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    Subject[PATCH 5/9] x86/paravirt: flush pending mmu updates on context switch
    Date
    From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

    If we're in lazy mmu mode when context switching, leave
    lazy mmu mode, but remember the task's state in
    TIF_LAZY_MMU_UPDATES. When we resume the task, check this
    flag and re-enter lazy mmu mode if its set.

    This sets things up for allowing lazy mmu mode while preemptible,
    though that won't actually be active until the next change.

    Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    ---
    arch/x86/include/asm/paravirt.h | 1 -
    arch/x86/include/asm/thread_info.h | 2 ++
    arch/x86/kernel/kvm.c | 2 +-
    arch/x86/kernel/paravirt.c | 13 ++++++++++---
    arch/x86/kernel/vmi_32.c | 14 ++++++++++----
    arch/x86/lguest/boot.c | 14 ++++++++++----
    arch/x86/xen/enlighten.c | 6 +++---
    arch/x86/xen/mmu.c | 7 ++++++-
    arch/x86/xen/xen-ops.h | 1 -
    9 files changed, 42 insertions(+), 18 deletions(-)

    diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
    index 7b28aba..58d2481 100644
    --- a/arch/x86/include/asm/paravirt.h
    +++ b/arch/x86/include/asm/paravirt.h
    @@ -1418,7 +1418,6 @@ void paravirt_enter_lazy_cpu(void);
    void paravirt_leave_lazy_cpu(void);
    void paravirt_enter_lazy_mmu(void);
    void paravirt_leave_lazy_mmu(void);
    -void paravirt_leave_lazy(enum paravirt_lazy_mode mode);

    #define __HAVE_ARCH_START_CONTEXT_SWITCH
    static inline void arch_start_context_switch(void)
    diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
    index ca7310e..b857399 100644
    --- a/arch/x86/include/asm/thread_info.h
    +++ b/arch/x86/include/asm/thread_info.h
    @@ -95,6 +95,7 @@ struct thread_info {
    #define TIF_FORCED_TF 24 /* true if TF in eflags artificially */
    #define TIF_DEBUGCTLMSR 25 /* uses thread_struct.debugctlmsr */
    #define TIF_DS_AREA_MSR 26 /* uses thread_struct.ds_area_msr */
    +#define TIF_LAZY_MMU_UPDATES 27 /* task is updating the mmu lazily */

    #define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
    #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
    @@ -117,6 +118,7 @@ struct thread_info {
    #define _TIF_FORCED_TF (1 << TIF_FORCED_TF)
    #define _TIF_DEBUGCTLMSR (1 << TIF_DEBUGCTLMSR)
    #define _TIF_DS_AREA_MSR (1 << TIF_DS_AREA_MSR)
    +#define _TIF_LAZY_MMU_UPDATES (1 << TIF_LAZY_MMU_UPDATES)

    /* work to do in syscall_trace_enter() */
    #define _TIF_WORK_SYSCALL_ENTRY \
    diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
    index 478bca9..5d7f6e7 100644
    --- a/arch/x86/kernel/kvm.c
    +++ b/arch/x86/kernel/kvm.c
    @@ -201,7 +201,7 @@ static void kvm_leave_lazy_mmu(void)
    struct kvm_para_state *state = kvm_para_state();

    mmu_queue_flush(state);
    - paravirt_leave_lazy(paravirt_get_lazy_mode());
    + paravirt_leave_lazy_mmu();
    state->mode = paravirt_get_lazy_mode();
    }

    diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
    index ef3ca17..554dadd 100644
    --- a/arch/x86/kernel/paravirt.c
    +++ b/arch/x86/kernel/paravirt.c
    @@ -253,7 +253,7 @@ static inline void enter_lazy(enum paravirt_lazy_mode mode)
    __get_cpu_var(paravirt_lazy_mode) = mode;
    }

