KVM: Remove kvm_make_all_cpus_request_except()

Remove kvm_make_all_cpus_request_except() as it effectively has no users,
and arguably should never have been added in the first place.

Commit 54163a3 ("KVM: Introduce kvm_make_all_cpus_request_except()")
added the "except" variation for use in SVM's AVIC update path, which used
it to skip sending a request to the current vCPU (commit 7d61123
("KVM: SVM: Disable AVIC before setting V_IRQ")).

But the AVIC usage of kvm_make_all_cpus_request_except() was essentially a
hack-a-fix that simply squashed the most likely scenario of a racy WARN
without addressing the underlying problem(s).  Commit f1577ab ("KVM:
SVM: svm_set_vintr don't warn if AVIC is active but is about to be
deactivated") eventually fixed the WARN itself, and the "except" usage was
subsequently dropped by df63202 ("KVM: x86: APICv: drop immediate
APICv disablement on current vCPU").

That kvm_make_all_cpus_request_except() hasn't gained any users in the
last ~3 years isn't a coincidence.  If a VM-wide broadcast *needs* to skip
the current vCPU, then odds are very good that there is underlying bug
that could be better fixed elsewhere.

Signed-off-by: Venkatesh Srinivas <venkateshs@chromium.org>
Link: https://lore.kernel.org/r/20240404232651.1645176-1-venkateshs@chromium.org
[sean: rewrite changelog with --verbose]
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: vsrinivas

include/linux/kvm_host.h

@@ -193,8 +193,6 @@ static inline bool is_error_page(struct page *page)
 bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
 				 unsigned long *vcpu_bitmap);
 bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req);
-bool kvm_make_all_cpus_request_except(struct kvm *kvm, unsigned int req,
-				      struct kvm_vcpu *except);
 
 #define KVM_USERSPACE_IRQ_SOURCE_ID		0
 #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID	1

virt/kvm/kvm_main.c

@@ -311,8 +311,7 @@ bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
 	return called;
 }
 
-bool kvm_make_all_cpus_request_except(struct kvm *kvm, unsigned int req,
-				      struct kvm_vcpu *except)
+bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
 {
 	struct kvm_vcpu *vcpu;
 	struct cpumask *cpus;
@@ -325,22 +324,14 @@ bool kvm_make_all_cpus_request_except(struct kvm *kvm, unsigned int req,
 	cpus = this_cpu_cpumask_var_ptr(cpu_kick_mask);
 	cpumask_clear(cpus);
 
-	kvm_for_each_vcpu(i, vcpu, kvm) {
-		if (vcpu == except)
-			continue;
+	kvm_for_each_vcpu(i, vcpu, kvm)
 		kvm_make_vcpu_request(vcpu, req, cpus, me);
-	}
 
 	called = kvm_kick_many_cpus(cpus, !!(req & KVM_REQUEST_WAIT));
 	put_cpu();
 
 	return called;
 }
-
-bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
-{
-	return kvm_make_all_cpus_request_except(kvm, req, NULL);
-}
 EXPORT_SYMBOL_GPL(kvm_make_all_cpus_request);
 
 void kvm_flush_remote_tlbs(struct kvm *kvm)