From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: David Vrabel <david.vrabel@citrix.com>, xen-devel@lists.xenproject.org
Cc: Juergen Gross <jgross@suse.com>, Kevin Moraga <kmoragas@riseup.net>
Subject: Re: [PATCHv3] x86/xen: avoid m2p lookup when setting early page table entries
Date: Thu, 23 Jun 2016 07:59:19 -0400 [thread overview]
Message-ID: <576BCF17.1040301@oracle.com> (raw)
In-Reply-To: <1466675466-7392-1-git-send-email-david.vrabel@citrix.com>
On 06/23/2016 05:51 AM, David Vrabel wrote:
> When page tables entries are set using xen_set_pte_init() during early
> boot there is no page fault handler that could handle a fault when
> performing an M2P lookup.
>
> In 64 bit guests (usually dom0) early_ioremap() would fault in
> xen_set_pte_init() because an M2P lookup faults because the MFN is in
> MMIO space and not mapped in the M2P. This lookup is done to see if
> the PFN in in the range used for the initial page table pages, so that
> the PTE may be set as read-only.
>
> The M2P lookup can be avoided by moving the check (and clear of RW)
> earlier when the PFN is still available.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> ---
> Cc: Kevin Moraga <kmoragas@riseup.net>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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next prev parent reply other threads:[~2016-06-23 11:59 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-23 9:51 [PATCHv3] x86/xen: avoid m2p lookup when setting early page table entries David Vrabel
2016-06-23 11:59 ` Boris Ostrovsky [this message]
2016-06-23 12:13 ` Juergen Gross
2016-06-23 13:06 ` David Vrabel
2016-06-23 13:27 ` Juergen Gross
2016-06-23 13:37 ` David Vrabel
2016-06-23 13:41 ` Juergen Gross
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