    -void paravirt_leave_lazy(enum paravirt_lazy_mode mode)
    +static void leave_lazy(enum paravirt_lazy_mode mode)
    {
    BUG_ON(__get_cpu_var(paravirt_lazy_mode) != mode);
    BUG_ON(preemptible());
    @@ -268,17 +268,24 @@ void paravirt_enter_lazy_mmu(void)

    void paravirt_leave_lazy_mmu(void)
    {
    - paravirt_leave_lazy(PARAVIRT_LAZY_MMU);
    + leave_lazy(PARAVIRT_LAZY_MMU);
    }

    void paravirt_enter_lazy_cpu(void)
    {
    + if (percpu_read(paravirt_lazy_mode) == PARAVIRT_LAZY_MMU) {
    + arch_leave_lazy_mmu_mode();
    + set_thread_flag(TIF_LAZY_MMU_UPDATES);
    + }
    enter_lazy(PARAVIRT_LAZY_CPU);
    }

    void paravirt_leave_lazy_cpu(void)
    {
    - paravirt_leave_lazy(PARAVIRT_LAZY_CPU);
    + leave_lazy(PARAVIRT_LAZY_CPU);
    +
    + if (test_and_clear_thread_flag(TIF_LAZY_MMU_UPDATES))
    + arch_enter_lazy_mmu_mode();
    }

    enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
    diff --git a/arch/x86/kernel/vmi_32.c b/arch/x86/kernel/vmi_32.c
    index 2cc4a90..950929c 100644
    --- a/arch/x86/kernel/vmi_32.c
    +++ b/arch/x86/kernel/vmi_32.c
    @@ -473,16 +473,22 @@ static void vmi_enter_lazy_cpu(void)
    vmi_ops.set_lazy_mode(2);
    }

    +static void vmi_leave_lazy_cpu(void)
    +{
    + vmi_ops.set_lazy_mode(0);
    + paravirt_leave_lazy_cpu();
    +}
    +
    static void vmi_enter_lazy_mmu(void)
    {
    paravirt_enter_lazy_mmu();
    vmi_ops.set_lazy_mode(1);
    }

    -static void vmi_leave_lazy(void)
    +static void vmi_leave_lazy_mmu(void)
    {
    - paravirt_leave_lazy(paravirt_get_lazy_mode());
    vmi_ops.set_lazy_mode(0);
    + paravirt_leave_lazy_mmu();
    }

    static inline int __init check_vmi_rom(struct vrom_header *rom)
    @@ -718,12 +724,12 @@ static inline int __init activate_vmi(void)

    para_wrap(pv_cpu_ops.lazy_mode.enter, vmi_enter_lazy_cpu,
    set_lazy_mode, SetLazyMode);
    - para_wrap(pv_cpu_ops.lazy_mode.leave, vmi_leave_lazy,
    + para_wrap(pv_cpu_ops.lazy_mode.leave, vmi_leave_lazy_cpu,
    set_lazy_mode, SetLazyMode);

    para_wrap(pv_mmu_ops.lazy_mode.enter, vmi_enter_lazy_mmu,
    set_lazy_mode, SetLazyMode);
    - para_wrap(pv_mmu_ops.lazy_mode.leave, vmi_leave_lazy,
    + para_wrap(pv_mmu_ops.lazy_mode.leave, vmi_leave_lazy_mmu,
    set_lazy_mode, SetLazyMode);

    /* user and kernel flush are just handled with different flags to FlushTLB */
    diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
    index f3a5305..804c170 100644
    --- a/arch/x86/lguest/boot.c
    +++ b/arch/x86/lguest/boot.c
    @@ -147,10 +147,16 @@ static void lazy_hcall(unsigned long call,

