[PATCH] xen/balloon: fix balloon initialization for PVH Dom0

[PATCH] xen/balloon: fix balloon initialization for PVH Dom0

[Roger Pau Monne]

The current balloon code tries to calculate a delta factor for the
balloon target when running in HVM mode in order to account for memory
used by the firmware.

This workaround for memory accounting doesn't work properly on a PVH
Dom0, that has a static-max value different from the target value even
at startup. Note that this is not a problem for DomUs because guests are
started with a static-max value that matches the amount of RAM in the
memory map.

Fix this by forcefully setting target_diff for Dom0, regardless of
it's mode.

Reported-by: Gabriel Bercarug <bercarug@amazon.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Cc: Gabriel Ercarug <bercarug@amazon.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: xen-devel@lists.xenproject.org
---
 drivers/xen/xen-balloon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/xen-balloon.c b/drivers/xen/xen-balloon.c
index b437fccd4e62..294f35ce9e46 100644
--- a/drivers/xen/xen-balloon.c
+++ b/drivers/xen/xen-balloon.c
@@ -81,7 +81,7 @@ static void watch_target(struct xenbus_watch *watch,
 			static_max = new_target;
 		else
 			static_max >>= PAGE_SHIFT - 10;
-		target_diff = xen_pv_domain() ? 0
+		target_diff = (xen_pv_domain() || xen_initial_domain()) ? 0
 				: static_max - balloon_stats.target_pages;
 	}
 
-- 
2.18.0

Re: [PATCH] xen/balloon: fix balloon initialization for PVH Dom0

[Juergen Gross]

On 08/08/18 13:46, Roger Pau Monne wrote:
> The current balloon code tries to calculate a delta factor for the
> balloon target when running in HVM mode in order to account for memory
> used by the firmware.
> 
> This workaround for memory accounting doesn't work properly on a PVH
> Dom0, that has a static-max value different from the target value even
> at startup. Note that this is not a problem for DomUs because guests are
> started with a static-max value that matches the amount of RAM in the
> memory map.
> 
> Fix this by forcefully setting target_diff for Dom0, regardless of
> it's mode.
> 
> Reported-by: Gabriel Bercarug <bercarug@amazon.com>
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

Re: [PATCH] xen/balloon: fix balloon initialization for PVH Dom0

[Boris Ostrovsky]

On 08/08/2018 07:46 AM, Roger Pau Monne wrote:
> The current balloon code tries to calculate a delta factor for the
> balloon target when running in HVM mode in order to account for memory
> used by the firmware.
>
> This workaround for memory accounting doesn't work properly on a PVH
> Dom0, that has a static-max value different from the target value even
> at startup. Note that this is not a problem for DomUs because guests are
> started with a static-max value that matches the amount of RAM in the
> memory map.
>
> Fix this by forcefully setting target_diff for Dom0, regardless of
> it's mode.
>
> Reported-by: Gabriel Bercarug <bercarug@amazon.com>
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
>


Applied to for-linus-4.19

-boris