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2075244f9b
Quark SoC X1000 advertises Page Global Enable for it's Translation Lookaside Buffer via cpuid. The silicon does not in fact support PGE and hence will not flush the TLB when CR4.PGE is rewritten. The Quark documentation makes clear the necessity to instead rewrite CR3 in order to flush any TLB entries, irrespective of the state of CR4.PGE or an individual PTE.PGE See Intel Quark Core DevMan_001.pdf section 6.4.11 In setup.c setup_arch() the code will load_cr3() and then do a __flush_tlb_all(). On Quark the entire TLB will be flushed at the load_cr3(). The __flush_tlb_all() have no effect and can be safely ignored. Later on in the boot process we switch off the flag for cpu_has_pge() which means that subsequent calls to __flush_tlb_all() will call __flush_tlb() not __flush_tlb_global() flushing the TLB in the correct way via load_cr3() not CR4.PGE rewrite This patch documents the behaviour of flushing the TLB for Quark in setup_arch() Comment text suggested by Thomas Gleixner Signed-off-by: Bryan O'Donoghue <pure.logic@nexus-software.ie> Cc: davej@redhat.com Cc: hmh@hmh.eng.br Link: http://lkml.kernel.org/r/1412641189-12415-2-git-send-email-pure.logic@nexus-software.ie Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
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