linux-kernel - Re: [PATCH v2 2/7] xen: introduce generic helper checking for memory map conflicts

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Message-ID: <8d7fd92b-b71d-47fa-8684-46711f7cec31@suse.com>
Date: Thu, 22 Aug 2024 13:29:40 +0200
From: Jürgen Groß <jgross@...e.com>
To: Jan Beulich <jbeulich@...e.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, xen-devel@...ts.xenproject.org,
 Marek Marczykowski-Górecki
 <marmarek@...isiblethingslab.com>, linux-kernel@...r.kernel.org,
 x86@...nel.org
Subject: Re: [PATCH v2 2/7] xen: introduce generic helper checking for memory
 map conflicts

On 20.08.24 10:35, Jan Beulich wrote:
> On 20.08.2024 10:20, Juergen Gross wrote:
>> When booting as a Xen PV dom0 the memory layout of the dom0 is
>> modified to match that of the host, as this requires less changes in
>> the kernel for supporting Xen.
>>
>> There are some cases, though, which are problematic, as it is the Xen
>> hypervisor selecting the kernel's load address plus some other data,
>> which might conflict with the host's memory map.
>>
>> These conflicts are detected at boot time and result in a boot error.
>> In order to support handling at least some of these conflicts in
>> future, introduce a generic helper function which will later gain the
>> ability to adapt the memory layout when possible.
>>
>> Add the missing check for the xen_start_info area.
>>
>> Signed-off-by: Juergen Gross <jgross@...e.com>
>> Tested-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
> 
> Reviewed-by: Jan Beulich <jbeulich@...e.com>
> 
> However, since you mention the start_info area it may be worth adding half
> a sentence to the description also mentioning why the hypervisor allocated
> stack page doesn't need checking. In fact this may want to extend to
> initrd and phys-mach map as well, to cover everything Xen sets up on behalf
> of the kernel.

Okay.

Juergen

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