    /* When lazy mode is turned off reset the per-cpu lazy mode variable and then
    * issue the do-nothing hypercall to flush any stored calls. */
    -static void lguest_leave_lazy_mode(void)
    +static void lguest_leave_lazy_mmu_mode(void)
    {
    - paravirt_leave_lazy(paravirt_get_lazy_mode());
    hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0);
    + paravirt_leave_lazy_mmu();
    +}
    +
    +static void lguest_leave_lazy_cpu_mode(void)
    +{
    + hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0);
    + paravirt_leave_lazy_cpu();
    }

    /*G:033
    @@ -1019,7 +1025,7 @@ __init void lguest_init(void)
    pv_cpu_ops.write_idt_entry = lguest_write_idt_entry;
    pv_cpu_ops.wbinvd = lguest_wbinvd;
    pv_cpu_ops.lazy_mode.enter = paravirt_enter_lazy_cpu;
    - pv_cpu_ops.lazy_mode.leave = lguest_leave_lazy_mode;
    + pv_cpu_ops.lazy_mode.leave = lguest_leave_lazy_cpu_mode;

    /* pagetable management */
    pv_mmu_ops.write_cr3 = lguest_write_cr3;
    @@ -1032,7 +1038,7 @@ __init void lguest_init(void)
    pv_mmu_ops.read_cr2 = lguest_read_cr2;
    pv_mmu_ops.read_cr3 = lguest_read_cr3;
    pv_mmu_ops.lazy_mode.enter = paravirt_enter_lazy_mmu;
    - pv_mmu_ops.lazy_mode.leave = lguest_leave_lazy_mode;
    + pv_mmu_ops.lazy_mode.leave = lguest_leave_lazy_mmu_mode;

    #ifdef CONFIG_X86_LOCAL_APIC
    /* apic read/write intercepts */
    diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
    index 86497d5..fc6519a 100644
    --- a/arch/x86/xen/enlighten.c
    +++ b/arch/x86/xen/enlighten.c
    @@ -203,10 +203,10 @@ static unsigned long xen_get_debugreg(int reg)
    return HYPERVISOR_get_debugreg(reg);
    }

    -void xen_leave_lazy(void)
    +static void xen_leave_lazy_cpu(void)
    {
    - paravirt_leave_lazy(paravirt_get_lazy_mode());
    xen_mc_flush();
    + paravirt_leave_lazy_cpu();
    }

    static unsigned long xen_store_tr(void)
    @@ -817,7 +817,7 @@ static const struct pv_cpu_ops xen_cpu_ops __initdata = {

    .lazy_mode = {
    .enter = paravirt_enter_lazy_cpu,
    - .leave = xen_leave_lazy,
    + .leave = xen_leave_lazy_cpu,
    },
    };

    diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
    index 298b9f5..2669c58 100644
    --- a/arch/x86/xen/mmu.c
    +++ b/arch/x86/xen/mmu.c
    @@ -1809,6 +1809,11 @@ __init void xen_post_allocator_init(void)
    xen_mark_init_mm_pinned();
    }

    +static void xen_leave_lazy_mmu(void)
    +{
    + xen_mc_flush();
    + paravirt_leave_lazy_mmu();
    +}

    const struct pv_mmu_ops xen_mmu_ops __initdata = {
    .pagetable_setup_start = xen_pagetable_setup_start,
    @@ -1884,7 +1889,7 @@ const struct pv_mmu_ops xen_mmu_ops __initdata = {

    .lazy_mode = {
    .enter = paravirt_enter_lazy_mmu,
    - .leave = xen_leave_lazy,
    + .leave = xen_leave_lazy_mmu,
    },

    .set_fixmap = xen_set_fixmap,
    diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
    index 2f5ef26..f897cdf 100644
    --- a/arch/x86/xen/xen-ops.h
    +++ b/arch/x86/xen/xen-ops.h
    @@ -30,7 +30,6 @@ pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
    void xen_ident_map_ISA(void);
    void xen_reserve_top(void);

    -void xen_leave_lazy(void);
    void xen_post_allocator_init(void);

    char * __init xen_memory_setup(void);
    --
    1.6.0.6


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