From: Sean Christopherson <seanjc@xxxxxxxxxx>
[ Upstream commit 0bbc2ca8515f9cdf11df84ccb63dc7c44bc3d8f4 ]
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@xxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Message-Id: <20210827092516.1027264-3-vkuznets@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Stable-dep-of: 2b0128127373 ("KVM: Register /dev/kvm as the _very_ last thing during initialization")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 b5134f3046483..f379398b43d59 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -248,9 +248,13 @@ 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))
@@ -280,6 +284,14 @@ 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
@@ -291,7 +303,7 @@ 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);
--
2.39.2
