paravirt: clean up lazy mode handling

Currently, the set_lazy_mode pv_op is overloaded with 5 functions:
 1. enter lazy cpu mode
 2. leave lazy cpu mode
 3. enter lazy mmu mode
 4. leave lazy mmu mode
 5. flush pending batched operations

This complicates each paravirt backend, since it needs to deal with
all the possible state transitions, handling flushing, etc. In
particular, flushing is quite distinct from the other 4 functions, and
seems to just cause complication.

This patch removes the set_lazy_mode operation, and adds "enter" and
"leave" lazy mode operations on mmu_ops and cpu_ops.  All the logic
associated with enter and leaving lazy states is now in common code
(basically BUG_ONs to make sure that no mode is current when entering
a lazy mode, and make sure that the mode is current when leaving).
Also, flush is handled in a common way, by simply leaving and
re-entering the lazy mode.

The result is that the Xen, lguest and VMI lazy mode implementations
are much simpler.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Zach Amsden <zach@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Avi Kivity <avi@qumranet.com>
Cc: Anthony Liguory <aliguori@us.ibm.com>
Cc: "Glauber de Oliveira Costa" <glommer@gmail.com>
Cc: Jun Nakajima <jun.nakajima@intel.com>

2 files changed, 76 insertions, 21 deletions

diff --git a/arch/x86/kernel/paravirt_32.c b/arch/x86/kernel/paravirt_32.c
index fa412515af79..6a80d67c2121 100644
--- a/arch/x86/kernel/paravirt_32.c
+++ b/arch/x86/kernel/paravirt_32.c
@@ -164,7 +164,6 @@ static void *get_call_destination(u8 type)
 {
         struct paravirt_patch_template tmpl = {
                 .pv_init_ops = pv_init_ops,
-                .pv_misc_ops = pv_misc_ops,
                 .pv_time_ops = pv_time_ops,
                 .pv_cpu_ops = pv_cpu_ops,
                 .pv_irq_ops = pv_irq_ops,
@@ -282,6 +281,49 @@ int paravirt_disable_iospace(void)
         return ret;
 }
 
+static DEFINE_PER_CPU(enum paravirt_lazy_mode, paravirt_lazy_mode) = PARAVIRT_LAZY_NONE;
+
+static inline void enter_lazy(enum paravirt_lazy_mode mode)
+{
+        BUG_ON(x86_read_percpu(paravirt_lazy_mode) != PARAVIRT_LAZY_NONE);
+        BUG_ON(preemptible());
+
+        x86_write_percpu(paravirt_lazy_mode, mode);
+}
+
+void paravirt_leave_lazy(enum paravirt_lazy_mode mode)
+{
+        BUG_ON(x86_read_percpu(paravirt_lazy_mode) != mode);
+        BUG_ON(preemptible());
+
+        x86_write_percpu(paravirt_lazy_mode, PARAVIRT_LAZY_NONE);
+}
+
+void paravirt_enter_lazy_mmu(void)
+{
+        enter_lazy(PARAVIRT_LAZY_MMU);
+}
+
+void paravirt_leave_lazy_mmu(void)
+{
+        paravirt_leave_lazy(PARAVIRT_LAZY_MMU);
+}
+
+void paravirt_enter_lazy_cpu(void)
+{
+        enter_lazy(PARAVIRT_LAZY_CPU);
+}
+
+void paravirt_leave_lazy_cpu(void)
+{
+        paravirt_leave_lazy(PARAVIRT_LAZY_CPU);
+}
+
+enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
+{
+        return x86_read_percpu(paravirt_lazy_mode);
+}
+
 struct pv_info pv_info = {
         .name = "bare hardware",
         .paravirt_enabled = 0,
@@ -347,6 +389,11 @@ struct pv_cpu_ops pv_cpu_ops = {
 
         .set_iopl_mask = native_set_iopl_mask,
         .io_delay = native_io_delay,
+
+        .lazy_mode = {
+                .enter = paravirt_nop,
+                .leave = paravirt_nop,
+        },
 };
 
 struct pv_apic_ops pv_apic_ops = {
@@ -360,10 +407,6 @@ struct pv_apic_ops pv_apic_ops = {
 #endif
 };
 
-struct pv_misc_ops pv_misc_ops = {
-        .set_lazy_mode = paravirt_nop,
-};
-
 struct pv_mmu_ops pv_mmu_ops = {
         .pagetable_setup_start = native_pagetable_setup_start,
         .pagetable_setup_done = native_pagetable_setup_done,
@@ -414,6 +457,11 @@ struct pv_mmu_ops pv_mmu_ops = {
         .dup_mmap = paravirt_nop,
         .exit_mmap = paravirt_nop,
         .activate_mm = paravirt_nop,
+
+        .lazy_mode = {
+                .enter = paravirt_nop,
+                .leave = paravirt_nop,
+        },
 };
 
 EXPORT_SYMBOL_GPL(pv_time_ops);
diff --git a/arch/x86/kernel/vmi_32.c b/arch/x86/kernel/vmi_32.c
index 67cea5c2e3e0..f02bad68abaa 100644
--- a/arch/x86/kernel/vmi_32.c
+++ b/arch/x86/kernel/vmi_32.c
@@ -552,24 +552,22 @@ vmi_startup_ipi_hook(int phys_apicid, unsigned long start_eip,
 }
 #endif
 
-static void vmi_set_lazy_mode(enum paravirt_lazy_mode mode)
+static void vmi_enter_lazy_cpu(void)
 {
-        static DEFINE_PER_CPU(enum paravirt_lazy_mode, lazy_mode);
-
-        if (!vmi_ops.set_lazy_mode)
-                return;
+        paravirt_enter_lazy_cpu();
+        vmi_ops.set_lazy_mode(2);
+}
 
-        /* Modes should never nest or overlap */
-        BUG_ON(__get_cpu_var(lazy_mode) && !(mode == PARAVIRT_LAZY_NONE ||
-                                             mode == PARAVIRT_LAZY_FLUSH));
+static void vmi_enter_lazy_mmu(void)
+{
+        paravirt_enter_lazy_mmu();
+        vmi_ops.set_lazy_mode(1);
+}
 
-        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 void vmi_leave_lazy(void)
+{
+        paravirt_leave_lazy(paravirt_get_lazy_mode());
+        vmi_ops.set_lazy_mode(0);
 }
 
 static inline int __init check_vmi_rom(struct vrom_header *rom)
@@ -798,7 +796,16 @@ static inline int __init activate_vmi(void)
         para_wrap(pv_cpu_ops.load_esp0, vmi_load_esp0, set_kernel_stack, UpdateKernelStack);
         para_fill(pv_cpu_ops.set_iopl_mask, SetIOPLMask);
         para_fill(pv_cpu_ops.io_delay, IODelay);
-        para_wrap(pv_misc_ops.set_lazy_mode, vmi_set_lazy_mode, set_lazy_mode, SetLazyMode);
+
+        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,
+                  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,
+                  set_lazy_mode, SetLazyMode);
 
         /* user and kernel flush are just handled with different flags to FlushTLB */
         para_wrap(pv_mmu_ops.flush_tlb_user, vmi_flush_tlb_user, _flush_tlb, FlushTLB);