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[66.57.248.11]) by smtp.googlemail.com with ESMTPSA id o2-20020ac87c42000000b0035cebb79aaesm15016302qtv.18.2022.10.05.05.04.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Oct 2022 05:04:10 -0700 (PDT) Message-ID: Date: Wed, 5 Oct 2022 14:04:09 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.1 Subject: Re: Finish removing MPX from arch/x86? Content-Language: en-US To: Dave Hansen , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Arjan van de Ven References: <547a1203-0339-7ad2-9505-eab027046298@intel.com> From: Paolo Bonzini In-Reply-To: <547a1203-0339-7ad2-9505-eab027046298@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/4/22 19:34, Dave Hansen wrote: > We zapped the userspace MPX ABIs and most of its supporting code in here: > > 45fc24e89b7c ("x86/mpx: remove MPX from arch/x86") > > But, the XSAVE enabling and KVM code were left in place. This let folks > at least keep running guests with MPX. > > It's been a couple of years and I don't think I've had a single person > opine about the loss of MPX. Intel also followed through and there's no > MPX to be found on newer CPUs like my "Tiger Lake" 11th Gen Intel(R) > Core(TM) i7-1165G7. > > Is it time to zap MPX from arch/x86/kvm/? I agree that the likelihood of anybody complaining about MPX is low but Jim is right that the timeline for removing it is unfortunately quite long. Removing MPX from XFEATURE_MASK_USER_SUPPORTED is possible, though we need to add a new XFEATURE_MASK_GUEST_SUPPORTED that includes MPX. I'll take a look. Also, it's worth noting that MPX lives in the sigcontext ABI because it uses the non-compacted format. Because of that it is not possible to remove the structs from include/asm/fpu/types.h, for example. Paolo