linux-kernel - Re: [PATCH 02/25] x86/cpufeatures: Add SGX1 and SGX2 sub-features

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Date:   Tue, 02 Mar 2021 18:53:59 +0100
From:   Boris Petkov <bp@...en8.de>
To:     Sean Christopherson <seanjc@...gle.com>,
        Kai Huang <kai.huang@...el.com>
CC:     kvm@...r.kernel.org, x86@...nel.org, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org, jarkko@...nel.org, luto@...nel.org,
        dave.hansen@...el.com, rick.p.edgecombe@...el.com,
        haitao.huang@...el.com, pbonzini@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com
Subject: Re: [PATCH 02/25] x86/cpufeatures: Add SGX1 and SGX2 sub-features

On March 2, 2021 5:02:13 PM GMT+01:00, Sean Christopherson <seanjc@...gle.com> wrote:
>The KVM use case is to query /proc/cpuinfo to see if sgx2 can be
>enabled in a
>guest.

You mean before the guest ia created? I sure hope there's a better way to query HV-supported features than grepping /proc/cpuinfo...

>The counter-argument to that is we might want sgx2 in /proc/cpuinfo to
>mean sgx2
>is enabled in hardware _and_ supported by the kernel.  Userspace can
>grep for
>sgx in /proc/cpuinfo, and use cpuid to discover sgx2, so it's not a
>blocker.

Question is, what exactly that flag should denote: that EDMM is supported in the HV and guests can do the dynamic thing of adding/rwmoving EPC pages? Is that the only feature behind SGX2?

>That being said, adding some form of capability/versioning to SGX seems
>inevitable, not sure it's worth witholding sgx2 from /proc/cpuinfo.

See what I typed earlier - no objections from me if a proper use case is identified and written down.

Thx.
-- 
Sent from a small device: formatting sux and brevity is inevitable.