xen: Attempt to patch inline versions of common operations

This patchs adds the mechanism to allow us to patch inline versions of
common operations.

The implementations of the direct-access versions save_fl, restore_fl,
irq_enable and irq_disable are now in assembler, and the same code is
used for both out of line and inline uses.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Keir Fraser <keir@xensource.com>

1 files changed, 54 insertions, 53 deletions

diff --git a/arch/i386/xen/enlighten.c b/arch/i386/xen/enlighten.c
index e33fa0990eda..4fa62a4cb7cc 100644
--- a/arch/i386/xen/enlighten.c
+++ b/arch/i386/xen/enlighten.c
@@ -115,6 +115,7 @@ static void __init xen_vcpu_setup(int cpu)
                 /* This cpu is using the registered vcpu info, even if
                    later ones fail to. */
                 per_cpu(xen_vcpu, cpu) = vcpup;
+
                 printk(KERN_DEBUG "cpu %d using vcpu_info at %p\n",
                        cpu, vcpup);
         }
@@ -177,20 +178,6 @@ static unsigned long xen_save_fl(void)
         return (-flags) & X86_EFLAGS_IF;
 }
 
-static unsigned long xen_save_fl_direct(void)
-{
-        unsigned long flags;
-
-        /* flag has opposite sense of mask */
-        flags = !x86_read_percpu(xen_vcpu_info.evtchn_upcall_mask);
-
-        /* convert to IF type flag
-           -0 -> 0x00000000
-           -1 -> 0xffffffff
-        */
-        return (-flags) & X86_EFLAGS_IF;
-}
-
 static void xen_restore_fl(unsigned long flags)
 {
         struct vcpu_info *vcpu;
@@ -217,25 +204,6 @@ static void xen_restore_fl(unsigned long flags)
         }
 }
 
-static void xen_restore_fl_direct(unsigned long flags)
-{
-        /* convert from IF type flag */
-        flags = !(flags & X86_EFLAGS_IF);
-
-        /* This is an atomic update, so no need to worry about
-           preemption. */
-        x86_write_percpu(xen_vcpu_info.evtchn_upcall_mask, flags);
-
-        /* If we get preempted here, then any pending event will be
-           handled anyway. */
-
-        if (flags == 0) {
-                barrier(); /* unmask then check (avoid races) */
-                if (unlikely(x86_read_percpu(xen_vcpu_info.evtchn_upcall_pending)))
-                        force_evtchn_callback();
-        }
-}
-
 static void xen_irq_disable(void)
 {
         /* There's a one instruction preempt window here.  We need to
@@ -246,12 +214,6 @@ static void xen_irq_disable(void)
         preempt_enable_no_resched();
 }
 
-static void xen_irq_disable_direct(void)
-{
-        /* Atomic update, so preemption not a concern. */
-        x86_write_percpu(xen_vcpu_info.evtchn_upcall_mask, 1);
-}
-
 static void xen_irq_enable(void)
 {
         struct vcpu_info *vcpu;
@@ -272,19 +234,6 @@ static void xen_irq_enable(void)
                 force_evtchn_callback();
 }
 
-static void xen_irq_enable_direct(void)
-{
-        /* Atomic update, so preemption not a concern. */
-        x86_write_percpu(xen_vcpu_info.evtchn_upcall_mask, 0);
-
-        /* Doesn't matter if we get preempted here, because any
-           pending event will get dealt with anyway. */
-
-        barrier(); /* unmask then check (avoid races) */
-        if (unlikely(x86_read_percpu(xen_vcpu_info.evtchn_upcall_pending)))
-                force_evtchn_callback();
-}
-
 static void xen_safe_halt(void)
 {
         /* Blocking includes an implicit local_irq_enable(). */
@@ -892,6 +841,57 @@ void __init xen_setup_vcpu_info_placement(void)
         }
 }
 
+static unsigned xen_patch(u8 type, u16 clobbers, void *insns, unsigned len)
+{
+        char *start, *end, *reloc;
+        unsigned ret;
+
+        start = end = reloc = NULL;
+
+#define SITE(x)                                                         \
+        case PARAVIRT_PATCH(x):                                         \
+        if (have_vcpu_info_placement) {                                 \
+                start = (char *)xen_##x##_direct;                       \
+                end = xen_##x##_direct_end;                             \
+                reloc = xen_##x##_direct_reloc;                         \
+        }                                                               \
+        goto patch_site
+
+        switch (type) {
+                SITE(irq_enable);
+                SITE(irq_disable);
+                SITE(save_fl);
+                SITE(restore_fl);
+#undef SITE
+
+        patch_site:
+                if (start == NULL || (end-start) > len)
+                        goto default_patch;
+
+                ret = paravirt_patch_insns(insns, len, start, end);
+
+                /* Note: because reloc is assigned from something that
+                   appears to be an array, gcc assumes it's non-null,
+                   but doesn't know its relationship with start and
+                   end. */
+                if (reloc > start && reloc < end) {
+                        int reloc_off = reloc - start;
+                        long *relocp = (long *)(insns + reloc_off);
+                        long delta = start - (char *)insns;
+
+                        *relocp += delta;
+                }
+                break;
+
+        default_patch:
+        default:
+                ret = paravirt_patch_default(type, clobbers, insns, len);
+                break;
+        }
+
+        return ret;
+}
+
 static const struct paravirt_ops xen_paravirt_ops __initdata = {
         .paravirt_enabled = 1,
         .shared_kernel_pmd = 0,
@@ -899,7 +899,7 @@ static const struct paravirt_ops xen_paravirt_ops __initdata = {
         .name = "Xen",
         .banner = xen_banner,
 
-        .patch = paravirt_patch_default,
+        .patch = xen_patch,
 
         .memory_setup = xen_memory_setup,
         .arch_setup = xen_arch_setup,
@@ -1076,6 +1076,7 @@ static const struct machine_ops __initdata xen_machine_ops = {
         .emergency_restart = xen_emergency_restart,
 };
 
+
 /* First C function to be called on Xen boot */
 asmlinkage void __init xen_start_kernel(void)
 {