linux-kernel - Re: [tip:x86/urgent] x86, cpu, amd: Add workaround for family 16h, erratum 793

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Message-ID: <52D5DC51.9010606@zytor.com>
Date:	Tue, 14 Jan 2014 16:54:41 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	mingo@...nel.org, linux-kernel@...r.kernel.org,
	aravind.gopalakrishnan@....com, tglx@...utronix.de, bp@...e.de,
	hpa@...ux.intel.com, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86, cpu, amd: Add workaround for family 16h,
 erratum 793

On 01/14/2014 04:45 PM, tip-bot for Borislav Petkov wrote:
> +		rdmsrl(MSR_AMD64_LS_CFG, val);
> +		if (!(val & BIT(15)))
> +			wrmsrl(MSR_AMD64_LS_CFG, val | BIT(15));

Incidentally, I'm wondering if we shouldn't have a
set_in_msr()/clear_in_msr() set of functions which would incorporate the
above construct:

void set_in_msr(u32 msr, u64 mask)
{
	u64 old, new;

	old = rdmsrl(msr);
	new = old | mask;
	if (old != new)
		wrmsrl(msr, new);
}

... and the obvious equivalent for clear_in_msr().

The perhaps only question is if it should be "set/clear_bit_in_msr()"
rather than having to haul a full 64-bit mask in the common case.

	-hpa


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