From 49f19710512c825aaea73b9207b3a848027cda1d Mon Sep 17 00:00:00 2001 From: Zachary Amsden Date: Sun, 8 Apr 2007 16:04:01 -0700 Subject: [PATCH] Proper fix for highmem kmap_atomic functions for VMI for 2.6.21 Since lazy MMU batching mode still allows interrupts to enter, it is possible for interrupt handlers to try to use kmap_atomic, which fails when lazy mode is active, since the PTE update to highmem will be delayed. The best workaround is to issue an explicit flush in kmap_atomic_functions case; this is the only way nested PTE updates can happen in the interrupt handler. Thanks to Jeremy Fitzhardinge for noting the bug and suggestions on a fix. This patch gets reverted again when we start 2.6.22 and the bug gets fixed differently. Signed-off-by: Zachary Amsden Cc: Andi Kleen Cc: Jeremy Fitzhardinge Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/vmi.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) (limited to 'arch/i386/kernel') diff --git a/arch/i386/kernel/vmi.c b/arch/i386/kernel/vmi.c index fb07a1aad22..edc339fa503 100644 --- a/arch/i386/kernel/vmi.c +++ b/arch/i386/kernel/vmi.c @@ -69,6 +69,7 @@ struct { void (*flush_tlb)(int); void (*set_initial_ap_state)(int, int); void (*halt)(void); + void (*set_lazy_mode)(int mode); } vmi_ops; /* XXX move this to alternative.h */ @@ -574,6 +575,26 @@ vmi_startup_ipi_hook(int phys_apicid, unsigned long start_eip, } #endif +static void vmi_set_lazy_mode(int mode) +{ + static DEFINE_PER_CPU(int, lazy_mode); + + if (!vmi_ops.set_lazy_mode) + return; + + /* Modes should never nest or overlap */ + BUG_ON(__get_cpu_var(lazy_mode) && !(mode == PARAVIRT_LAZY_NONE || + mode == PARAVIRT_LAZY_FLUSH)); + + if (mode == PARAVIRT_LAZY_FLUSH) { + vmi_ops.set_lazy_mode(0); + vmi_ops.set_lazy_mode(__get_cpu_var(lazy_mode)); + } else { + vmi_ops.set_lazy_mode(mode); + __get_cpu_var(lazy_mode) = mode; + } +} + static inline int __init check_vmi_rom(struct vrom_header *rom) { struct pci_header *pci; @@ -804,7 +825,7 @@ static inline int __init activate_vmi(void) para_wrap(load_esp0, vmi_load_esp0, set_kernel_stack, UpdateKernelStack); para_fill(set_iopl_mask, SetIOPLMask); para_fill(io_delay, IODelay); - para_fill(set_lazy_mode, SetLazyMode); + para_wrap(set_lazy_mode, vmi_set_lazy_mode, set_lazy_mode, SetLazyMode); /* user and kernel flush are just handled with different flags to FlushTLB */ para_wrap(flush_tlb_user, vmi_flush_tlb_user, flush_tlb, FlushTLB); -- cgit v1.2.3