From: Sohil Mehta <sohil.mehta@intel.com>
To: Sean Christopherson <seanjc@google.com>,
"H. Peter Anvin" <hpa@zytor.com>
Cc: Xin Li <xin@zytor.com>, <kvm@vger.kernel.org>, <x86@kernel.org>,
"Paolo Bonzini" <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Shuah Khan <skhan@linuxfoundation.org>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
"Peter Zijlstra" <peterz@infradead.org>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Nikunj A Dadhania <nikunj@amd.com>,
Shivansh Dhiman <shivansh.dhiman@amd.com>,
David Woodhouse <dwmw@amazon.co.uk>,
Chao Gao <chao.gao@intel.com>,
Binbin Wu <binbin.wu@linux.intel.com>,
Zhao Liu <zhao1.liu@intel.com>, Yosry Ahmed <yosry@kernel.org>,
David Matlack <dmatlack@google.com>, <linux-doc@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH v10 00/28] KVM: Enable FRED support with KVM VMX
Date: Mon, 26 Oct 2026 15:22:32 -0700 [thread overview]
Message-ID: <dd5fa920-2ac6-41c9-a86a-11d5ad929b34@intel.com> (raw)
In-Reply-To: <20d0feae-9aa0-43cf-8357-fcdf617a5a97@intel.com>
On 10/26/2026 10:22 AM, Sohil Mehta wrote:
> On 10/26/2026 9:04 AM, Sean Christopherson wrote:
>
>> And we'd want to keep the optimizations to elide writes when vCPUs are using the
>> same value(s). So, compile tested only...
>>
>
> Will test this out on real hardware with the MSR_STAR change below.
>
With MSR_STAR not restored (original patch), the kernel boots fine, but
a guest's STAR stays loaded and it triggers a ERETS #GP as expected when
CS/SS has a mismatch.
With MSR_STAR dropped from kvm_is_msr_used_in_host(), it works as
expected. x86 KVM selftests pass and the systems runs without issues.
A few AI generated scripts and tests confirmed that STAR is restored
each time and LSTAR/SYSCALL_MASK is left at the guest's values when FRED
is enabled. Also, SYSCALL in each guest still lands on its own LSTAR
when two VMs alternate on one pCPU.
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
next prev parent reply other threads:[~2026-10-26 22:22 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-11 21:36 [PATCH v10 00/28] KVM: Enable FRED support with KVM VMX Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 01/28] KVM: VMX: Enable support for secondary VM exit controls Sohil Mehta
2026-10-22 9:27 ` Binbin Wu
2026-10-23 2:09 ` Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 02/28] KVM: VMX: Initialize VM entry/exit FRED controls in vmcs_config Sohil Mehta
2026-10-22 9:48 ` Binbin Wu
2026-10-23 3:10 ` Sohil Mehta
2026-10-26 5:00 ` Sohil Mehta
2026-10-27 1:25 ` Binbin Wu
2026-09-11 21:36 ` [PATCH v10 03/28] KVM: VMX: Disable FRED if FRED consistency checks fail Sohil Mehta
2026-10-22 10:19 ` Binbin Wu
2026-10-23 3:13 ` Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 04/28] x86/cea: Prefix event stack names with ESTACK_ Sohil Mehta
2026-10-23 5:58 ` Binbin Wu
2026-09-11 21:36 ` [PATCH v10 05/28] x86/cea: Use array indexing to simplify exception stack access Sohil Mehta
2026-10-23 6:07 ` Binbin Wu
2026-09-11 21:36 ` [PATCH v10 06/28] x86/fred: Export this_cpu_fred_rsp() for KVM usage Sohil Mehta
2026-10-23 6:49 ` Binbin Wu
2026-09-11 21:36 ` [PATCH v10 07/28] KVM: VMX: Initialize VMCS FRED fields Sohil Mehta
2026-10-23 7:19 ` Binbin Wu
2026-09-11 21:36 ` [PATCH v10 08/28] KVM: VMX: Set FRED MSR intercepts Sohil Mehta
2026-10-23 8:07 ` Binbin Wu
2026-09-11 21:36 ` [PATCH v10 09/28] KVM: VMX: Save/restore guest FRED RSP0 Sohil Mehta
2026-09-14 7:04 ` Binbin Wu
2026-09-14 16:14 ` Edgecombe, Rick P
2026-09-15 8:43 ` Binbin Wu
2026-09-11 21:36 ` [PATCH v10 10/28] KVM: VMX: Add support for saving and restoring FRED MSRs Sohil Mehta
2026-10-23 8:59 ` Binbin Wu
2026-09-11 21:36 ` [PATCH v10 11/28] KVM: x86: Add a helper to detect if FRED is enabled for a vCPU Sohil Mehta
2026-10-23 9:21 ` Binbin Wu
2026-09-11 21:36 ` [PATCH v10 12/28] KVM: x86: Add a new save/restore flag for FRED metadata Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 13/28] KVM: VMX: Virtualize FRED nested exception tracking Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 14/28] KVM: VMX: Virtualize FRED event_data Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 15/28] KVM: x86: Include CR4.FRED in the emulator CR4 write mask Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 16/28] KVM: x86: Mark CR4.FRED as not reserved Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 17/28] KVM: x86: Handle CR4.FRED when emulating RSM Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 18/28] KVM: VMX: Dump FRED context in dump_vmcs() Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 19/28] KVM: x86: Advertise support for FRED Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 20/28] KVM: nVMX: Enable support for secondary VM exit controls Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 21/28] KVM: nVMX: Handle FRED VMCS fields in nested VMX context Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 22/28] KVM: nVMX: Restrict event data VMCS fields to FRED-supported hosts Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 23/28] KVM: nVMX: Shadow ORIGINAL_EVENT_DATA and INJECTED_EVENT_DATA fields Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 24/28] KVM: nVMX: Validate FRED-related VMCS fields Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 25/28] KVM: nVMX: Enable VMX FRED controls Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 26/28] KVM: selftests: Add FRED MSRs to msrs_test Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 27/28] KVM: selftests: Add a new VM guest mode to run user level code Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 28/28] KVM: selftests: Add fred exception tests Sohil Mehta
2026-09-15 6:03 ` [PATCH v10 00/28] KVM: Enable FRED support with KVM VMX Xin Li
2026-10-24 22:59 ` H. Peter Anvin
2026-10-26 16:04 ` Sean Christopherson
2026-10-26 17:22 ` Sohil Mehta
2026-10-26 22:22 ` Sohil Mehta [this message]
2026-09-15 10:00 ` [EXTERNAL] " David Woodhouse
2026-09-24 11:14 ` Shivansh Dhiman
2026-09-24 14:13 ` David Woodhouse
2026-09-25 12:06 ` Shivansh Dhiman
2026-10-19 20:46 ` Dave Hansen
2026-10-19 22:19 ` Sohil Mehta
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