Shenming,
Somehow this patch ended up in the wrong folder.
Apologies for the delay reviewing it.
On 2020-09-23 07:35, Shenming Lu wrote:
Right after a vPE is made resident, the code starts polling the
GICR_VPENDBASER.Dirty bit until it becomes 0, where the delay_us
is set to 10. But in our measurement, it takes only hundreds of
nanoseconds, or 1~2 microseconds, to finish parsing the VPT in most
cases. And we also measured the time from vcpu_load() (include it)
to __guest_enter() on Kunpeng 920. On average, it takes 2.55
microseconds
(not first run && the VPT is empty). So 10 microseconds delay might
really hurt performance.
To avoid this, we can set the delay_us to 1, which is more appropriate
in this situation and universal. Besides, we can delay the execution
of its_wait_vpt_parse_complete() (call it from kvm_vgic_flush_hwstate()
corresponding to vPE resident), giving the GIC a chance to work in
parallel with the CPU on the entry path.
Signed-off-by: Shenming Lu <lushenming@xxxxxxxxxx>
---
arch/arm64/kvm/vgic/vgic-v4.c | 18 ++++++++++++++++++
arch/arm64/kvm/vgic/vgic.c | 2 ++
drivers/irqchip/irq-gic-v3-its.c | 14 +++++++++++---
drivers/irqchip/irq-gic-v4.c | 11 +++++++++++
include/kvm/arm_vgic.h | 3 +++
include/linux/irqchip/arm-gic-v4.h | 4 ++++
6 files changed, 49 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kvm/vgic/vgic-v4.c
b/arch/arm64/kvm/vgic/vgic-v4.c
index b5fa73c9fd35..1d5d2d6894d3 100644
--- a/arch/arm64/kvm/vgic/vgic-v4.c
+++ b/arch/arm64/kvm/vgic/vgic-v4.c
@@ -353,6 +353,24 @@ int vgic_v4_load(struct kvm_vcpu *vcpu)
return err;
}
+void vgic_v4_wait_vpt(struct kvm_vcpu *vcpu)
I'd like something a bit more abstract as a name.
vgic_v4_commit() seems more appropriate, and could be used for other
purposes.
+{
+ struct its_vpe *vpe;
+
+ if (kvm_vgic_global_state.type == VGIC_V2 ||
Why do you test for GICv2? Isn't the vgic_supports_direct_msis() test
enough?
And the test should be moved to kvm_vgic_flush_hwstate(), as we already
have
similar checks there.
!vgic_supports_direct_msis(vcpu->kvm))
+ return;
+
+ vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
+
+ if (vpe->vpt_ready)
+ return;
+
+ if (its_wait_vpt(vpe))
+ return;
How can that happen?
+
+ vpe->vpt_ready = true;
This is nasty. You need to explain what happens with this state (you are
trying not to access VPENDBASER across a shallow exit, as only a
vcpu_put
will invalidate the GIC state). And something like vpe_ready is more
generic (we try not to have too much of the GICv4 gunk in the KVM code).
+}
+
static struct vgic_its *vgic_get_its(struct kvm *kvm,
struct kvm_kernel_irq_routing_entry *irq_entry)
{
diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index c3643b7f101b..ed810a80cda2 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -915,6 +915,8 @@ void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu)
if (can_access_vgic_from_kernel())
vgic_restore_state(vcpu);
+
+ vgic_v4_wait_vpt(vcpu);
}
void kvm_vgic_load(struct kvm_vcpu *vcpu)
diff --git a/drivers/irqchip/irq-gic-v3-its.c
b/drivers/irqchip/irq-gic-v3-its.c
index 548de7538632..b7cbc9bcab9d 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -3803,7 +3803,7 @@ static void its_wait_vpt_parse_complete(void)
WARN_ON_ONCE(readq_relaxed_poll_timeout_atomic(vlpi_base +
GICR_VPENDBASER,
val,
!(val & GICR_VPENDBASER_Dirty),
- 10, 500));
+ 1, 500));
This really should be in a separate patch.
}
static void its_vpe_schedule(struct its_vpe *vpe)
@@ -3837,7 +3837,7 @@ static void its_vpe_schedule(struct its_vpe *vpe)
val |= GICR_VPENDBASER_Valid;
gicr_write_vpendbaser(val, vlpi_base + GICR_VPENDBASER);
- its_wait_vpt_parse_complete();
+ vpe->vpt_ready = false;
This really belongs to the deschedule path, doesn't it? Given that
it can only be set from vgic_flush_hwstate(), it should be fairly
foolproof.
