Commit 0bbc2ca8 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: KVM: Use cpumask_available() to check for NULL cpumask when kicking vCPUs 



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: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210827092516.1027264-3-vkuznets@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 85b64045

virt/kvm/kvm_main.c

+15 −3
Original line number Diff line number Diff line
@@ -235,9 +235,13 @@ 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))
@@ -267,6 +271,14 @@ 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
@@ -278,7 +290,7 @@ 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);