linux-kernel - Re: [PATCH v38 11/24] x86/sgx: Add SGX enclave driver

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Message-ID: <20201001173653.GG7474@linux.intel.com>
Date:   Thu, 1 Oct 2020 10:36:53 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     x86@...nel.org, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jethro Beekman <jethro@...tanix.com>,
        Haitao Huang <haitao.huang@...ux.intel.com>,
        Chunyang Hui <sanqian.hcy@...fin.com>,
        Jordan Hand <jorhand@...ux.microsoft.com>,
        Nathaniel McCallum <npmccallum@...hat.com>,
        Seth Moore <sethmo@...gle.com>,
        Darren Kenny <darren.kenny@...cle.com>,
        Suresh Siddha <suresh.b.siddha@...el.com>,
        andriy.shevchenko@...ux.intel.com, asapek@...gle.com, bp@...en8.de,
        cedric.xing@...el.com, chenalexchen@...gle.com,
        conradparker@...gle.com, cyhanish@...gle.com,
        dave.hansen@...el.com, haitao.huang@...el.com,
        josh@...htriplett.org, kai.huang@...el.com, kai.svahn@...el.com,
        kmoy@...gle.com, ludloff@...gle.com, luto@...nel.org,
        nhorman@...hat.com, puiterwijk@...hat.com, rientjes@...gle.com,
        tglx@...utronix.de, yaozhangx@...gle.com
Subject: Re: [PATCH v38 11/24] x86/sgx: Add SGX enclave driver

On Tue, Sep 15, 2020 at 02:28:29PM +0300, Jarkko Sakkinen wrote:
> +int __init sgx_drv_init(void)
> +{
> +	unsigned int eax, ebx, ecx, edx;
> +	u64 attr_mask, xfrm_mask;
> +	int ret;
> +	int i;
> +
> +	if (!boot_cpu_has(X86_FEATURE_SGX_LC)) {
> +		pr_info("The public key MSRs are not writable.\n");
> +		return -ENODEV;
> +	}
> +
> +	cpuid_count(SGX_CPUID, 0, &eax, &ebx, &ecx, &edx);
> +	sgx_misc_reserved_mask = ~ebx | SGX_MISC_RESERVED_MASK;
> +	sgx_encl_size_max_64 = 1ULL << ((edx >> 8) & 0xFF);
> +	sgx_encl_size_max_32 = 1ULL << (edx & 0xFF);
> +
> +	cpuid_count(SGX_CPUID, 1, &eax, &ebx, &ecx, &edx);
> +
> +	attr_mask = (((u64)ebx) << 32) + (u64)eax;
> +	sgx_attributes_reserved_mask = ~attr_mask | SGX_ATTR_RESERVED_MASK;
> +
> +	if (boot_cpu_has(X86_FEATURE_OSXSAVE)) {
> +		xfrm_mask = (((u64)edx) << 32) + (u64)ecx;
> +
> +		for (i = 2; i < 64; i++) {
> +			cpuid_count(0x0D, i, &eax, &ebx, &ecx, &edx);
> +			if ((1UL << i) & xfrm_mask)

Any reason not to use BIT()?  The max size computations are arguably not
bit operation, but XFRM is a set of bits.

> +				sgx_xsave_size_tbl[i] = eax + ebx;
> +		}
> +
> +		sgx_xfrm_reserved_mask = ~xfrm_mask;
> +	}
> +
> +	ret = misc_register(&sgx_dev_enclave);
> +	if (ret) {
> +		pr_err("Creating /dev/sgx/enclave failed with %d.\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}