Messages in this thread | | | Date | Thu, 25 Sep 2014 10:35:51 +0100 | From | Bryan O'Donoghue <> | Subject | Re: [PATCH] x86: Quark: Flush TLB via CR3 not CR4.PGE in setup_arch() |
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>> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c >> index 41ead8d..1d2396a 100644 >> --- a/arch/x86/kernel/setup.c >> +++ b/arch/x86/kernel/setup.c >> @@ -879,7 +879,10 @@ void __init setup_arch(char **cmdline_p) >> KERNEL_PGD_PTRS); >> >> load_cr3(swapper_pg_dir); >> - __flush_tlb_all(); >> + if (boot_cpu_data.x86 == 5 && boot_cpu_data.x86_model == 9) >> + __flush_tlb(); >> + else >> + __flush_tlb_all(); > > So why not make __flush_tlb_all() Quark-quirk-aware and be done > with it, instead of having to validate every single > __flush_tlb_all() user? > > Quark breaks the x86 'flush all TLBs' semantics - the way to fix > it is to restore those semantics, not to sprinkle the breakage > all around the code ...
Hi Ingo.
We have made __flush_tlb_all() Quark aware - because the previous patch we applied to arch/x86/kernel/cpu/intel.c
ee1b5b165c0a2f04d2107e634e51f05d0eb107de
+ if (c->x86 == 5 && c->x86_model == 9) { + pr_info("Disabling PGE capability bit\n"); + setup_clear_cpu_cap(X86_FEATURE_PGE); + }
will cause cpu_has_pge() to be false and then the flush_tlb_all code will take the path we want __flush_tlb not __flush_tlb_global
static inline void __flush_tlb_all(void) { if (cpu_has_pge) __flush_tlb_global(); else __flush_tlb(); }
The code in setup_arch runs before the cpu_has_pge bit been clobbered.
The commit you did 02276a3a677d681f0cd227d7111c71fdbce23832 just adds a comment to setup_arch to indicate the behaviour we are relying on
setup_arch() {
load_cr3(swapper_pg_dir); /* this will flush the TLB on Quark */ __flush_tlb_all(); /*cpu_has_pge() is true at this point*/
......
/* this is where we latch the cpu cabability bits */ early_cpu_init(); }
-- BOD
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