linux-kernel - Re: [RFC PATCH v2 09/10] x86/cpu: Call ENCLS[EUPDATESVN] procedure in microcode update

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Date:   Fri, 18 Mar 2022 10:06:25 +0100
From:   Jethro Beekman <jethro@...tanix.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        Cathy Zhang <cathy.zhang@...el.com>, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     ashok.raj@...el.com
Subject: Re: [RFC PATCH v2 09/10] x86/cpu: Call ENCLS[EUPDATESVN] procedure in
 microcode update

On 2022-03-16 16:47, Dave Hansen wrote:
> On 3/16/22 03:24, Jethro Beekman wrote:
>>> Doing this automatically and unconditionally during a microcode
>>> update seems undesirable. This requires the userland tooling that
>>> is coordinating the microcode update to be aware of any SGX
>>> enclaves that are running and possibly coordinate sequencing with
>>> the processes containing those enclaves. This coupling does not
>>> exist today.
>> Also, a microcode update may not affect SGX security at all and doing
>> the EUPDATESVN procedure may not be required for this particular
>> update. This case is called out specifically in the EUPDATESVN
>> documentation.
> 
> I don't think Intel provides the metadata for the kernel to tell if an
> update requires an EUPDATESVN procedure or not.  If this is inconvenient
> for you, I'd suggest reporting this to the folks at Intel who can fix
> it.  It doesn't seem like something which they are motivated to fix.

Whether or not metadata is currently made available is orthogonal to creating a mechanism by which userspace can indidate that a particular microcode update shouldn't trigger the EUPDATESVN procedure.

--
Jethro Beekman | Fortanix

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