linux-kernel - Re: [RFC/RFT PATCH 0/2] x86: sgx_vepc: implement ioctl to EREMOVE all pages

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Message-ID: <b87fbe2fe213976fa43fb82d5d483da8e6b1bc63.camel@kernel.org>
Date:   Tue, 14 Sep 2021 20:40:41 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Yang Zhong <yang.zhong@...el.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org, dave.hansen@...ux.intel.com
Subject: Re: [RFC/RFT PATCH 0/2] x86: sgx_vepc: implement ioctl to EREMOVE
 all pages

On Tue, 2021-09-14 at 19:07 +0200, Paolo Bonzini wrote:
> On 14/09/21 18:42, Jarkko Sakkinen wrote:
> > > Let's wait for this patch to be accepted first.  I'll wait a little more
> > > for Jarkko and Dave to comment on this, and include your "Tested-by".
> > > 
> > > I will also add cond_resched() on the final submission.
> > Why these would be conflicting tasks? I.e. why could not QEMU use
> > what is available now and move forward using better mechanism, when
> > they are available?
> 
> The implementation using close/open is quite ugly (destroying and 
> recreating the memory block breaks a few levels of abstractions), so 
> it's not really something I'd like to commit.

OK, so the driving reason for SGX_IOC_VEPC_RESET is the complex dance
with opening, closing and mmapping() stuff, especially when dealing
with multiple sections for one VM? OK, I think I can understand this,
given how notorious it might be to get stable in the user space.

Please just document this use case some way (if I got it right) to
the commit message of the next version, and I think this starts to
make much more sense.

/Jarkko