Re: [Xen-devel] [PATCH] xen: fix dom0 boot on huge systems

[Jan Beulich]

>>> On 07.03.19 at 10:11, <jgross@xxxxxxxx> wrote:
> Commit f7c90c2aa40048 ("x86/xen: don't write ptes directly in 32-bit
> PV guests") introduced a regression for booting dom0 on huge systems
> with lots of RAM (in the TB range).
> 
> Reason is that on those hosts the p2m list needs to be moved early in
> the boot process and this requires temporary page tables to be created.
> Said commit modified xen_set_pte_init() to use a hypercall for writing
> a PTE, but this requires the page table being in the direct mapped
> area, which is not the case for the temporary page tables used in
> xen_relocate_p2m().
> 
> As the page tables are completely written before being linked to the
> actual address space instead of set_pte() a plain write to memory can
> be used in xen_relocate_p2m().
> 
> Fixes: f7c90c2aa40048 ("x86/xen: don't write ptes directly in 32-bit PV guests")
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>