linux-kernel - Re: [RFC PATCH v2 1/2] xen/pvh: Add memory map pointer to hvm_start

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Message-ID: <94195d5b-fb04-0e27-4fd5-ab3c13b58d07@redhat.com>
Date:   Mon, 11 Dec 2017 22:59:47 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jan Beulich <JBeulich@...e.com>,
        Maran Wilson <maran.wilson@...cle.com>
Cc:     andrew.cooper3@...rix.com, roger.pau@...rix.com, hch@...radead.org,
        x86@...nel.org, tglx@...utronix.de, xen-devel@...ts.xenproject.org,
        boris.ostrovsky@...cle.com, mingo@...hat.com, rkrcmar@...hat.com,
        Juergen Gross <jgross@...e.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, hpa@...or.com
Subject: Re: [RFC PATCH v2 1/2] xen/pvh: Add memory map pointer to
 hvm_start_info struct

On 08/12/2017 09:49, Jan Beulich wrote:
>> + * The layout of each entry in the memory map table is as follows and no
>> + * padding is used between entries in the array:
>> + *
>> + *  0 +----------------+
>> + *    | addr           | Base address
>> + *  8 +----------------+
>> + *    | size           | Size of mapping
>> + * 16 +----------------+
>> + *    | type           | E820_TYPE_xxx
>> + * 20 +----------------|
> I'm not convinced of re-using E820 types here. I can see that this
> might ease the consumption in Linux, but I don't think there should
> be any connection to x86 aspects here - the data being supplied is
> x86-agnostic, and Linux'es placement of the header is also making
> no connection to x86 (oddly enough, the current placement in the
> Xen tree does, for a reason which escapes me).

FWIW, e820 types are now part of the ACPI standard.  So using them is
not necessarily related to x86, and reasonably x86-agnostic.

Paolo

> I could also imagine reasons to add new types without them being
> sanctioned by whoever maintains E820 type assignments.