From: Paolo Bonzini <pbonzini@redhat.com>
To: Jon Kohler <jon@nutanix.com>,
seanjc@google.com, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org,
hpa@zytor.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Jonathan Corbet <corbet@lwn.net>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>
Cc: ken@codelabs.ch, Alexander.Grest@microsoft.com,
chao.gao@intel.com, madvenka@linux.microsoft.com,
mic@digikod.net, nsaenz@amazon.es, tao1.su@linux.intel.com,
xiaoyao.li@intel.com, zhao1.liu@intel.com
Subject: Re: [PATCH 5/8] KVM: x86/mmu: bootstrap support for Intel MBEC
Date: Tue, 3 Mar 2026 18:54:04 +0100 [thread overview]
Message-ID: <4a4bd216-3cdf-4098-8a59-a4cbceb31677@redhat.com> (raw)
In-Reply-To: <20251223054806.1611168-6-jon@nutanix.com>
On 12/23/25 06:47, Jon Kohler wrote:
> Extend kvm_mmu_page_role access bitfield from 3 to 4, where the 4th bit
> will be used to track user executable pages with Intel mode-based
> execute control (MBEC).
>
> Extend SPTE generation and introduce shadow_ux value to account for
> user and kernel executable distinctions under MBEC.
While MBEC has a different definition of the bits, GMET is essentially
SMEP (except that AMD couldn't retrofit it into hCR4.SMEP due to how NPT
handles the U bit). I wonder if it's possible to handle MBEC as SMEP as
well, with some additional handling of the SPTEs (with shadox_x_mask and
shadow_ux_mask taking the functionality of shadow_nx_mask and
shadow_u_mask) but no large changes to the MMU.
This should be a much simpler patch set if it can be made to work. I'll
take a look.
Paolo
next prev parent reply other threads:[~2026-03-03 17:54 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-23 5:47 [PATCH 0/8] KVM: VMX: Introduce Intel Mode-Based Execute Control (MBEC) Jon Kohler
2025-12-23 5:47 ` [PATCH 1/8] KVM: TDX/VMX: rework EPT_VIOLATION_EXEC_FOR_RING3_LIN into PROT_MASK Jon Kohler
2025-12-23 5:47 ` [PATCH 2/8] KVM: x86/mmu: remove SPTE_PERM_MASK Jon Kohler
2025-12-23 5:47 ` [PATCH 3/8] KVM: x86/mmu: adjust MMIO generation bit allocation and allowed mask Jon Kohler
2025-12-23 5:47 ` [PATCH 4/8] KVM: x86/mmu: update access permissions from ACC_ALL to ACC_RWX Jon Kohler
2025-12-23 5:47 ` [PATCH 5/8] KVM: x86/mmu: bootstrap support for Intel MBEC Jon Kohler
2026-03-03 17:54 ` Paolo Bonzini [this message]
2026-03-03 19:04 ` Jon Kohler
2025-12-23 5:47 ` [PATCH 6/8] KVM: VMX: enhance EPT violation handler for MBEC Jon Kohler
2025-12-23 5:48 ` [PATCH 7/8] KVM: VMX: allow MBEC with EVMCS Jon Kohler
2025-12-23 5:48 ` [PATCH 8/8] KVM: nVMX: advertise MBEC and setup mmu has_mbec Jon Kohler
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