From: Sean Christopherson <seanjc@google.com>
To: "Wang, Wei W" <wei.w.wang@intel.com>
Cc: "Li, Xiaoyao" <xiaoyao.li@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
"linux-perf-users@vger.kernel.org"
<linux-perf-users@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [RFC PATCH 0/2] KVM: VMX: Fix VM entry failure on PT_MODE_HOST_GUEST while host is using PT
Date: Mon, 29 Aug 2022 17:33:42 +0000 [thread overview]
Message-ID: <Ywz4diMZBB7DdITb@google.com> (raw)
In-Reply-To: <CY5PR11MB6365897E8E6D0B590A298FA0DC769@CY5PR11MB6365.namprd11.prod.outlook.com>
On Mon, Aug 29, 2022, Wang, Wei W wrote:
> On Thursday, August 25, 2022 4:56 PM, Xiaoyao Li wrote:
> #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_AMD)
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index d7f8331d6f7e..195debc1bff1 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1125,37 +1125,29 @@ static inline void pt_save_msr(struct pt_ctx *ctx, u32 addr_range)
>
> static void pt_guest_enter(struct vcpu_vmx *vmx)
> {
> - if (vmx_pt_mode_is_system())
> + struct perf_event *event;
> +
> + if (vmx_pt_mode_is_system() ||
> + !(vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN))
I don't think the host should trace the guest in the host/guest mode just because
the guest isn't tracing itself. I.e. the host still needs to turn off it's own
tracing.
> return;
>
> - /*
> - * GUEST_IA32_RTIT_CTL is already set in the VMCS.
> - * Save host state before VM entry.
> - */
> - rdmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
> - if (vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN) {
> - wrmsrl(MSR_IA32_RTIT_CTL, 0);
> - pt_save_msr(&vmx->pt_desc.host, vmx->pt_desc.num_address_ranges);
> - pt_load_msr(&vmx->pt_desc.guest, vmx->pt_desc.num_address_ranges);
> - }
> + event = pt_get_curr_event();
> + perf_event_disable(event);
> + vmx->pt_desc.host_event = event;
This is effectively what I suggested[*], the main difference being that my version
adds dedicated enter/exit helpers so that perf can skip save/restore of the other
MSRs. It's easy to extend if perf needs to hand back an event to complete the "exit.
bool guest_trace_enabled = vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN;
vmx->pt_desc.host_event = intel_pt_guest_enter(guest_trace_enabled);
and then on exit
bool guest_trace_enabled = vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN;
intel_pt_guest_exit(vmx->pt_desc.host_event, guest_trace_enabled);
[*] https://lore.kernel.org/all/YwecducnM%2FU6tqJT@google.com
> + pt_load_msr(&vmx->pt_desc.guest, vmx->pt_desc.num_address_ranges);
> }
next prev parent reply other threads:[~2022-08-29 17:33 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-25 8:56 [RFC PATCH 0/2] KVM: VMX: Fix VM entry failure on PT_MODE_HOST_GUEST while host is using PT Xiaoyao Li
2022-08-25 8:56 ` [RFC PATCH 1/2] perf/x86/intel/pt: Introduce intel_pt_{stop,resume}() Xiaoyao Li
2022-08-25 15:23 ` Sean Christopherson
2022-08-25 8:56 ` [RFC PATCH 2/2] KVM: VMX: Stop/resume host PT before/after VM entry when PT_MODE_HOST_GUEST Xiaoyao Li
2022-08-25 15:34 ` Sean Christopherson
2022-08-25 15:45 ` Xiaoyao Li
2022-08-25 15:59 ` Sean Christopherson
2022-08-26 6:32 ` Xiaoyao Li
2022-08-26 15:08 ` Sean Christopherson
2022-08-29 7:49 ` [RFC PATCH 0/2] KVM: VMX: Fix VM entry failure on PT_MODE_HOST_GUEST while host is using PT Wang, Wei W
2022-08-29 17:33 ` Sean Christopherson [this message]
2022-08-30 6:02 ` Wang, Wei W
2022-09-08 7:25 ` Xiaoyao Li
2022-09-08 8:53 ` Wang, Wei W
2022-09-14 4:15 ` Xiaoyao Li
2022-09-14 6:16 ` Wang, Wei W
2022-09-14 20:25 ` Liang, Kan
2022-09-15 2:46 ` Wang, Wei W
2022-09-15 13:54 ` Liang, Kan
2022-09-15 14:39 ` Wang, Wei W
2022-09-15 15:42 ` Liang, Kan
2022-09-16 2:30 ` Wang, Wei W
2022-09-16 13:27 ` Liang, Kan
2022-09-19 13:46 ` Wang, Wei W
2022-09-19 14:41 ` Liang, Kan
2022-09-19 15:22 ` Wang, Wei W
2022-09-19 15:55 ` Liang, Kan
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