From: Sean Christopherson <seanjc@google.com>
To: "Xin Li (Intel)" <xin@zytor.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, pbonzini@redhat.com, corbet@lwn.net,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
luto@kernel.org, peterz@infradead.org,
andrew.cooper3@citrix.com
Subject: Re: [PATCH v3 20/27] KVM: x86: Allow WRMSRNS to be advertised to guests
Date: Tue, 25 Feb 2025 07:41:13 -0800 [thread overview]
Message-ID: <Z73kmRwZFJJAVkiZ@google.com> (raw)
In-Reply-To: <20241001050110.3643764-21-xin@zytor.com>
On Mon, Sep 30, 2024, Xin Li (Intel) wrote:
> From: Xin Li <xin3.li@intel.com>
>
> Allow WRMSRNS to be advertised to guests.
The shortlog and this sentence are incorrect. Assuming there are no controls for
WRMSRNS, then KVM isn't allowing anything. Userspace can advertise WRMSRNS support
whenever it wants, and the guest can cleanly execute WRMSRNS regardless of whether
or not it's advertised in CPUID. KVM is simply advertising support to userspace.
> WRMSRNS behaves exactly like WRMSR with the only difference being
Nope, not the only difference.
WRMSR and WRMSRNS use the same basic exit reason (see Appendix C). For WRMSR,
the exit qualification is 0, while for WRMSRNS it is 1.
And the whole reaosn I went spelunking was to verify that WRMSRNS honors all MSR
exiting controls and generates the same exits. That information needs to be
explicitly stated.
I'll rewrite the shortlog and changelog when applying.
next prev parent reply other threads:[~2025-02-25 15:41 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-01 5:00 [PATCH v3 00/27] Enable FRED with KVM VMX Xin Li (Intel)
2024-10-01 5:00 ` [PATCH v3 01/27] KVM: x86: Use a dedicated flow for queueing re-injected exceptions Xin Li (Intel)
2024-10-01 5:00 ` [PATCH v3 02/27] KVM: VMX: Don't modify guest XFD_ERR if CR0.TS=1 Xin Li (Intel)
2024-10-01 5:00 ` [PATCH v3 03/27] KVM: VMX: Add support for the secondary VM exit controls Xin Li (Intel)
2024-10-21 8:28 ` Chao Gao
2024-10-21 17:03 ` Xin Li
2024-10-22 2:47 ` Chao Gao
2024-10-22 16:30 ` Xin Li
2025-02-25 17:28 ` Sean Christopherson
2024-10-01 5:00 ` [PATCH v3 04/27] KVM: VMX: Initialize FRED VM entry/exit controls in vmcs_config Xin Li (Intel)
2024-10-01 5:00 ` [PATCH v3 05/27] KVM: VMX: Disable FRED if FRED consistency checks fail Xin Li (Intel)
2024-10-22 8:48 ` Chao Gao
2024-10-22 16:21 ` Xin Li
2024-11-26 15:32 ` Borislav Petkov
2024-11-26 18:53 ` Xin Li
2024-11-26 19:04 ` Borislav Petkov
2024-10-01 5:00 ` [PATCH v3 06/27] x86/cea: Export per CPU variable cea_exception_stacks Xin Li (Intel)
2024-10-01 16:12 ` Dave Hansen
2024-10-01 17:51 ` Xin Li
2024-10-01 18:18 ` Dave Hansen
2024-10-01 5:00 ` [PATCH v3 07/27] KVM: VMX: Initialize VMCS FRED fields Xin Li (Intel)
2024-10-22 9:06 ` Chao Gao
2024-10-22 16:18 ` Xin Li
2024-10-01 5:00 ` [PATCH v3 08/27] KVM: x86: Use KVM-governed feature framework to track "FRED enabled" Xin Li (Intel)
2024-10-01 5:00 ` [PATCH v3 09/27] KVM: VMX: Do not use MAX_POSSIBLE_PASSTHROUGH_MSRS in array definition Xin Li (Intel)
