linux-kernel - Re: [RESEND PATCH] perf/x86/intel: Fix unchecked MSR access error for Alder Lake N

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Date:   Mon, 22 Aug 2022 16:39:32 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     acme@...hat.com, linux-kernel@...r.kernel.org,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com,
        Jianfeng Gao <jianfeng.gao@...el.com>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>
Subject: Re: [RESEND PATCH] perf/x86/intel: Fix unchecked MSR access error
 for Alder Lake N

On Mon, Aug 22, 2022 at 09:28:31AM -0400, Liang, Kan wrote:
> 
> 
> On 2022-08-19 10:38 a.m., Peter Zijlstra wrote:
> > On Thu, Aug 18, 2022 at 11:15:30AM -0700, kan.liang@...ux.intel.com wrote:
> >> From: Kan Liang <kan.liang@...ux.intel.com>
> >>
> >> For some Alder Lake N machine, the below unchecked MSR access error may be
> >> triggered.
> >>
> >> [ 0.088017] rcu: Hierarchical SRCU implementation.
> >> [ 0.088017] unchecked MSR access error: WRMSR to 0x38f (tried to write
> >> 0x0001000f0000003f) at rIP: 0xffffffffb5684de8 (native_write_msr+0x8/0x30)
> >> [ 0.088017] Call Trace:
> >> [ 0.088017] <TASK>
> >> [ 0.088017] __intel_pmu_enable_all.constprop.46+0x4a/0xa0
> > 
> > FWIW, I seem to get the same error when booting KVM on my ADL. I'm
> > fairly sure the whole CPUID vs vCPU thing is a trainwreck.
> 
> We will enhance the CPUID to address the issues. Hopefully, we can have
> them supported in the next generation.
> 

How about this?

---
[    0.170231] Performance Events: Alderlake Hybrid events, full-width counters, Intel PMU driver.
[    0.171420] core: hybrid PMU and virt are incompatible


 arch/x86/events/intel/core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 2db93498ff71..232e24324fd7 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -4473,6 +4473,11 @@ static bool init_hybrid_pmu(int cpu)
 	struct x86_hybrid_pmu *pmu = NULL;
 	int i;
 
+	if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
+		pr_warn_once("hybrid PMU and virt are incompatible\n");
+		return false;
+	}
+
 	if (!cpu_type && x86_pmu.get_hybrid_cpu_type)
 		cpu_type = x86_pmu.get_hybrid_cpu_type();