Messages in this thread Patch in this message | | | From | Bryan O'Donoghue <> | Subject | [PATCH 2/2] x86: Quark: Comment setup_arch for TLB/PGE bugfix | Date | Wed, 1 Oct 2014 00:41:57 +0100 |
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Quark X1000 requires CR3 to be rewritten to flush TLB entries irrespective of the PGE bits in CR4 or PTE.PGE
Add a comment to setup_arch to indicate that the code
load_cr3(swapper_pg_dir); __flush_tlb_all();
Will already have flushed the TLB @ the CR3 reload allowing us to skip over a potential if/else for Quark.
This comment clearly states the bug, the behaviour we rely on and the reason why we only do it this way - one time.
Later on cpu_has_pge() will be false due to a fixup in intel_init_early() and __flush_tlb_all() will work as expected from that point onwards
Signed-off-by: Bryan O'Donoghue <pure.logic@nexus-software.ie> --- arch/x86/kernel/setup.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 41ead8d..235cfd3 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -879,6 +879,15 @@ void __init setup_arch(char **cmdline_p) KERNEL_PGD_PTRS); load_cr3(swapper_pg_dir); + /* + * Note: Quark X1000 CPUs advertise PGE incorrectly and require + * a cr3 based tlb flush, so the following __flush_tlb_all() + * will not flush anything because the cpu quirk which clears + * X86_FEATURE_PGE has not been invoked yet. Though due to the + * load_cr3() above the TLB has been flushed already. The + * quirk is invoked before subsequent calls to __flush_tlb_all() + * so proper operation is guaranteed. + */ __flush_tlb_all(); #else printk(KERN_INFO "Command line: %s\n", boot_command_line); -- 1.9.1
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