From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Nitesh Narayan Lal <nitesh@redhat.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Maxim Levitsky <mlevitsk@redhat.com>,
Eduardo Habkost <ehabkost@redhat.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH v5 2/8] KVM: KVM: Use cpumask_available() to check for NULL cpumask when kicking vCPUs
Date: Fri, 3 Sep 2021 09:51:35 +0200 [thread overview]
Message-ID: <20210903075141.403071-3-vkuznets@redhat.com> (raw)
In-Reply-To: <20210903075141.403071-1-vkuznets@redhat.com>
From: Sean Christopherson <seanjc@google.com>
Check for a NULL cpumask_var_t when kicking multiple vCPUs via
cpumask_available(), which performs a !NULL check if and only if cpumasks
are configured to be allocated off-stack. This is a meaningless
optimization, e.g. avoids a TEST+Jcc and TEST+CMOV on x86, but more
importantly helps document that the NULL check is necessary even though
all callers pass in a local variable.
No functional change intended.
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
virt/kvm/kvm_main.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 786b914db98f..2082aceffbf6 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -245,9 +245,13 @@ static void ack_flush(void *_completed)
{
}
-static inline bool kvm_kick_many_cpus(const struct cpumask *cpus, bool wait)
+static inline bool kvm_kick_many_cpus(cpumask_var_t tmp, bool wait)
{
- if (unlikely(!cpus))
+ const struct cpumask *cpus;
+
+ if (likely(cpumask_available(tmp)))
+ cpus = tmp;
+ else
cpus = cpu_online_mask;
if (cpumask_empty(cpus))
@@ -277,6 +281,14 @@ bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
if (!(req & KVM_REQUEST_NO_WAKEUP) && kvm_vcpu_wake_up(vcpu))
continue;
+ /*
+ * tmp can be "unavailable" if cpumasks are allocated off stack
+ * as allocation of the mask is deliberately not fatal and is
+ * handled by falling back to kicking all online CPUs.
+ */
+ if (!cpumask_available(tmp))
+ continue;
+
/*
* Note, the vCPU could get migrated to a different pCPU at any
* point after kvm_request_needs_ipi(), which could result in
@@ -288,7 +300,7 @@ bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
* were reading SPTEs _before_ any changes were finalized. See
* kvm_vcpu_kick() for more details on handling requests.
*/
- if (tmp != NULL && kvm_request_needs_ipi(vcpu, req)) {
+ if (kvm_request_needs_ipi(vcpu, req)) {
cpu = READ_ONCE(vcpu->cpu);
if (cpu != -1 && cpu != me)
__cpumask_set_cpu(cpu, tmp);
--
2.31.1
next prev parent reply other threads:[~2021-09-03 7:52 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-03 7:51 [PATCH v5 0/8] KVM: Various fixes and improvements around kicking vCPUs Vitaly Kuznetsov
2021-09-03 7:51 ` [PATCH v5 1/8] KVM: Clean up benign vcpu->cpu data races when " Vitaly Kuznetsov
2021-09-04 0:52 ` Lai Jiangshan
2021-09-03 7:51 ` Vitaly Kuznetsov [this message]
2021-09-03 7:51 ` [PATCH v5 3/8] KVM: x86: hyper-v: Avoid calling kvm_make_vcpus_request_mask() with vcpu_mask==NULL Vitaly Kuznetsov
2021-09-03 7:51 ` [PATCH v5 4/8] KVM: Optimize kvm_make_vcpus_request_mask() a bit Vitaly Kuznetsov
2021-09-03 16:22 ` Sean Christopherson
2021-09-03 7:51 ` [PATCH v5 5/8] KVM: Drop 'except' parameter from kvm_make_vcpus_request_mask() Vitaly Kuznetsov
2021-09-03 7:51 ` [PATCH v5 6/8] KVM: x86: Fix stack-out-of-bounds memory access from ioapic_write_indirect() Vitaly Kuznetsov
2021-09-03 7:51 ` [PATCH v5 7/8] KVM: Pre-allocate cpumasks for kvm_make_all_cpus_request_except() Vitaly Kuznetsov
2021-09-03 16:24 ` Sean Christopherson
2021-09-03 7:51 ` [PATCH v5 8/8] KVM: Make kvm_make_vcpus_request_mask() use pre-allocated cpu_kick_mask Vitaly Kuznetsov
2021-09-03 16:26 ` Sean Christopherson
2021-09-06 7:23 ` Vitaly Kuznetsov
2021-09-20 14:48 ` [PATCH v5 0/8] KVM: Various fixes and improvements around kicking vCPUs Vitaly Kuznetsov
2021-09-20 18:04 ` Paolo Bonzini
2021-09-24 11:05 ` Paolo Bonzini
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