On 04.04.25 15:34, Roger Pau Monne wrote:
PVH dom0 re-uses logic from PV dom0, in which RAM ranges not assigned to dom0 are re-used as scratch memory to map foreign and grant pages. Such logic relies on reporting those unpopulated ranges as RAM to Linux, and mark them as reserved. This way Linux creates the underlying page structures required for metadata management.Such approach works fine on PV because the initial balloon target is calculated using specific Xen data, that doesn't take into account the memory type changes described above. However on HVM and PVH the initial balloon target is calculated using get_num_physpages(), and that function does take into account the unpopulated RAM regions used as scratch space for remote domain mappings. This leads to PVH dom0 having an incorrect initial balloon target, which causes malfunction (excessive memory freeing) of the balloon driver if the dom0 memory target is later adjusted from the toolstack. Fix this by using xen_released_pages to account for any pages that are part of the memory map, but are already unpopulated when the balloon driver is initialized. This accounts for any regions used for scratch remote mappings. Take the opportunity to unify PV with PVH/HVM guests regarding the usage of get_num_physpages(), as that avoids having to add different logic for PV vs PVH in both balloon_add_regions() and arch_xen_unpopulated_init(). Much like a6aa4eb994ee, the code in this changeset should have been part of 38620fc4e893. Fixes: a6aa4eb994ee ('xen/x86: add extra pages to unpopulated-alloc if available') Signed-off-by: Roger Pau Monné <roger....@citrix.com>
Reviewed-by: Juergen Gross <jgr...@suse.com> Juergen
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