7eb7ce4d2e
In xen_restore_fl_direct(), xen_force_evtchn_callback() was being called even if no events were pending. This resulted in (depending on workload) about a 100 times as many xen_version hypercalls as necessary. Fix this by correcting the sense of the conditional jump. This seems to give a significant performance benefit for some workloads. There is some subtle tricksy "..since the check here is trying to check both pending and masked in a single cmpw, but I think this is correct. It will call check_events now only when the combined mask+pending word is 0x0001 (aka unmasked, pending)." (Ian) CC: stable@kernel.org Acked-by: Ian Campbell <ian.campbell@citrix.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
142 lines
3.6 KiB
ArmAsm
142 lines
3.6 KiB
ArmAsm
/*
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* Asm versions of Xen pv-ops, suitable for either direct use or
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* inlining. The inline versions are the same as the direct-use
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* versions, with the pre- and post-amble chopped off.
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*
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* This code is encoded for size rather than absolute efficiency, with
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* a view to being able to inline as much as possible.
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*
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* We only bother with direct forms (ie, vcpu in percpu data) of the
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* operations here; the indirect forms are better handled in C, since
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* they're generally too large to inline anyway.
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*/
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#include <asm/asm-offsets.h>
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#include <asm/percpu.h>
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#include <asm/processor-flags.h>
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#include "xen-asm.h"
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/*
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* Enable events. This clears the event mask and tests the pending
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* event status with one and operation. If there are pending events,
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* then enter the hypervisor to get them handled.
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*/
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ENTRY(xen_irq_enable_direct)
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/* Unmask events */
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movb $0, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
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/*
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* Preempt here doesn't matter because that will deal with any
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* pending interrupts. The pending check may end up being run
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* on the wrong CPU, but that doesn't hurt.
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*/
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/* Test for pending */
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testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
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jz 1f
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2: call check_events
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1:
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ENDPATCH(xen_irq_enable_direct)
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ret
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ENDPROC(xen_irq_enable_direct)
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RELOC(xen_irq_enable_direct, 2b+1)
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/*
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* Disabling events is simply a matter of making the event mask
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* non-zero.
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*/
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ENTRY(xen_irq_disable_direct)
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movb $1, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
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ENDPATCH(xen_irq_disable_direct)
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ret
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ENDPROC(xen_irq_disable_direct)
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RELOC(xen_irq_disable_direct, 0)
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/*
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* (xen_)save_fl is used to get the current interrupt enable status.
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* Callers expect the status to be in X86_EFLAGS_IF, and other bits
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* may be set in the return value. We take advantage of this by
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* making sure that X86_EFLAGS_IF has the right value (and other bits
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* in that byte are 0), but other bits in the return value are
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* undefined. We need to toggle the state of the bit, because Xen and
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* x86 use opposite senses (mask vs enable).
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*/
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ENTRY(xen_save_fl_direct)
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testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
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setz %ah
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addb %ah, %ah
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ENDPATCH(xen_save_fl_direct)
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ret
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ENDPROC(xen_save_fl_direct)
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RELOC(xen_save_fl_direct, 0)
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/*
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* In principle the caller should be passing us a value return from
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* xen_save_fl_direct, but for robustness sake we test only the
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* X86_EFLAGS_IF flag rather than the whole byte. After setting the
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* interrupt mask state, it checks for unmasked pending events and
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* enters the hypervisor to get them delivered if so.
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*/
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ENTRY(xen_restore_fl_direct)
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#ifdef CONFIG_X86_64
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testw $X86_EFLAGS_IF, %di
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#else
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testb $X86_EFLAGS_IF>>8, %ah
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#endif
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setz PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
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/*
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* Preempt here doesn't matter because that will deal with any
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* pending interrupts. The pending check may end up being run
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* on the wrong CPU, but that doesn't hurt.
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*/
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/* check for unmasked and pending */
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cmpw $0x0001, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
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jnz 1f
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2: call check_events
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1:
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ENDPATCH(xen_restore_fl_direct)
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ret
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ENDPROC(xen_restore_fl_direct)
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RELOC(xen_restore_fl_direct, 2b+1)
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/*
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* Force an event check by making a hypercall, but preserve regs
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* before making the call.
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*/
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check_events:
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#ifdef CONFIG_X86_32
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push %eax
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push %ecx
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push %edx
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call xen_force_evtchn_callback
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pop %edx
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pop %ecx
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pop %eax
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#else
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push %rax
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push %rcx
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push %rdx
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push %rsi
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push %rdi
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push %r8
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push %r9
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push %r10
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push %r11
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call xen_force_evtchn_callback
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pop %r11
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pop %r10
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pop %r9
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pop %r8
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pop %rdi
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pop %rsi
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pop %rdx
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pop %rcx
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pop %rax
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#endif
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ret
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