FAILED: patch "[PATCH] KVM: x86: Register perf callbacks after calling vendor's" failed to apply to 4.19-stable tree

FAILED: patch "[PATCH] KVM: x86: Register perf callbacks after calling vendor's" failed to apply to 4.19-stable tree

[gregkh]

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 5c7df80e2ce4c954c80eb4ecf5fa002a5ff5d2d6 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Thu, 11 Nov 2021 02:07:23 +0000
Subject: [PATCH] KVM: x86: Register perf callbacks after calling vendor's
 hardware_setup()

Wait to register perf callbacks until after doing vendor hardaware setup.
VMX's hardware_setup() configures Intel Processor Trace (PT) mode, and a
future fix to register the Intel PT guest interrupt hook if and only if
Intel PT is exposed to the guest will consume the configured PT mode.

Delaying registration to hardware setup is effectively a nop as KVM's perf
hooks all pivot on the per-CPU current_vcpu, which is non-NULL only when
KVM is handling an IRQ/NMI in a VM-Exit path.  I.e. current_vcpu will be
NULL throughout both kvm_arch_init() and kvm_arch_hardware_setup().

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211111020738.2512932-3-seanjc@google.com

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dc7eb5fddfd3..50f0cd16f2d4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8626,8 +8626,6 @@ int kvm_arch_init(void *opaque)
 
 	kvm_timer_init();
 
-	perf_register_guest_info_callbacks(&kvm_guest_cbs);
-
 	if (boot_cpu_has(X86_FEATURE_XSAVE)) {
 		host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
 		supported_xcr0 = host_xcr0 & KVM_SUPPORTED_XCR0;
@@ -8659,7 +8657,6 @@ void kvm_arch_exit(void)
 		clear_hv_tscchange_cb();
 #endif
 	kvm_lapic_exit();
-	perf_unregister_guest_info_callbacks(&kvm_guest_cbs);
 
 	if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
 		cpufreq_unregister_notifier(&kvmclock_cpufreq_notifier_block,
@@ -11225,6 +11222,8 @@ int kvm_arch_hardware_setup(void *opaque)
 	memcpy(&kvm_x86_ops, ops->runtime_ops, sizeof(kvm_x86_ops));
 	kvm_ops_static_call_update();
 
+	perf_register_guest_info_callbacks(&kvm_guest_cbs);
+
 	if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
 		supported_xss = 0;
 
@@ -11252,6 +11251,8 @@ int kvm_arch_hardware_setup(void *opaque)
 
 void kvm_arch_hardware_unsetup(void)
 {
+	perf_unregister_guest_info_callbacks(&kvm_guest_cbs);
+
 	static_call(kvm_x86_hardware_unsetup)();
 }