2024-11-26 18:02 ` Borislav Petkov
2024-11-26 19:22 ` Xin Li
2024-11-26 20:06 ` Borislav Petkov
2024-11-27 6:46 ` Xin Li
2024-11-27 6:55 ` Borislav Petkov
2024-11-27 7:02 ` Xin Li
2024-11-27 7:10 ` Borislav Petkov
2024-11-27 7:32 ` Xin Li
2024-11-27 7:58 ` Borislav Petkov
2024-10-01 5:00 ` [PATCH v3 10/27] KVM: VMX: Set FRED MSR interception Xin Li (Intel)
2024-11-13 11:31 ` Chao Gao
2024-10-01 5:00 ` [PATCH v3 11/27] KVM: VMX: Save/restore guest FRED RSP0 Xin Li (Intel)
2024-10-01 5:00 ` [PATCH v3 12/27] KVM: VMX: Add support for FRED context save/restore Xin Li (Intel)
2024-10-01 5:00 ` [PATCH v3 13/27] KVM: x86: Add a helper to detect if FRED is enabled for a vCPU Xin Li (Intel)
2024-10-01 5:00 ` [PATCH v3 14/27] KVM: VMX: Pass XFD_ERR as pseudo-payload when injecting #NM Xin Li (Intel)
2024-10-01 5:00 ` [PATCH v3 15/27] KVM: VMX: Virtualize FRED event_data Xin Li (Intel)
2024-10-01 5:00 ` [PATCH v3 16/27] KVM: VMX: Virtualize FRED nested exception tracking Xin Li (Intel)
2024-10-24 6:24 ` Chao Gao
2024-10-25 8:04 ` Xin Li
2024-10-28 6:33 ` Chao Gao
2024-12-05 7:16 ` Xin Li
2024-10-01 5:01 ` [PATCH v3 17/27] KVM: x86: Mark CR4.FRED as not reserved when guest can use FRED Xin Li (Intel)
2024-10-24 7:18 ` Chao Gao
2024-12-12 18:48 ` Xin Li
2024-12-12 19:05 ` Sean Christopherson
2024-12-13 18:43 ` Xin Li
2024-10-01 5:01 ` [PATCH v3 18/27] KVM: VMX: Dump FRED context in dump_vmcs() Xin Li (Intel)
2024-10-24 7:23 ` Chao Gao
2024-10-24 16:50 ` Xin Li
2024-10-01 5:01 ` [PATCH v3 19/27] KVM: x86: Allow FRED/LKGS to be advertised to guests Xin Li (Intel)
2024-10-01 5:01 ` [PATCH v3 20/27] KVM: x86: Allow WRMSRNS " Xin Li (Intel)
2025-02-25 15:41 ` Sean Christopherson [this message]
2024-10-01 5:01 ` [PATCH v3 21/27] KVM: VMX: Invoke vmx_set_cpu_caps() before nested setup Xin Li (Intel)
2024-10-24 7:49 ` Chao Gao
2024-10-25 7:34 ` Xin Li
2025-02-25 16:01 ` Sean Christopherson
2024-10-01 5:01 ` [PATCH v3 22/27] KVM: nVMX: Add support for the secondary VM exit controls Xin Li (Intel)
2024-10-01 5:01 ` [PATCH v3 23/27] KVM: nVMX: Add a prerequisite to SHADOW_FIELD_R[OW] macros Xin Li (Intel)
2024-10-01 5:01 ` [PATCH v3 24/27] KVM: nVMX: Add a prerequisite to existence of VMCS fields Xin Li (Intel)
2025-02-25 16:22 ` Sean Christopherson
2025-02-25 16:37 ` Xin Li
2025-02-25 19:32 ` Sean Christopherson
2024-10-01 5:01 ` [PATCH v3 25/27] KVM: nVMX: Add FRED " Xin Li (Intel)
2024-10-24 7:42 ` Chao Gao
2024-10-25 7:25 ` Xin Li
2024-10-28 9:07 ` Chao Gao
2024-10-28 18:27 ` Sean Christopherson
2024-10-29 17:40 ` Xin Li
2024-10-01 5:01 ` [PATCH v3 26/27] KVM: nVMX: Add VMCS FRED states checking Xin Li (Intel)
2024-10-01 5:01 ` [PATCH v3 27/27] KVM: nVMX: Allow VMX FRED controls Xin Li (Intel)
2025-02-19 0:26 ` [PATCH v3 00/27] Enable FRED with KVM VMX Xin Li
2025-02-25 15:24 ` Sean Christopherson
2025-02-25 17:04 ` Xin Li
2025-02-25 17:35 ` Sean Christopherson
2025-02-25 18:48 ` Xin Li
2025-02-28 17:06 ` Sean Christopherson
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