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

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Message-ID: <22961690-14d0-4695-ba93-a68d2517059e@suse.com>
Date: Tue, 20 Aug 2024 10:35:48 +0200
From: Jan Beulich <jbeulich@...e.com>
To: Juergen Gross <jgross@...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 20.08.2024 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.

Jan