linux-kernel - [PATCH] KVM: x86/pmu: Isolate TSX specific perf_event

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Date:   Mon,  7 Mar 2022 14:38:05 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Ravi Bangoria <ravi.bangoria@....com>,
        Jim Mattson <jmattson@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>, kvm@...r.kernel.org,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: x86/pmu: Isolate TSX specific perf_event_attr.attr logic for AMD

From: Like Xu <likexu@...cent.com>

HSW_IN_TX* bits are used in generic code which are not supported on
AMD. Worse, these bits overlap with AMD EventSelect[11:8] and hence
using HSW_IN_TX* bits unconditionally in generic code is resulting in
unintentional pmu behavior on AMD. For example, if EventSelect[11:8]
is 0x2, pmc_reprogram_counter() wrongly assumes that
HSW_IN_TX_CHECKPOINTED is set and thus forces sampling period to be 0.

Opportunistically remove two TSX specific incoming parameters for
the generic interface reprogram_counter().

Fixes: 103af0a98788 ("perf, kvm: Support the in_tx/in_tx_cp modifiers in KVM arch perfmon emulation v5")
Co-developed-by: Ravi Bangoria <ravi.bangoria@....com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
Signed-off-by: Like Xu <likexu@...cent.com>
---
Note: this patch is based on [1] which is considered to be a necessary cornerstone.
[1] https://lore.kernel.org/kvm/20220302111334.12689-1-likexu@tencent.com/

 arch/x86/kvm/pmu.c | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 17c61c990282..d0f9515c37dd 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -99,8 +99,7 @@ static void kvm_perf_overflow(struct perf_event *perf_event,
 
 static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
 				  u64 config, bool exclude_user,
-				  bool exclude_kernel, bool intr,
-				  bool in_tx, bool in_tx_cp)
+				  bool exclude_kernel, bool intr)
 {
 	struct perf_event *event;
 	struct perf_event_attr attr = {
@@ -116,16 +115,18 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
 
 	attr.sample_period = get_sample_period(pmc, pmc->counter);
 
-	if (in_tx)
-		attr.config |= HSW_IN_TX;
-	if (in_tx_cp) {
-		/*
-		 * HSW_IN_TX_CHECKPOINTED is not supported with nonzero
-		 * period. Just clear the sample period so at least
-		 * allocating the counter doesn't fail.
-		 */
-		attr.sample_period = 0;
-		attr.config |= HSW_IN_TX_CHECKPOINTED;
+	if (guest_cpuid_is_intel(pmc->vcpu)) {
+		if (pmc->eventsel & HSW_IN_TX)
+			attr.config |= HSW_IN_TX;
+		if (pmc->eventsel & HSW_IN_TX_CHECKPOINTED) {
+			/*
+			 * HSW_IN_TX_CHECKPOINTED is not supported with nonzero
+			 * period. Just clear the sample period so at least
+			 * allocating the counter doesn't fail.
+			 */
+			attr.sample_period = 0;
+			attr.config |= HSW_IN_TX_CHECKPOINTED;
+		}
 	}
 
 	event = perf_event_create_kernel_counter(&attr, -1, current,
@@ -268,9 +269,7 @@ void reprogram_counter(struct kvm_pmc *pmc)
 			(eventsel & AMD64_RAW_EVENT_MASK),
 			!(eventsel & ARCH_PERFMON_EVENTSEL_USR),
 			!(eventsel & ARCH_PERFMON_EVENTSEL_OS),
-			eventsel & ARCH_PERFMON_EVENTSEL_INT,
-			(eventsel & HSW_IN_TX),
-			(eventsel & HSW_IN_TX_CHECKPOINTED));
+			eventsel & ARCH_PERFMON_EVENTSEL_INT);
 }
 EXPORT_SYMBOL_GPL(reprogram_counter);
 
-- 
2.35.1