From: Sean Christopherson <seanjc@google.com>
To: Xin3 Li <xin3.li@intel.com>
Cc: Chao Gao <chao.gao@intel.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"linux-kselftest@vger.kernel.org"
<linux-kselftest@vger.kernel.org>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"corbet@lwn.net" <corbet@lwn.net>,
"kys@microsoft.com" <kys@microsoft.com>,
"haiyangz@microsoft.com" <haiyangz@microsoft.com>,
"wei.liu@kernel.org" <wei.liu@kernel.org>,
Dexuan Cui <decui@microsoft.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"bp@alien8.de" <bp@alien8.de>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"vkuznets@redhat.com" <vkuznets@redhat.com>,
"peterz@infradead.org" <peterz@infradead.org>,
Ravi V Shankar <ravi.v.shankar@intel.com>
Subject: Re: [PATCH v1 06/23] KVM: VMX: Defer enabling FRED MSRs save/load until after set CPUID
Date: Wed, 15 Nov 2023 13:47:39 -0800 [thread overview]
Message-ID: <ZVU8exa_l28ZbRsG@google.com> (raw)
In-Reply-To: <SA1PR11MB67345D35CE3FB950A0C90BDDA8B2A@SA1PR11MB6734.namprd11.prod.outlook.com>
On Tue, Nov 14, 2023, Xin3 Li wrote:
> > Implement what in a different way? The VMCS fields and FRED are architectural.
> > The internal layout of the VMCS is uarch specific, but the encodings and semantics
> > absolutely cannot change without breaking software. And if Intel does something
> > asinine like make a control active-low then we have far, far bigger problems.
>
> I should have made it clear that I wasn't talking at the ISA level. And
> of course CPU uarch implementations should be transparent to software.
>
> I mean a CPU uarch could choose to check the activation bit in the VM exit
> controls first and then decide whether to load the 2nd VM exit controls.
> While if resources allow, a CPU uarch could always load the 2nd VM exit
> controls.
And why does that matter? Loading a field speculatively/out-of-order is fine,
consuming it when it architecturally is supposed to be ignored is not.
next prev parent reply other threads:[~2023-11-15 21:47 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-08 18:29 [PATCH v1 00/23] Enable FRED with KVM VMX Xin Li
2023-11-08 18:29 ` [PATCH v1 01/23] KVM: VMX: Cleanup VMX basic information defines and usages Xin Li
2023-11-08 18:29 ` [PATCH v1 02/23] KVM: VMX: Cleanup VMX misc " Xin Li
2023-11-08 18:29 ` [PATCH v1 03/23] KVM: VMX: Add support for the secondary VM exit controls Xin Li
2023-11-08 18:29 ` [PATCH v1 04/23] KVM: x86: Mark CR4.FRED as not reserved Xin Li
2023-11-08 18:29 ` [PATCH v1 05/23] KVM: VMX: Initialize FRED VM entry/exit controls in vmcs_config Xin Li
2023-11-09 8:53 ` Chao Gao
2023-11-09 15:15 ` Sean Christopherson
2023-11-10 0:04 ` Li, Xin3
2023-11-10 15:01 ` Sean Christopherson
2023-11-14 4:05 ` Li, Xin3
2023-11-13 17:18 ` Nikolay Borisov
2023-11-15 2:39 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 06/23] KVM: VMX: Defer enabling FRED MSRs save/load until after set CPUID Xin Li
2023-11-09 9:15 ` Chao Gao
2023-11-09 23:50 ` Li, Xin3
2023-11-10 0:18 ` Sean Christopherson
2023-11-14 2:50 ` Li, Xin3
2023-11-15 21:47 ` Sean Christopherson [this message]
2023-11-08 18:29 ` [PATCH v1 07/23] KVM: VMX: Disable intercepting FRED MSRs Xin Li
2023-11-09 9:21 ` Chao Gao
2023-11-08 18:29 ` [PATCH v1 08/23] KVM: VMX: Initialize VMCS FRED fields Xin Li
2023-11-13 3:04 ` Chao Gao
2023-11-14 6:02 ` Li, Xin3
2023-11-14 6:51 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 09/23] KVM: VMX: Switch FRED RSP0 between host and guest Xin Li
2023-11-13 3:47 ` Chao Gao
2023-11-14 5:17 ` Li, Xin3
2023-11-14 7:47 ` Chao Gao
2023-11-15 3:04 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 10/23] KVM: VMX: Add support for FRED context save/restore Xin Li
2023-11-13 5:24 ` Chao Gao
2023-11-14 4:48 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 11/23] KVM: x86: Add kvm_is_fred_enabled() Xin Li
2023-11-13 7:35 ` Chao Gao
2023-11-14 4:42 ` Li, Xin3
2023-11-14 8:16 ` Chao Gao
2023-11-14 18:57 ` Li, Xin3
2023-11-20 9:04 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 12/23] KVM: VMX: Handle FRED event data Xin Li
2023-11-13 10:14 ` Chao Gao
2023-11-14 4:34 ` Li, Xin3
2023-11-14 8:58 ` Chao Gao
2023-11-15 2:52 ` Li, Xin3
2023-11-16 2:39 ` Chao Gao
2023-11-20 8:16 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 13/23] KVM: VMX: Handle VMX nested exception for FRED Xin Li
2023-11-14 7:40 ` Chao Gao
2023-11-15 3:03 ` Li, Xin3
2023-12-06 8:37 ` Li, Xin3
2023-12-07 8:42 ` Chao Gao
2023-12-07 10:09 ` Li, Xin3
2023-12-08 1:56 ` Chao Gao
2023-12-08 23:48 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 14/23] KVM: VMX: Dump FRED context in dump_vmcs() Xin Li
2023-11-14 14:36 ` Nikolay Borisov
2023-11-15 2:41 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 15/23] KVM: nVMX: Add support for the secondary VM exit controls Xin Li
2023-11-09 8:21 ` Jeremi Piotrowski
2023-11-10 0:12 ` Li, Xin3
2023-11-20 15:52 ` Vitaly Kuznetsov
2023-11-20 17:42 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 16/23] KVM: nVMX: Add FRED VMCS fields Xin Li
2023-11-08 18:29 ` [PATCH v1 17/23] KVM: nVMX: Add support for VMX FRED controls Xin Li
2023-11-08 18:29 ` [PATCH v1 18/23] KVM: nVMX: Add VMCS FRED states checking Xin Li
2023-11-08 18:29 ` [PATCH v1 19/23] KVM: x86: Allow FRED/LKGS/WRMSRNS to be exposed to guests Xin Li
2023-11-08 18:30 ` [PATCH v1 20/23] KVM: selftests: Add FRED VMCS fields to evmcs Xin Li
2023-11-08 18:30 ` [PATCH v1 21/23] KVM: selftests: Run debug_regs test with FRED enabled Xin Li
2023-11-08 18:30 ` [PATCH v1 22/23] KVM: selftests: Add a new VM guest mode to run user level code Xin Li
2023-11-08 18:30 ` [PATCH v1 23/23] KVM: selftests: Add fred exception tests Xin Li
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