linux-kernel - Re: [PATCH v24 12/24] x86/sgx: Linux Enclave Driver

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Message-ID: <20191202182102.GF4063@linux.intel.com>
Date:   Mon, 2 Dec 2019 10:21:03 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Haitao Huang <haitao.huang@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        akpm@...ux-foundation.org, dave.hansen@...el.com,
        nhorman@...hat.com, npmccallum@...hat.com, serge.ayoun@...el.com,
        shay.katz-zamir@...el.com, haitao.huang@...el.com,
        andriy.shevchenko@...ux.intel.com, tglx@...utronix.de,
        kai.svahn@...el.com, bp@...en8.de, josh@...htriplett.org,
        luto@...nel.org, kai.huang@...el.com, rientjes@...gle.com,
        cedric.xing@...el.com, puiterwijk@...hat.com,
        linux-security-module@...r.kernel.org,
        Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [PATCH v24 12/24] x86/sgx: Linux Enclave Driver

On Mon, Dec 02, 2019 at 09:48:43AM -0600, Haitao Huang wrote:
> On Fri, 29 Nov 2019 17:13:14 -0600, Jarkko Sakkinen
> <jarkko.sakkinen@...ux.intel.com> wrote:
> 
> 
> >+
> >+	for (c = 0 ; c < addp.length; c += PAGE_SIZE) {
> >+		if (signal_pending(current)) {
> >+			ret = -ERESTARTSYS;
> >+			break;
> >+		}
> 
> This IOC is not idempotent as pages EADDed at this point can not be
> re-EADDed again. So we can't return ERESTARTSYS

Ah, and now I remember why I opted for modifying the parameters directly
instead of including a "number processed" field.  Andy pointed out the
ERESTARTSYS thing in the original multi-page add RFC[*], so presumably
updating the params and returning ERESTARTSYS is legal/acceptable.

[*] https://lkml.kernel.org/r/CALCETrUb4X9_L9RXKhmyNpfSCsbNodP=BfbfO8Fz_efq24jp8w@mail.gmail.com