Re: [Xen-devel] [PATCH] xen: switch to post-init routines in xen mmu.c earlier

From: David Vrabel
Date: Wed Dec 10 2014 - 13:07:15 EST


On 10/12/14 15:56, Juergen Gross wrote:
> With the virtual mapped linear p2m list the post-init mmu operations
> must be used for setting up the p2m mappings, as in case of
> CONFIG_FLATMEM the init routines may trigger BUGs.
>
> Reported-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
> arch/x86/xen/mmu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index 6ab6150..a1a429a 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -1225,6 +1225,7 @@ static void __init xen_pagetable_p2m_setup(void)
> static void __init xen_pagetable_init(void)
> {
> paging_init();
> + xen_post_allocator_init();
>
> xen_pagetable_p2m_setup();
>

This feels very chicken-and-egg to me: To setup the P2M we need to use
the MMU ops that use the P2M...

Please explain very clearly why this is all safe.

> @@ -1236,7 +1237,6 @@ static void __init xen_pagetable_init(void)
> xen_remap_memory();
>
> xen_setup_shared_info();
> - xen_post_allocator_init();
> }
> static void xen_write_cr2(unsigned long cr2)
> {
>

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