linux-kernel - Re: [PATCH v28 06/22] x86/sgx: Add wrappers for ENCLS leaf functions

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Date:   Mon, 9 Mar 2020 14:14:25 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org, akpm@...ux-foundation.org,
        dave.hansen@...el.com, nhorman@...hat.com, npmccallum@...hat.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
Subject: Re: [PATCH v28 06/22] x86/sgx: Add wrappers for ENCLS leaf functions

On Wed, Mar 04, 2020 at 01:35:53AM +0200, Jarkko Sakkinen wrote:
> +/* Issue a WARN() about an ENCLS leaf. */
> +#define ENCLS_WARN(r, name) {						  \
> +	do {								  \
> +		int _r = (r);						  \
> +		WARN(_r, "%s returned %d (0x%x)\n", (name), _r, _r); \

This should be a WARN_ONCE(), otherwise we'll spam the log if something
goes awry, e.g. if there's a correctable #MC or a rogue write to a MCi_CTL
MSR, either of which will "soft" disable SGX (CPUID 0x7 still reports
SGX/SGXLC support, but all CPUID 0x12 sub-leafs return zeros).

> +	} while (0);							  \
> +}