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Re: [PATCH V3 (resend) 01/19] x86: Create per-domain mapping of guest_root_pt


  • To: Elias El Yandouzi <eliasely@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 14 May 2024 16:51:08 +0200
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  • Cc: julien@xxxxxxx, pdurrant@xxxxxxxxxx, dwmw@xxxxxxxxxx, Hongyan Xia <hongyxia@xxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Julien Grall <jgrall@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Tue, 14 May 2024 14:51:12 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 13.05.2024 15:40, Elias El Yandouzi wrote:
> From: Hongyan Xia <hongyxia@xxxxxxxxxx>
> 
> Create a per-domain mapping of PV guest_root_pt as direct map is being
> removed.
> 
> Note that we do not map and unmap root_pgt for now since it is still a
> xenheap page.
> 
> Signed-off-by: Hongyan Xia <hongyxia@xxxxxxxxxx>
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
> Signed-off-by: Elias El Yandouzi <eliasely@xxxxxxxxxx>
> 
> ----
>     Changes in V3:
>         * Rename SHADOW_ROOT
>         * Haven't addressed the potentially over-allocation issue as I don't 
> get it

I thought I had explained in enough detail that the GDT/LDT area needs
quite a bit more space (2 times 64k per vCPU) than the root PT one (4k
per vCPU). Thus while d->arch.pv.gdt_ldt_l1tab really needs to point at
a full page (as long as not taking into account dynamic domain
properties), d->arch.pv.root_pt_l1tab doesn't need to (and hence might
better be allocated using xzalloc() / xzalloc_array(), even when also
not taking into account dynamic domain properties, i.e. vCPU count).

Jan



 


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