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Tue, 03 Mar 2026 09:54:09 -0800 (PST) Received: from [192.168.10.81] ([151.95.144.138]) by smtp.googlemail.com with ESMTPSA id 5b1f17b1804b1-483bd68826asm797166665e9.0.2026.03.03.09.54.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Mar 2026 09:54:09 -0800 (PST) Message-ID: <4a4bd216-3cdf-4098-8a59-a4cbceb31677@redhat.com> Date: Tue, 3 Mar 2026 18:54:04 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5/8] KVM: x86/mmu: bootstrap support for Intel MBEC To: Jon Kohler , 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 , "open list:DOCUMENTATION" 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 References: <20251223054806.1611168-1-jon@nutanix.com> <20251223054806.1611168-6-jon@nutanix.com> From: Paolo Bonzini Content-Language: en-US In-Reply-To: <20251223054806.1611168-6-jon@nutanix.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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