xen: make direct versions of irq_enable/disable/save/restore to common code
Now that x86-64 has directly accessible percpu variables, it can also
implement the direct versions of these operations, which operate on a
vcpu_info structure directly embedded in the percpu area.
In fact, the 64-bit versions are more or less identical, and so can be
shared. The only two differences are:
1. xen_restore_fl_direct takes its argument in eax on 32-bit, and rdi on 64-bit.
Unfortunately it isn't possible to directly refer to the 2nd lsb of rdi directly
(as you can with %ah), so the code isn't quite as dense.
2. check_events needs to variants to save different registers.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S
new file mode 100644
index 0000000..4c6f967
--- /dev/null
+++ b/arch/x86/xen/xen-asm.S
@@ -0,0 +1,140 @@
+/*
+ Asm versions of Xen pv-ops, suitable for either direct use or inlining.
+ The inline versions are the same as the direct-use versions, with the
+ pre- and post-amble chopped off.
+
+ This code is encoded for size rather than absolute efficiency,
+ with a view to being able to inline as much as possible.
+
+ We only bother with direct forms (ie, vcpu in percpu data) of
+ the operations here; the indirect forms are better handled in
+ C, since they're generally too large to inline anyway.
+ */
+
+#include <asm/asm-offsets.h>
+#include <asm/percpu.h>
+#include <asm/processor-flags.h>
+
+#include "xen-asm.h"
+
+/*
+ Enable events. This clears the event mask and tests the pending
+ event status with one and operation. If there are pending
+ events, then enter the hypervisor to get them handled.
+ */
+ENTRY(xen_irq_enable_direct)
+ /* Unmask events */
+ movb $0, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
+
+ /* Preempt here doesn't matter because that will deal with
+ any pending interrupts. The pending check may end up being
+ run on the wrong CPU, but that doesn't hurt. */
+
+ /* Test for pending */
+ testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
+ jz 1f
+
+2: call check_events
+1:
+ENDPATCH(xen_irq_enable_direct)
+ ret
+ ENDPROC(xen_irq_enable_direct)
+ RELOC(xen_irq_enable_direct, 2b+1)
+
+
+/*
+ Disabling events is simply a matter of making the event mask
+ non-zero.
+ */
+ENTRY(xen_irq_disable_direct)
+ movb $1, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
+ENDPATCH(xen_irq_disable_direct)
+ ret
+ ENDPROC(xen_irq_disable_direct)
+ RELOC(xen_irq_disable_direct, 0)
+
+/*
+ (xen_)save_fl is used to get the current interrupt enable status.
+ Callers expect the status to be in X86_EFLAGS_IF, and other bits
+ may be set in the return value. We take advantage of this by
+ making sure that X86_EFLAGS_IF has the right value (and other bits
+ in that byte are 0), but other bits in the return value are
+ undefined. We need to toggle the state of the bit, because
+ Xen and x86 use opposite senses (mask vs enable).
+ */
+ENTRY(xen_save_fl_direct)
+ testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
+ setz %ah
+ addb %ah,%ah
+ENDPATCH(xen_save_fl_direct)
+ ret
+ ENDPROC(xen_save_fl_direct)
+ RELOC(xen_save_fl_direct, 0)
+
+
+/*
+ In principle the caller should be passing us a value return
+ from xen_save_fl_direct, but for robustness sake we test only
+ the X86_EFLAGS_IF flag rather than the whole byte. After
+ setting the interrupt mask state, it checks for unmasked
+ pending events and enters the hypervisor to get them delivered
+ if so.
+ */
+ENTRY(xen_restore_fl_direct)
+#ifdef CONFIG_X86_64
+ testw $X86_EFLAGS_IF, %di
+#else
+ testb $X86_EFLAGS_IF>>8, %ah
+#endif
+ setz PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
+ /* Preempt here doesn't matter because that will deal with
+ any pending interrupts. The pending check may end up being
+ run on the wrong CPU, but that doesn't hurt. */
+
+ /* check for unmasked and pending */
+ cmpw $0x0001, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
+ jz 1f
+2: call check_events
+1:
+ENDPATCH(xen_restore_fl_direct)
+ ret
+ ENDPROC(xen_restore_fl_direct)
+ RELOC(xen_restore_fl_direct, 2b+1)
+
+
+/*
+ Force an event check by making a hypercall,
+ but preserve regs before making the call.
+ */
+check_events:
+#ifdef CONFIG_X86_32
+ push %eax
+ push %ecx
+ push %edx
+ call xen_force_evtchn_callback
+ pop %edx
+ pop %ecx
+ pop %eax
+#else
+ push %rax
+ push %rcx
+ push %rdx
+ push %rsi
+ push %rdi
+ push %r8
+ push %r9
+ push %r10
+ push %r11
+ call xen_force_evtchn_callback
+ pop %r11
+ pop %r10
+ pop %r9
+ pop %r8
+ pop %rdi
+ pop %rsi
+ pop %rdx
+ pop %rcx
+ pop %rax
+#endif
+ ret
+