linux-kernel - Re: [PATCH RESEND] x86/xen: enable early use of set

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Date:   Mon, 20 Aug 2018 12:56:08 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org, x86@...nel.org
Cc:     hpa@...or.com, tglx@...utronix.de, mingo@...hat.com
Subject: Re: [PATCH RESEND] x86/xen: enable early use of set_fixmap in 32-bit
 Xen PV guest

On 08/20/2018 11:24 AM, Juergen Gross wrote:
> Commit 7b25b9cb0dad83 ("x86/xen/time: Initialize pv xen time in
> init_hypervisor_platform()") moved the mapping of the shared info area
> before pagetable_init(). This breaks booting as 32-bit PV guest as the
> use of set_fixmap isn't possible at this time on 32-bit.
>
> This can be worked around by populating the needed PMD on 32-bit
> kernel earlier.
>
> In order not to reimplement populate_extra_pte() using extend_brk()
> for allocating new page tables extend alloc_low_pages() to do that in
> case the early page table pool is not yet available.
>
> Fixes: 7b25b9cb0dad83 ("x86/xen/time: Initialize pv xen time in init_hypervisor_platform()")
> Signed-off-by: Juergen Gross <jgross@...e.com>
> Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
> ---
> Resending with corrected Fixes: tag
> Boris, please take this via the Xen tree (Thomas asked us to do so)


Sure, but we will need to rebase to the latest bits, so you will have to
explain yourself to Linus ;-)


-boris