196/12/src/cpu/x86/cache/cache.c 
File src/cpu/x86/cache/cache.c:

https://review.coreboot.org/c/coreboot/+/37196/12/src/cpu/x86/cache/cache.c@... 
PS12, Line 24: CONFIG(X86_CLFLUSH_CAR)
> I'm curious, does the compiler optimize it differently? […]

I'm not sure if the compiler can infer that cpuid_edx has no side-effect, so it may not be able to optimize out the code as-is.

In any case, I'd write this function as follows:

bool clflush_supported(void)
 {
    /* CLFLUSH while operating in CAR might not be supported by platforms */
    if (ENV_CACHE_AS_RAM && !CONFIG(X86_CLFLUSH_CAR))
    	return false;

return !!(cpuid_edx(1) >> CPUID_FEATURE_CLFLUSH_BIT);
 }