Author: neel
Date: Fri Sep 12 06:15:20 2014
New Revision: 271451
URL: http://svnweb.freebsd.org/changeset/base/271451
Log:
Optimize the common case of injecting an interrupt into a vcpu after a HLT
by explicitly moving it out of the interrupt shadow. The hypervisor is done
"executing" the HLT and by definition this moves the vcpu out of the
1-instruction interrupt shadow.
Prior to this change the interrupt would be held pending because the VMCS
guest-interruptibility-state would indicate that "blocking by STI" was in
effect. This resulted in an unnecessary round trip into the guest before
the pending interrupt could be injected.
Reviewed by: grehan
Modified:
head/sys/amd64/include/vmm.h
head/sys/amd64/vmm/intel/vmx.c
head/sys/amd64/vmm/vmm.c
Modified: head/sys/amd64/include/vmm.h
==============================================================================
--- head/sys/amd64/include/vmm.h Fri Sep 12 05:25:56 2014
(r271450)
+++ head/sys/amd64/include/vmm.h Fri Sep 12 06:15:20 2014
(r271451)
@@ -82,6 +82,7 @@ enum vm_reg_name {
VM_REG_GUEST_PDPTE1,
VM_REG_GUEST_PDPTE2,
VM_REG_GUEST_PDPTE3,
+ VM_REG_GUEST_INTR_SHADOW,
VM_REG_LAST
};
Modified: head/sys/amd64/vmm/intel/vmx.c
==============================================================================
--- head/sys/amd64/vmm/intel/vmx.c Fri Sep 12 05:25:56 2014
(r271450)
+++ head/sys/amd64/vmm/intel/vmx.c Fri Sep 12 06:15:20 2014
(r271451)
@@ -2712,6 +2712,46 @@ vmxctx_setreg(struct vmxctx *vmxctx, int
}
static int
+vmx_get_intr_shadow(struct vmx *vmx, int vcpu, int running, uint64_t *retval)
+{
+ uint64_t gi;
+ int error;
+
+ error = vmcs_getreg(&vmx->vmcs[vcpu], running,
+ VMCS_IDENT(VMCS_GUEST_INTERRUPTIBILITY), &gi);
+ *retval = (gi & HWINTR_BLOCKING) ? 1 : 0;
+ return (error);
+}
+
+static int
+vmx_modify_intr_shadow(struct vmx *vmx, int vcpu, int running, uint64_t val)
+{
+ struct vmcs *vmcs;
+ uint64_t gi;
+ int error, ident;
+
+ /*
+ * Forcing the vcpu into an interrupt shadow is not supported.
+ */
+ if (val) {
+ error = EINVAL;
+ goto done;
+ }
+
+ vmcs = &vmx->vmcs[vcpu];
+ ident = VMCS_IDENT(VMCS_GUEST_INTERRUPTIBILITY);
+ error = vmcs_getreg(vmcs, running, ident, &gi);
+ if (error == 0) {
+ gi &= ~HWINTR_BLOCKING;
+ error = vmcs_setreg(vmcs, running, ident, gi);
+ }
+done:
+ VCPU_CTR2(vmx->vm, vcpu, "Setting intr_shadow to %#lx %s", val,
+ error ? "failed" : "succeeded");
+ return (error);
+}
+
+static int
vmx_shadow_reg(int reg)
{
int shreg;
@@ -2742,6 +2782,9 @@ vmx_getreg(void *arg, int vcpu, int reg,
if (running && hostcpu != curcpu)
panic("vmx_getreg: %s%d is running", vm_name(vmx->vm), vcpu);
+ if (reg == VM_REG_GUEST_INTR_SHADOW)
+ return (vmx_get_intr_shadow(vmx, vcpu, running, retval));
+
if (vmxctx_getreg(&vmx->ctx[vcpu], reg, retval) == 0)
return (0);
@@ -2760,6 +2803,9 @@ vmx_setreg(void *arg, int vcpu, int reg,
if (running && hostcpu != curcpu)
panic("vmx_setreg: %s%d is running", vm_name(vmx->vm), vcpu);
+ if (reg == VM_REG_GUEST_INTR_SHADOW)
+ return (vmx_modify_intr_shadow(vmx, vcpu, running, val));
+
if (vmxctx_setreg(&vmx->ctx[vcpu], reg, val) == 0)
return (0);
Modified: head/sys/amd64/vmm/vmm.c
==============================================================================
--- head/sys/amd64/vmm/vmm.c Fri Sep 12 05:25:56 2014 (r271450)
+++ head/sys/amd64/vmm/vmm.c Fri Sep 12 06:15:20 2014 (r271451)
@@ -1090,7 +1090,7 @@ vm_handle_hlt(struct vm *vm, int vcpuid,
{
struct vcpu *vcpu;
const char *wmesg;
- int t, vcpu_halted, vm_halted;
+ int error, t, vcpu_halted, vm_halted;
KASSERT(!CPU_ISSET(vcpuid, &vm->halted_cpus), ("vcpu already halted"));
@@ -1098,6 +1098,22 @@ vm_handle_hlt(struct vm *vm, int vcpuid,
vcpu_halted = 0;
vm_halted = 0;
+ /*
+ * The typical way to halt a cpu is to execute: "sti; hlt"
+ *
+ * STI sets RFLAGS.IF to enable interrupts. However, the processor
+ * remains in an "interrupt shadow" for an additional instruction
+ * following the STI. This guarantees that "sti; hlt" sequence is
+ * atomic and a pending interrupt will be recognized after the HLT.
+ *
+ * After the HLT emulation is done the vcpu is no longer in an
+ * interrupt shadow and a pending interrupt can be injected on
+ * the next entry into the guest.
+ */
+ error = vm_set_register(vm, vcpuid, VM_REG_GUEST_INTR_SHADOW, 0);
+ KASSERT(error == 0, ("%s: error %d clearing interrupt shadow",
+ __func__, error));
+
vcpu_lock(vcpu);
while (1) {
/*
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