From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <ian.campbell@citrix.com>
Subject: Re: [PATCH v4] xen/arm: Add RESERVE option to reserve
 non-leaf level table entries
Date: Tue, 24 Mar 2015 16:53:58 +0000
Message-ID: <1427216038.21742.457.camel@citrix.com>
References: <1427197487-8216-1-git-send-email-vijay.kilari@gmail.com>
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To: vijay.kilari@gmail.com
Cc: stefano.stabellini@eu.citrix.com, Prasun.Kapoor@caviumnetworks.com, vijaya.kumar@caviumnetworks.com, julien.grall@linaro.org, tim@xen.org, xen-devel@lists.xen.org, stefano.stabellini@citrix.com, jbeulich@suse.com, manish.jaggi@caviumnetworks.com
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On Tue, 2015-03-24 at 17:14 +0530, vijay.kilari@gmail.com wrote:
> From: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
> 
> On x86, for the pages mapped with PAGE_HYPERVISOR attribute
> non-leaf page tables are allocated with valid pte entries.
> and with MAP_SMALL_PAGES attribute only non-leaf page tables are
> allocated with invalid (valid bit set to 0) pte entries.
> However on arm this is not the case. On arm for the pages
> mapped with PAGE_HYPERVISOR and MAP_SMALL_PAGES both
> non-leaf and leaf level page table are allocated with valid bit
> in pte entries.
> 
> This behaviour in arm makes common vmap code fail to
> allocate memory beyond 128MB as described below.
> 
> In vm_init, map_pages_to_xen() is called for mapping
> vm_bitmap. Initially one page of vm_bitmap is allocated
> and mapped using PAGE_HYPERVISOR attribute.
> For the rest of vm_bitmap pages, MAP_SMALL_PAGES attribute
> is used to map.
> 
> In ARM for both PAGE_HYPERVISOR and MAP_SMALL_PAGES, valid bit
> is set to 1 in pte entry for these mapping.
> 
> In vm_alloc(), map_pages_to_xen() is failing for >128MB because
> for this next vm_bitmap page the mapping is already set in vm_init()
> with valid bit set in pte entry. So map_pages_to_xen() in
> ARM returns error.
> 
> With this patch, MAP_SMALL_PAGES is dropped and arch specific
> populate_pt_range() api is introduced to populate non-leaf
> page table entries for the requested pages. Added RESERVE option
> to map non-leaf page table entries.
> 
> Signed-off-by: Vijaya Kumar K<Vijaya.Kumar@caviumnetworks.com>
> Acked-by: Jan Beulich <jbeulich@suse.com>

Acked + applied, thanks.

I changed the title to the more complete/correct: "xen: Add
populate_pt_range interface to reserve non-leaf level table entries". I
hope that is OK.

Ian.