From: Binbin Wu <binbin.wu@linux.intel.com>
To: Sohil Mehta <sohil.mehta@intel.com>
Cc: kvm@vger.kernel.org, x86@kernel.org,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H . Peter Anvin" <hpa@zytor.com>, Shuah Khan <shuah@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"Chang S . Bae" <chang.seok.bae@intel.com>,
Kai Huang <kai.huang@intel.com>,
Fuad Tabba <fuad.tabba@linux.dev>, Chao Gao <chao.gao@intel.com>,
Yosry Ahmed <yosry@kernel.org>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
David Matlack <dmatlack@google.com>,
Bala-Vignesh-Reddy <reddybalavignesh9979@gmail.com>,
Kishen Maloor <kishen.maloor@intel.com>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v4 5/7] KVM: x86: Virtualize LASS and advertise support to userspace
Date: Wed, 19 Aug 2026 17:01:30 +0800 [thread overview]
Message-ID: <481a39fa-d99f-4139-823b-1d9327c3a9c8@linux.intel.com> (raw)
In-Reply-To: <20260806011536.4172258-6-sohil.mehta@intel.com>
On 8/6/2026 9:15 AM, Sohil Mehta wrote:
> From: Zeng Guang <guang.zeng@intel.com>
>
> Virtualize Linear Address Space Separation (LASS) by letting the guest
> enable CR4.LASS[bit 27]. Allow the guest to set CR4.LASS only if LASS is
> enumerated in the guest's CPUID. Set CR4.LASS in the emulated
> IA32_VMX_CR4_FIXED1 MSR so that LASS can be enabled in nested VMX
> operation as well.
>
> Keep CR4.LASS KVM-owned instead of making it guest-owned. LASS is
> expected to be enabled once per vCPU at boot and rarely toggled at
> runtime.
>
> LASS is enumerated by CPUID.(EAX=07H,ECX=1):EAX.LASS[bit 6] and only
> works in IA-32e mode. Advertise LASS to userspace on 64-bit kernels and
> only when it is supported by the host. Notably, it will not be exposed
> to userspace if the deprecated vsyscall=emulate mode is set on the
^
Nit: mode could be dropped.
> kernel command line.
>
> Signed-off-by: Zeng Guang <guang.zeng@intel.com>
> Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
> Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
next prev parent reply other threads:[~2026-08-19 9:01 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-06 1:15 [PATCH v4 0/7] KVM: x86: Add LASS virtualization support Sohil Mehta
2026-08-06 1:15 ` [PATCH v4 1/7] KVM: x86: Add an emulator flag to differentiate branch targets from fetches Sohil Mehta
2026-08-06 1:15 ` [PATCH v4 2/7] KVM: x86: Use linear_read_system() to read the TSS I/O bitmap Sohil Mehta
2026-08-19 3:19 ` Binbin Wu
2026-08-19 5:03 ` Sohil Mehta
2026-08-19 5:21 ` H. Peter Anvin
2026-08-19 5:26 ` Binbin Wu
2026-08-06 1:15 ` [PATCH v4 3/7] KVM: x86: Add LASS violation checks during instruction emulation Sohil Mehta
2026-08-19 5:58 ` Binbin Wu
2026-08-06 1:15 ` [PATCH v4 4/7] KVM: VMX: Implement LASS violation check Sohil Mehta
2026-08-19 8:49 ` Binbin Wu
2026-08-06 1:15 ` [PATCH v4 5/7] KVM: x86: Virtualize LASS and advertise support to userspace Sohil Mehta
2026-08-19 9:01 ` Binbin Wu [this message]
2026-08-06 1:15 ` [PATCH v4 6/7] KVM: selftests: Add coverage for LASS CPUID and CR4 handling Sohil Mehta
2026-08-06 1:15 ` [PATCH v4 7/7] selftests/x86: Add a userspace test for LASS enforcement Sohil Mehta
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