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[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 <zach@vmware.com> Cc: Andi Kleen <ak@muc.de> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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a5bfffac64
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4 changed files with 29 additions and 1 deletions
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@ -69,6 +69,7 @@ struct {
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void (*flush_tlb)(int);
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void (*set_initial_ap_state)(int, int);
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void (*halt)(void);
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void (*set_lazy_mode)(int mode);
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} vmi_ops;
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/* XXX move this to alternative.h */
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@ -574,6 +575,26 @@ vmi_startup_ipi_hook(int phys_apicid, unsigned long start_eip,
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}
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#endif
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static void vmi_set_lazy_mode(int mode)
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{
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static DEFINE_PER_CPU(int, lazy_mode);
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if (!vmi_ops.set_lazy_mode)
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return;
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/* Modes should never nest or overlap */
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BUG_ON(__get_cpu_var(lazy_mode) && !(mode == PARAVIRT_LAZY_NONE ||
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mode == PARAVIRT_LAZY_FLUSH));
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if (mode == PARAVIRT_LAZY_FLUSH) {
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vmi_ops.set_lazy_mode(0);
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vmi_ops.set_lazy_mode(__get_cpu_var(lazy_mode));
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} else {
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vmi_ops.set_lazy_mode(mode);
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__get_cpu_var(lazy_mode) = mode;
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}
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}
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static inline int __init check_vmi_rom(struct vrom_header *rom)
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{
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struct pci_header *pci;
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@ -804,7 +825,7 @@ static inline int __init activate_vmi(void)
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para_wrap(load_esp0, vmi_load_esp0, set_kernel_stack, UpdateKernelStack);
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para_fill(set_iopl_mask, SetIOPLMask);
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para_fill(io_delay, IODelay);
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para_fill(set_lazy_mode, SetLazyMode);
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para_wrap(set_lazy_mode, vmi_set_lazy_mode, set_lazy_mode, SetLazyMode);
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/* user and kernel flush are just handled with different flags to FlushTLB */
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para_wrap(flush_tlb_user, vmi_flush_tlb_user, flush_tlb, FlushTLB);
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@ -42,6 +42,7 @@ void *kmap_atomic(struct page *page, enum km_type type)
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vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
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set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
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arch_flush_lazy_mmu_mode();
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return (void*) vaddr;
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}
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@ -82,6 +83,7 @@ void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
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idx = type + KM_TYPE_NR*smp_processor_id();
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vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
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set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
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arch_flush_lazy_mmu_mode();
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return (void*) vaddr;
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}
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@ -180,6 +180,7 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
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#ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
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#define arch_enter_lazy_mmu_mode() do {} while (0)
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#define arch_leave_lazy_mmu_mode() do {} while (0)
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#define arch_flush_lazy_mmu_mode() do {} while (0)
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#endif
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/*
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@ -193,6 +194,7 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
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#ifndef __HAVE_ARCH_ENTER_LAZY_CPU_MODE
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#define arch_enter_lazy_cpu_mode() do {} while (0)
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#define arch_leave_lazy_cpu_mode() do {} while (0)
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#define arch_flush_lazy_cpu_mode() do {} while (0)
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#endif
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/*
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@ -421,14 +421,17 @@ static inline void pmd_clear(pmd_t *pmdp)
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#define PARAVIRT_LAZY_NONE 0
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#define PARAVIRT_LAZY_MMU 1
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#define PARAVIRT_LAZY_CPU 2
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#define PARAVIRT_LAZY_FLUSH 3
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#define __HAVE_ARCH_ENTER_LAZY_CPU_MODE
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#define arch_enter_lazy_cpu_mode() paravirt_ops.set_lazy_mode(PARAVIRT_LAZY_CPU)
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#define arch_leave_lazy_cpu_mode() paravirt_ops.set_lazy_mode(PARAVIRT_LAZY_NONE)
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#define arch_flush_lazy_cpu_mode() paravirt_ops.set_lazy_mode(PARAVIRT_LAZY_FLUSH)
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#define __HAVE_ARCH_ENTER_LAZY_MMU_MODE
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#define arch_enter_lazy_mmu_mode() paravirt_ops.set_lazy_mode(PARAVIRT_LAZY_MMU)
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#define arch_leave_lazy_mmu_mode() paravirt_ops.set_lazy_mode(PARAVIRT_LAZY_NONE)
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#define arch_flush_lazy_mmu_mode() paravirt_ops.set_lazy_mode(PARAVIRT_LAZY_FLUSH)
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/* These all sit in the .parainstructions section to tell us what to patch. */
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struct paravirt_patch {
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