FAILED: patch "[PATCH] KVM: x86/pmu: Do not mask LVTPC when handling a PMI on AMD" failed to apply to 4.19-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxx>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x 49ff3b4aec51e3abfc9369997cc603319b02af9a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2024042325-rockstar-civic-9c1a@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

49ff3b4aec51 ("KVM: x86/pmu: Do not mask LVTPC when handling a PMI on AMD platforms")
a16eb25b09c0 ("KVM: x86: Mask LVTPC when handling a PMI")

thanks,

greg k-h

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

>From 49ff3b4aec51e3abfc9369997cc603319b02af9a Mon Sep 17 00:00:00 2001
From: Sandipan Das <sandipan.das@xxxxxxx>
Date: Fri, 5 Apr 2024 16:55:55 -0700
Subject: [PATCH] KVM: x86/pmu: Do not mask LVTPC when handling a PMI on AMD
 platforms

On AMD and Hygon platforms, the local APIC does not automatically set
the mask bit of the LVTPC register when handling a PMI and there is
no need to clear it in the kernel's PMI handler.

For guests, the mask bit is currently set by kvm_apic_local_deliver()
and unless it is cleared by the guest kernel's PMI handler, PMIs stop
arriving and break use-cases like sampling with perf record.

This does not affect non-PerfMonV2 guests because PMIs are handled in
the guest kernel by x86_pmu_handle_irq() which always clears the LVTPC
mask bit irrespective of the vendor.

Before:

  $ perf record -e cycles:u true
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.001 MB perf.data (1 samples) ]

After:

  $ perf record -e cycles:u true
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.002 MB perf.data (19 samples) ]

Fixes: a16eb25b09c0 ("KVM: x86: Mask LVTPC when handling a PMI")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sandipan Das <sandipan.das@xxxxxxx>
Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
[sean: use is_intel_compatible instead of !is_amd_or_hygon()]
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-ID: <20240405235603.1173076-3-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index cf37586f0466..ebf41023be38 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2776,7 +2776,8 @@ int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type)
 		trig_mode = reg & APIC_LVT_LEVEL_TRIGGER;
 
 		r = __apic_accept_irq(apic, mode, vector, 1, trig_mode, NULL);
-		if (r && lvt_type == APIC_LVTPC)
+		if (r && lvt_type == APIC_LVTPC &&
+		    guest_cpuid_is_intel_compatible(apic->vcpu))
 			kvm_lapic_set_reg(apic, APIC_LVTPC, reg | APIC_LVT_MASKED);
 		return r;
 	}