Re: [Xen-devel] [Patch V2 2/2] xen: before ballooning hotplugged memory, set frames to invalid

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 03/20/2015 08:55 AM, Juergen Gross wrote:
> Commit 25b884a83d487fd62c3de7ac1ab5549979188482 ("x86/xen: set
> regions above the end of RAM as 1:1") introduced a regression.
>
> To be able to add memory pages which were added via memory hotplug to
> a pv domain, the pages must be "invalid" instead of "identity" in the
> p2m list before they can be added.
>
> Suggested-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
>   drivers/xen/balloon.c | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
>
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index 0b52d92..65fedb8 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -229,6 +229,19 @@ static enum bp_state reserve_additional_memory(long credit)
>         balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
>         nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
>   
> +#ifdef CONFIG_XEN_HAVE_PVMMU
> +       if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> +               unsigned long pfn, i;
> +
> +               pfn = PFN_DOWN(hotplug_start_paddr);
> +               for (i = 0; i < balloon_hotplug; i++)
> +                       if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
> +                               pr_warn("set_phys_to_machine() failed, no memory 
> added\n");
> +                               return BP_ECANCELED;
I should have asked last time --- should we restore [0..i-1] mapping 
back to identity on error here? I wonder whether leaving those frames as 
invalid (when they are expected to be 'identity') could cause problems 
in the future.
-boris

> +                       }
> +       }
> +#endif
> +
>         rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << 
> PAGE_SHIFT);
>   
>   	if (rc) {

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel