Re: [PATCH] x86: Don't crash when mapping a page using EFI runtime page tables

["Jan Beulich" <JBeulich@suse.com>]

>>> On 15.05.15 at 18:08, <ross.lagerwall@citrix.com> wrote:
> --- a/xen/arch/x86/domain_page.c
> +++ b/xen/arch/x86/domain_page.c
> @@ -32,20 +32,25 @@ static inline struct vcpu *mapcache_current_vcpu(void)
>          return NULL;
>  
>      /*
> +     * When using efi runtime page tables, we have the equivalent of the idle
> +     * domain's page tables but current may point at another domain's VCPU.
> +     * Return NULL as though current is not properly set up yet.
> +     */
> +    if ( efi_enabled && read_cr3() == efi_rs_page_table() )
> +        return NULL;

While I think this is an issue even without your change, it highlights
that we need to sync updates to idle_pg_table[] into efi_l4_pgtable[]
(particularly such done during memory hotplug, but I'd envision this
to be done generically in virt_to_xen_l3e()) for this to work.

Jan