From: "Xing, Cedric" <cedric.xing@intel.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Jethro Beekman <jethro@fortanix.com>,
Dave Hansen <dave.hansen@intel.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
linux-sgx@vger.kernel.org, x86@kernel.org,
Haitao Huang <haitao.huang@linux.intel.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH] x86/vdso: Remove retpoline from SGX vDSO call
Date: Wed, 30 Sep 2020 13:45:52 -0700 [thread overview]
Message-ID: <741b45d0-3833-4e5d-5974-81634d1b55eb@intel.com> (raw)
In-Reply-To: <20200930192541.GA60658@linux.intel.com>
On 9/30/2020 12:25 PM, Jarkko Sakkinen wrote:
> On Wed, Sep 30, 2020 at 07:09:33PM +0100, Andrew Cooper wrote:
>> Honestly, my advice would be to leave it unprotected for now. Anyone
>> who managed to figure out the rest of the practical userspace issues
>> will probably have a much better idea of what can/should be done in this
>> case.
>>
>> If that doesn't sit well with people, then the next best would probably
>> be LFENCE; CALL *reg/mem; LFENCE to cover as many of the corner cases as
>> possible without being incompatible with CET. Its not as if this
>> callback is the slow aspect of entering/exiting SGX mode.
>>
>> ~Andrew
>
> I tend to agree. We cannot drive changes based on unknown unknowns.
>
> And I don't see why we could not add boot time patching of retpoline
> even after the code is in the mainline kernel, if something ever
> pushes to that direction.
>
> /Jarkko
>
I agree. It'll be compatible with CET. The overhead of LFENCE is
negligible comparing to entering/exiting SGX mode.
next prev parent reply other threads:[~2020-09-30 20:46 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-30 14:01 [PATCH] x86/vdso: Remove retpoline from SGX vDSO call Jarkko Sakkinen
2020-09-30 14:08 ` Dave Hansen
2020-09-30 14:20 ` Jarkko Sakkinen
2020-09-30 14:33 ` Dave Hansen
2020-09-30 15:28 ` Jarkko Sakkinen
2020-09-30 15:43 ` Sean Christopherson
2020-09-30 16:28 ` Dave Hansen
2020-09-30 17:01 ` Jethro Beekman
2020-09-30 18:09 ` Andrew Cooper
2020-09-30 19:25 ` Jarkko Sakkinen
2020-09-30 20:45 ` Xing, Cedric [this message]
2020-09-30 21:22 ` Jarkko Sakkinen
2020-09-30 21:36 ` Jarkko Sakkinen
2020-09-30 21:46 ` Dave Hansen
2020-09-30 23:41 ` Jarkko Sakkinen
2020-09-30 16:38 ` Jarkko Sakkinen
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