From: Sean Christopherson <seanjc@google.com>
To: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: 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-kernel@vger.kernel.org,
kvm@vger.kernel.org
Subject: Re: [RFC PATCH 2/2] KVM: VMX: Stop/resume host PT before/after VM entry when PT_MODE_HOST_GUEST
Date: Thu, 25 Aug 2022 15:34:48 +0000 [thread overview]
Message-ID: <YweWmF3wMPRnthIh@google.com> (raw)
In-Reply-To: <20220825085625.867763-3-xiaoyao.li@intel.com>
On Thu, Aug 25, 2022, Xiaoyao Li wrote:
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index d7f8331d6f7e..3e9ce8f600d2 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -38,6 +38,7 @@
> #include <asm/fpu/api.h>
> #include <asm/fpu/xstate.h>
> #include <asm/idtentry.h>
> +#include <asm/intel_pt.h>
> #include <asm/io.h>
> #include <asm/irq_remapping.h>
> #include <asm/kexec.h>
> @@ -1128,13 +1129,19 @@ static void pt_guest_enter(struct vcpu_vmx *vmx)
> if (vmx_pt_mode_is_system())
> return;
>
> + /*
> + * Stop Intel PT on host to avoid vm-entry failure since
> + * VM_ENTRY_LOAD_IA32_RTIT_CTL is set
> + */
> + intel_pt_stop();
> +
> /*
> * 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);
KVM's manual save/restore of MSR_IA32_RTIT_CTL should be dropped. If PT/RTIT can
trace post-VMXON, then intel_pt_stop() will disable tracing and intel_pt_resume()
will restore the host's desired value.
> if (vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN) {
> - wrmsrl(MSR_IA32_RTIT_CTL, 0);
> + /* intel_pt_stop() ensures RTIT_CTL.TraceEn is zero */
> pt_save_msr(&vmx->pt_desc.host, vmx->pt_desc.num_address_ranges);
Isn't this at risk of the same corruption? What prevents a PT NMI that arrives
after this point from changing other RTIT MSRs, thus causing KVM to restore the
wrong values?
> pt_load_msr(&vmx->pt_desc.guest, vmx->pt_desc.num_address_ranges);
> }
> @@ -1156,6 +1163,8 @@ static void pt_guest_exit(struct vcpu_vmx *vmx)
> */
> if (vmx->pt_desc.host.ctl)
> wrmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
> +
> + intel_pt_resume();
> }
>
> void vmx_set_host_fs_gs(struct vmcs_host_state *host, u16 fs_sel, u16 gs_sel,
> --
> 2.27.0
>
next prev parent reply other threads:[~2022-08-25 15:35 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 [this message]
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
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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