path: root/virt
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authorMarc Zyngier <maz@kernel.org>2019-08-02 11:37:09 +0100
committerMarc Zyngier <maz@kernel.org>2019-08-18 18:50:44 +0100
commit07ab0f8d9a129add914aff3e988da4033471dfc0 (patch)
tree4cd843fb35c7ceae08922bad7a4e9a2ea640cca7 /virt
parent0ed5f5d63963673ccdd00d101637bf56e6d3d6dc (diff)
KVM: Call kvm_arch_vcpu_blocking early into the blocking sequence
When a vpcu is about to block by calling kvm_vcpu_block, we call back into the arch code to allow any form of synchronization that may be required at this point (SVN stops the AVIC, ARM synchronises the VMCR and enables GICv4 doorbells). But this synchronization comes in quite late, as we've potentially waited for halt_poll_ns to expire. Instead, let's move kvm_arch_vcpu_blocking() to the beginning of kvm_vcpu_block(), which on ARM has several benefits: - VMCR gets synchronised early, meaning that any interrupt delivered during the polling window will be evaluated with the correct guest PMR - GICv4 doorbells are enabled, which means that any guest interrupt directly injected during that window will be immediately recognised Tang Nianyao ran some tests on a GICv4 machine to evaluate such change, and reported up to a 10% improvement for netperf: <quote> netperf result: D06 as server, intel 8180 server as client with change: package 512 bytes - 5500 Mbits/s package 64 bytes - 760 Mbits/s without change: package 512 bytes - 5000 Mbits/s package 64 bytes - 710 Mbits/s </quote> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Marc Zyngier <maz@kernel.org>
Diffstat (limited to 'virt')
1 files changed, 3 insertions, 4 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index c6a91b044d8d..e6de3159e682 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2321,6 +2321,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
bool waited = false;
u64 block_ns;
+ kvm_arch_vcpu_blocking(vcpu);
start = cur = ktime_get();
if (vcpu->halt_poll_ns && !kvm_arch_no_poll(vcpu)) {
ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);
@@ -2341,8 +2343,6 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
} while (single_task_running() && ktime_before(cur, stop));
- kvm_arch_vcpu_blocking(vcpu);
for (;;) {
prepare_to_swait_exclusive(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
@@ -2355,9 +2355,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
finish_swait(&vcpu->wq, &wait);
cur = ktime_get();
- kvm_arch_vcpu_unblocking(vcpu);
+ kvm_arch_vcpu_unblocking(vcpu);
block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
if (!vcpu_valid_wakeup(vcpu))

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