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Date: Tue, 6 Jun 2017 12:57:07 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: Longpeng <longpeng2@...wei.com>,
Huangweidong <weidong.huang@...wei.com>,
Gonglei <arei.gonglei@...wei.com>,
wangxin <wangxinxin.wang@...wei.com>,
Radim Krčmář <rkrcmar@...hat.com>
Subject: [PATCH 4/4] KVM: VMX: simplify cmpxchg of PI descriptor control field
Introduce new helpers __pi_set_ndst and pi_try_cmpxchg_control.
Cc: Longpeng (Mike) <longpeng2@...wei.com>
Cc: Huangweidong <weidong.huang@...wei.com>
Cc: Gonglei <arei.gonglei@...wei.com>
Cc: wangxin <wangxinxin.wang@...wei.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
arch/x86/kvm/vmx.c | 83 ++++++++++++++++++++++++++----------------------------
1 file changed, 40 insertions(+), 43 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 81047f373747..4f6b5fa57bbc 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -560,6 +560,29 @@ static inline int pi_test_sn(struct pi_desc *pi_desc)
(unsigned long *)&pi_desc->control);
}
+/* Note that this is not an atomic operation. */
+static inline void __pi_set_ndst(struct pi_desc *pi_desc, unsigned cpu)
+{
+ unsigned dest = cpu_physical_id(cpu);
+
+ if (x2apic_enabled())
+ pi_desc->ndst = dest;
+ else
+ pi_desc->ndst = (dest << 8) & 0xFF00;
+}
+
+static inline bool pi_try_cmpxchg_control(struct pi_desc *pi_desc,
+ struct pi_desc *old,
+ struct pi_desc *new)
+{
+ if (cmpxchg(&pi_desc->control, old->control,
+ new->control) == old->control)
+ return true;
+
+ old->control = READ_ONCE(pi_desc->control);
+ return false;
+}
+
struct vcpu_vmx {
struct kvm_vcpu vcpu;
unsigned long host_rsp;
@@ -2182,7 +2205,6 @@ static void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
{
struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
struct pi_desc old, new;
- unsigned int dest;
/*
* In case of hot-plug or hot-unplug, we may have to undo
@@ -2209,19 +2231,12 @@ static void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
}
/* The full case. */
+ old.control = pi_desc->control;
do {
- old.control = new.control = pi_desc->control;
-
- dest = cpu_physical_id(cpu);
-
- if (x2apic_enabled())
- new.ndst = dest;
- else
- new.ndst = (dest << 8) & 0xFF00;
-
+ new.control = old.control;
+ __pi_set_ndst(&new, cpu);
new.sn = 0;
- } while (cmpxchg(&pi_desc->control, old.control,
- new.control) != old.control);
+ } while (!pi_try_cmpxchg_control(pi_desc, &old, &new));
}
static void decache_tsc_multiplier(struct vcpu_vmx *vmx)
@@ -11240,24 +11255,16 @@ static void __pi_post_block(struct kvm_vcpu *vcpu)
{
struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
struct pi_desc old, new;
- unsigned int dest;
+ old.control = pi_desc->control;
do {
- old.control = new.control = pi_desc->control;
WARN(old.nv != POSTED_INTR_WAKEUP_VECTOR,
"Wakeup handler not enabled while the VCPU is blocked\n");
- dest = cpu_physical_id(vcpu->cpu);
-
- if (x2apic_enabled())
- new.ndst = dest;
- else
- new.ndst = (dest << 8) & 0xFF00;
-
- /* set 'NV' to 'notification vector' */
+ new.control = old.control;
+ __pi_set_ndst(&new, vcpu->cpu);
new.nv = POSTED_INTR_VECTOR;
- } while (cmpxchg(&pi_desc->control, old.control,
- new.control) != old.control);
+ } while (!pi_try_cmpxchg_control(pi_desc, &old, &new));
if (!WARN_ON_ONCE(vcpu->pre_pcpu == -1)) {
spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));
@@ -11265,6 +11272,7 @@ static void __pi_post_block(struct kvm_vcpu *vcpu)
spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));
vcpu->pre_pcpu = -1;
}
+
}
/*
@@ -11282,7 +11290,6 @@ static void __pi_post_block(struct kvm_vcpu *vcpu)
*/
static int pi_pre_block(struct kvm_vcpu *vcpu)
{
- unsigned int dest;
struct pi_desc old, new;
struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
@@ -11302,32 +11309,22 @@ static int pi_pre_block(struct kvm_vcpu *vcpu)
spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));
}
+ old.control = pi_desc->control;
do {
- old.control = new.control = pi_desc->control;
-
WARN((pi_desc->sn == 1),
"Warning: SN field of posted-interrupts "
"is set before blocking\n");
/*
- * Since vCPU can be preempted during this process,
- * vcpu->cpu could be different with pre_pcpu, we
- * need to set pre_pcpu as the destination of wakeup
- * notification event, then we can find the right vCPU
- * to wakeup in wakeup handler if interrupts happen
- * when the vCPU is in blocked state.
+ * The wakeup_handler expects the VCPU to be on the
+ * blocked_vcpu_list that matches ndst. Interrupts
+ * are disabled so no preemption should happen, but
+ * err on the side of safety.
*/
- dest = cpu_physical_id(vcpu->pre_pcpu);
-
- if (x2apic_enabled())
- new.ndst = dest;
- else
- new.ndst = (dest << 8) & 0xFF00;
-
- /* set 'NV' to 'wakeup vector' */
+ new.control = old.control;
+ __pi_set_ndst(&new, vcpu->pre_pcpu);
new.nv = POSTED_INTR_WAKEUP_VECTOR;
- } while (cmpxchg(&pi_desc->control, old.control,
- new.control) != old.control);
+ } while (!pi_try_cmpxchg_control(pi_desc, &old, &new));
/* We should not block the vCPU if an interrupt is posted for it. */
if (pi_test_on(pi_desc) == 1)
--
2.13.0
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