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Date:   Wed, 23 Sep 2020 17:47:07 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Borislav Petkov <bp@alien8.de>
Cc:     Jethro Beekman <jethro@fortanix.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        x86@kernel.org, linux-sgx@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Haitao Huang <haitao.huang@linux.intel.com>,
        Chunyang Hui <sanqian.hcy@antfin.com>,
        Jordan Hand <jorhand@linux.microsoft.com>,
        Nathaniel McCallum <npmccallum@redhat.com>,
        Seth Moore <sethmo@google.com>,
        Darren Kenny <darren.kenny@oracle.com>,
        Suresh Siddha <suresh.b.siddha@intel.com>,
        akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com,
        asapek@google.com, cedric.xing@intel.com, chenalexchen@google.com,
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Subject: Re: [PATCH v38 14/24] x86/sgx: Add SGX_IOC_ENCLAVE_INIT
Message-ID: <20200923144707.GF5160@linux.intel.com>
References: <20200915112842.897265-1-jarkko.sakkinen@linux.intel.com>
 <20200915112842.897265-15-jarkko.sakkinen@linux.intel.com>
 <20200921173514.GI5901@zn.tnic>
 <20200921181021.GA24481@linux.intel.com>
 <20200921182753.GK5901@zn.tnic>
 <20200921191658.GA24823@linux.intel.com>
 <20200922082918.GC22660@zn.tnic>
 <a6f4d3e5-c128-fcd7-a1ca-5515a6c4c09a@fortanix.com>
 <20200922142909.GI22660@zn.tnic>
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Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
Precedence: bulk

On Tue, Sep 22, 2020 at 04:29:09PM +0200, Borislav Petkov wrote:
> On Tue, Sep 22, 2020 at 02:56:19PM +0200, Jethro Beekman wrote:
> > I don't see why you'd need to retry indefinitely. Yes the MSRs may not
> > match the cached value for “reasons”, but if after you've written
> > them once it still doesn't work, clearly either 1) an “unhelpful”
> > VMM is actively messing with the MSRs which I'd say is at best a VMM
> > bug or 2) there was an EPC reset and your enclave is now invalid
> > anyway, so no need to EINIT.
> 
> /me likes that even more.

OK, so I did not follow this particular discussion in high detail, so
as a sanity check I'll preview my changes.

I'd refine sgx_update_lepubkeyhash_msrs() to:

static void sgx_update_lepubkeyhash_msrs(u64 *lepubkeyhash)
{
	u64 *cache;
	int i;

	preempt_disable();

	cache = per_cpu(sgx_lepubkeyhash_cache, smp_processor_id());
	for (i = 0; i < 4; i++) {
		if (lepubkeyhash[i] != cache[i]) {
			wrmsrl(MSR_IA32_SGXLEPUBKEYHASH0 + i, lepubkeyhash[i]);
			cache[i] = lepubkeyhash[i];
		}
	}

	preempt_enable();
}

I'd drop sgx_einit() completely.

Finally, in sgx_encl_init() I would call sgx_update_lepubkeyhash_msrs()
directly:

/* ... */
			sgx_update_lepubkeyhash_msrs(mrsigner);

			ret = __einit(sigstruct, token, sgx_get_epc_addr(secs));
/* ... */

These staments would replace the call to sgx_einit().

Do I have the correct understanding?

/Jarkko