linux-kernel - Re: [PATCH v21 16/28] x86/sgx: Add the Linux SGX Enclave Driver

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Message-ID: <3cd0a591-8f30-93c1-41c7-4c74b6c3e5d2@fortanix.com>
Date:   Wed, 7 Aug 2019 16:45:22 +0000
From:   Jethro Beekman <jethro@...tanix.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        "Ayoun, Serge" <serge.ayoun@...el.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Christopherson, Sean J" <sean.j.christopherson@...el.com>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "npmccallum@...hat.com" <npmccallum@...hat.com>,
        "Katz-zamir, Shay" <shay.katz-zamir@...el.com>,
        "Huang, Haitao" <haitao.huang@...el.com>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Svahn, Kai" <kai.svahn@...el.com>, "bp@...en8.de" <bp@...en8.de>,
        "josh@...htriplett.org" <josh@...htriplett.org>,
        "luto@...nel.org" <luto@...nel.org>,
        "Huang, Kai" <kai.huang@...el.com>,
        "rientjes@...gle.com" <rientjes@...gle.com>,
        "Xing, Cedric" <cedric.xing@...el.com>
Subject: Re: [PATCH v21 16/28] x86/sgx: Add the Linux SGX Enclave Driver

ECPM permissions are mentioned in SDM EADD instruction operation. PTE I 
don't know.

--
Jethro Beekman | Fortanix

On 2019-08-07 08:17, Jarkko Sakkinen wrote:
> On Wed, Aug 07, 2019 at 06:15:34PM +0300, Jarkko Sakkinen wrote:
>> On Mon, Jul 29, 2019 at 11:17:57AM +0000, Ayoun, Serge wrote:
>>>> +	/* TCS pages need to be RW in the PTEs, but can be 0 in the EPCM. */
>>>> +	if ((secinfo.flags & SGX_SECINFO_PAGE_TYPE_MASK) ==
>>>> SGX_SECINFO_TCS)
>>>> +		prot |= PROT_READ | PROT_WRITE;
>>>
>>> For TCS pages you add both RD and WR maximum protection bits.
>>> For the enclave to be able to run, user mode will have to change the
>>> "vma->vm_flags" from PROT_NONE to PROT_READ | PROT_WRITE (otherwise
>>> eenter fails).  This is exactly what your selftest  does.
>>
>> Recap where the TCS requirements came from? Why does it need
>> RW in PTEs and can be 0 in the EPCM? The comment should explain
>> it rather leave it as a claim IMHO.
> 
> I mean after ~3 weeks of not looking into SGX (because being
> on vacation etc.) I cannot remember details of this.
> 
> /Jarkko
> 


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