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

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Message-ID: <CAGM2rebMaogjr-EbwBOxzB8GZqGqrM-4rG-m95O6O=WwzjJ2Rw@mail.gmail.com>
Date:   Wed, 22 Aug 2018 19:28:17 +0000
From:   Pasha Tatashin <Pavel.Tatashin@...rosoft.com>
To:     "jgross@...e.com" <jgross@...e.com>
CC:     LKML <linux-kernel@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "boris.ostrovsky@...cle.com" <boris.ostrovsky@...cle.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "pasha.tatashin@...cle.com" <pasha.tatashin@...cle.com>
Subject: Re: [PATCH] x86/xen: enable early use of set_fixmap in 32-bit Xen PV
 guest

On Fri, Aug 17, 2018 at 9:41 AM Juergen Gross <jgross@...e.com> 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

Fixes: 7b25b9cb0dad ("x86/xen/time: Initialize pv xen time in
init_hypervisor_platform()")

Reviewed-by: Pavel Tatashin <pavel.tatashin@...rosoft.com>