x86/xen: fix init of balloon stats again

The handling of extra memory regions done in balloon_add_regions() is not
correct for PV guests, since the initial target is set to reflect the real
memory the system has, not what's described on the memory map, which can be
higher if memory != maxmem.

Introduce separate logic for addition vs subtraction in
balloon_add_regions() and handle extra regions correctly by adding them to
the total amount of pages, instead of subtracting from the current and
target pages amounts.

In the common case PV domU/dom0 and PVH dom0 will use the addition path,
since the initial target reflects the real assigned memory.  HVM and PVH
domUs use the subtraction path, since the target is set based on the amount
of memory reported in the memory map, without accounting for released
regions.

Fixes: 87af633689ce ("x86/xen: fix balloon target initialization for PVH dom0")
Fixes: 0949c646d646 ("Partial revert "x86/xen: fix balloon target initialization for PVH dom0"")
Signed-off-by: Roger Pau Monné <roger@xenproject.org>
Cc: stable@vger.kernel.org
Reviewed-by: Juergen Gross <jgross@suse.com>
Tested-by: Matthias Goergens <matthias.goergens@gmail.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20260805094008.95778-1-roger@xenproject.org>

0 files changed, 0 insertions, 0 deletions