linux-kernel - Re: [RFC PATCH v4 11/28] x86: Add support to determine the E820 type of an address

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Date:   Mon, 20 Feb 2017 21:09:55 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Larry Woodman <lwoodman@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v4 11/28] x86: Add support to determine the E820 type
 of an address

On Thu, Feb 16, 2017 at 09:44:30AM -0600, Tom Lendacky wrote:
> This patch adds support to return the E820 type associated with an address

s/This patch adds/Add/

> range.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/include/asm/e820/api.h   |    2 ++
>  arch/x86/include/asm/e820/types.h |    2 ++
>  arch/x86/kernel/e820.c            |   26 +++++++++++++++++++++++---
>  3 files changed, 27 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/e820/api.h b/arch/x86/include/asm/e820/api.h
> index 8e0f8b8..7c1bdc9 100644
> --- a/arch/x86/include/asm/e820/api.h
> +++ b/arch/x86/include/asm/e820/api.h
> @@ -38,6 +38,8 @@
>  extern void e820__reallocate_tables(void);
>  extern void e820__register_nosave_regions(unsigned long limit_pfn);
>  
> +extern enum e820_type e820__get_entry_type(u64 start, u64 end);
> +
>  /*
>   * Returns true iff the specified range [start,end) is completely contained inside
>   * the ISA region.
> diff --git a/arch/x86/include/asm/e820/types.h b/arch/x86/include/asm/e820/types.h
> index 4adeed0..bf49591 100644
> --- a/arch/x86/include/asm/e820/types.h
> +++ b/arch/x86/include/asm/e820/types.h
> @@ -7,6 +7,8 @@
>   * These are the E820 types known to the kernel:
>   */
>  enum e820_type {
> +	E820_TYPE_INVALID	= 0,
> +

Now this is strange - ACPI spec doesn't explicitly say that range type 0
is invalid. Am I looking at the wrong place?

"Table 15-312 Address Range Types12" in ACPI spec 6.

If 0 is really the invalid entry, then e820_print_type() needs updating
too. And then the invalid-entry-add should be a separate patch.

>  	E820_TYPE_RAM		= 1,
>  	E820_TYPE_RESERVED	= 2,
>  	E820_TYPE_ACPI		= 3,

-- 
Regards/Gruss,
    Boris.

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