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Date:   Thu, 13 Jun 2019 12:15:59 -0700
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     Andy Lutomirski <luto@kernel.org>
Cc:     Jethro Beekman <jethro@fortanix.com>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Cedric Xing <cedric.xing@intel.com>,
        "Dr . Greg Wettstein" <greg@enjellic.com>
Subject: Re: [PATCH 4/7] x86/sgx: Allow userspace to add multiple pages in
 single ioctl()
Message-ID: <20190613191559.GA18385@linux.intel.com>
References: <20190605194845.926-1-sean.j.christopherson@intel.com>
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On Thu, Jun 13, 2019 at 12:05:37PM -0700, Andy Lutomirski wrote:
> On Thu, Jun 13, 2019 at 9:51 AM Sean Christopherson
> <sean.j.christopherson@intel.com> wrote:
> > If we ditch the workqueue then we probably don't even need to gift the
> > page, e.g. I think we allocate the EPC page prior to taking mmap_sem, and
> > then simply do gup+kmap around EADD.  We'd just need to be careful about
> > not allocating EPC pages for ioctls that are guaranteed to fail.
> >
> >
> 
> Why gup + kmap?  Can't you just do STAC; EADD; CLAC?  (Using the
> appropriate C helpers, of course.)

That should work as well, we already have exception fixup on ENCLS.  I
obviously haven't given much thought to what all we can do once the
workqueue goes bye bye :-)