}
static void its_vpe_deschedule(struct its_vpe *vpe)
@@ -3881,6 +3881,10 @@ static int its_vpe_set_vcpu_affinity(struct
irq_data *d, void *vcpu_info)
its_vpe_schedule(vpe);
return 0;
+ case WAIT_VPT:
COMMIT_VPE seems a better name.
+ its_wait_vpt_parse_complete();
+ return 0;
+
case DESCHEDULE_VPE:
its_vpe_deschedule(vpe);
return 0;
@@ -4047,7 +4051,7 @@ static void its_vpe_4_1_schedule(struct its_vpe
*vpe,
gicr_write_vpendbaser(val, vlpi_base + GICR_VPENDBASER);
- its_wait_vpt_parse_complete();
+ vpe->vpt_ready = false;
}
static void its_vpe_4_1_deschedule(struct its_vpe *vpe,
@@ -4118,6 +4122,10 @@ static int its_vpe_4_1_set_vcpu_affinity(struct
irq_data *d, void *vcpu_info)
its_vpe_4_1_schedule(vpe, info);
return 0;
+ case WAIT_VPT:
+ its_wait_vpt_parse_complete();
+ return 0;
+
case DESCHEDULE_VPE:
its_vpe_4_1_deschedule(vpe, info);
return 0;
diff --git a/drivers/irqchip/irq-gic-v4.c
b/drivers/irqchip/irq-gic-v4.c
index 0c18714ae13e..36be42569872 100644
--- a/drivers/irqchip/irq-gic-v4.c
+++ b/drivers/irqchip/irq-gic-v4.c
@@ -258,6 +258,17 @@ int its_make_vpe_resident(struct its_vpe *vpe,
bool g0en, bool g1en)
return ret;
}
+int its_wait_vpt(struct its_vpe *vpe)
its_commit_vpe()
+{
+ struct its_cmd_info info = { };
+
+ WARN_ON(preemptible());
+
+ info.cmd_type = WAIT_VPT;
Please write it as:
struct its_cmd_info = {
.cmd_type = COMMIT_VPE,
};
as for most of the commands.
+
+ return its_send_vpe_cmd(vpe, &info);
+}
+
int its_invall_vpe(struct its_vpe *vpe)
{
struct its_cmd_info info = {
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index a8d8fdcd3723..b55a835d28a8 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -402,6 +402,9 @@ int kvm_vgic_v4_unset_forwarding(struct kvm *kvm,
int irq,
struct kvm_kernel_irq_routing_entry *irq_entry);
int vgic_v4_load(struct kvm_vcpu *vcpu);
+
+void vgic_v4_wait_vpt(struct kvm_vcpu *vcpu);
+
int vgic_v4_put(struct kvm_vcpu *vcpu, bool need_db);
#endif /* __KVM_ARM_VGIC_H */
diff --git a/include/linux/irqchip/arm-gic-v4.h
b/include/linux/irqchip/arm-gic-v4.h
index 6976b8331b60..68ac2b7b9309 100644
--- a/include/linux/irqchip/arm-gic-v4.h
+++ b/include/linux/irqchip/arm-gic-v4.h
@@ -75,6 +75,8 @@ struct its_vpe {
u16 vpe_id;
/* Pending VLPIs on schedule out? */
bool pending_last;
+ /* VPT parse complete */
+ bool vpt_ready;
};
/*
@@ -103,6 +105,7 @@ enum its_vcpu_info_cmd_type {
PROP_UPDATE_VLPI,
PROP_UPDATE_AND_INV_VLPI,
SCHEDULE_VPE,
+ WAIT_VPT,
DESCHEDULE_VPE,
INVALL_VPE,
PROP_UPDATE_VSGI,
@@ -128,6 +131,7 @@ struct its_cmd_info {
int its_alloc_vcpu_irqs(struct its_vm *vm);
void its_free_vcpu_irqs(struct its_vm *vm);
int its_make_vpe_resident(struct its_vpe *vpe, bool g0en, bool g1en);
+int its_wait_vpt(struct its_vpe *vpe);
int its_make_vpe_non_resident(struct its_vpe *vpe, bool db);
int its_invall_vpe(struct its_vpe *vpe);
int its_map_vlpi(int irq, struct its_vlpi_map *map);
My comments are mostly cosmetic. If you can respin quickly, I'll
pick it up for 5.11.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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