Re: [RFC PATCH v3 04/20] x86: Handle reduction in physical address size with SME

From	Joerg Roedel <joro@8bytes.org>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH v3 04/20] x86: Handle reduction in physical address size with SME
Date	2016-11-15 13:20 +0100
Message-ID	<sDKSt-4PB-17@gated-at.bofh.it> (permalink)
References	<sBVfj-4HF-7@gated-at.bofh.it> <sDKSt-4PB-15@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, Nov 09, 2016 at 06:35:13PM -0600, Tom Lendacky wrote:
> +/*
> + * AMD Secure Memory Encryption (SME) can reduce the size of the physical
> + * address space if it is enabled, even if memory encryption is not active.
> + * Adjust x86_phys_bits if SME is enabled.
> + */
> +static void phys_bits_adjust(struct cpuinfo_x86 *c)
> +{

Better call this function amd_sme_phys_bits_adjust(). This name makes it
clear at the call-site why it is there and what it does.

> +	u32 eax, ebx, ecx, edx;
> +	u64 msr;
> +
> +	if (c->x86_vendor != X86_VENDOR_AMD)
> +		return;
> +
> +	if (c->extended_cpuid_level < 0x8000001f)
> +		return;
> +
> +	/* Check for SME feature */
> +	cpuid(0x8000001f, &eax, &ebx, &ecx, &edx);
> +	if (!(eax & 0x01))
> +		return;

Maybe add a comment here why you can't use cpu_has (yet).

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Re: [RFC PATCH v3 04/20] x86: Handle reduction in physical address  size with SME Joerg Roedel <joro@8bytes.org> - 2016-11-15 13:20 +0100
  Re: [RFC PATCH v3 04/20] x86: Handle reduction in physical address  size with SME Borislav Petkov <bp@alien8.de> - 2016-11-15 13:20 +0100
    Re: [RFC PATCH v3 04/20] x86: Handle reduction in physical address  size with SME Borislav Petkov <bp@alien8.de> - 2016-11-15 16:40 +0100
      Re: [RFC PATCH v3 04/20] x86: Handle reduction in physical address  size with SME Borislav Petkov <bp@alien8.de> - 2016-11-15 17:40 +0100
    Re: [RFC PATCH v3 04/20] x86: Handle reduction in physical address  size with SME Borislav Petkov <bp@alien8.de> - 2016-11-15 22:40 +0100

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