kernel/linux.git/drivers/xen/balloon.c, branch v7.1

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using git grep -l '\

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

xen/balloon: improve accuracy of initial balloon target for dom0

2026-02-02T06:31:22+00:00

The dom0 balloon target set by the toolstack is the value returned by XENMEM_current_reservation. Do the same in the kernel balloon driver and set the current allocation to the value returned by XENMEM_current_reservation. On my test system this causes the kernel balloon driver target to exactly match the value set by the toolstack in xenstore. Note this approach can be used by both PV and PVH dom0s, as the toolstack always uses XENMEM_current_reservation to set the initial target regardless of the dom0 type. Signed-off-by: Roger Pau Monné Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross Message-ID: <20260128110510.46425-3-roger.pau@citrix.com>

Partial revert "x86/xen: fix balloon target initialization for PVH dom0"

2026-02-02T06:31:22+00:00

This partially reverts commit 87af633689ce16ddb166c80f32b120e50b1295de so the current memory target for PV guests is still fetched from start_info->nr_pages, which matches exactly what the toolstack sets the initial memory target to. Using get_num_physpages() is possible on PV also, but needs adjusting to take into account the ISA hole and the PFN at 0 not considered usable memory despite being populated, and hence would need extra adjustments. Instead of carrying those extra adjustments switch back to the previous code. That leaves Linux with a difference in how current memory target is obtained for HVM vs PV, but that's better than adding extra logic just for PV. However if switching to start_info->nr_pages for PV domains we need to differentiate between released pages (freed back to the hypervisor) as opposed to pages in the physmap which are not populated to start with. Introduce a new xen_unpopulated_pages to account for papges that have never been populated, and hence in the PV case don't need subtracting. Fixes: 87af633689ce ("x86/xen: fix balloon target initialization for PVH dom0") Reported-by: James Dingwall Signed-off-by: Roger Pau Monné Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross Message-ID: <20260128110510.46425-2-roger.pau@citrix.com>

xen: replace XENFEAT_auto_translated_physmap with xen_pv_domain()

2025-09-08T15:01:36+00:00

Instead of testing the XENFEAT_auto_translated_physmap feature, just use !xen_pv_domain() which is equivalent. This has the advantage that a kernel not built with CONFIG_XEN_PV will be smaller due to dead code elimination. Reviewed-by: Jason Andryuk Signed-off-by: Juergen Gross Message-ID: <20250826145608.10352-3-jgross@suse.com>

xen/x86: fix initial memory balloon target

2025-05-23T05:09:00+00:00

When adding extra memory regions as ballooned pages also adjust the balloon target, otherwise when the balloon driver is started it will populate memory to match the target value and consume all the extra memory regions added. This made the usage of the Xen `dom0_mem=,max:` command line parameter for dom0 not work as expected, as the target won't be adjusted and when the balloon is started it will populate memory straight to the 'max:' value. It would equally affect domUs that have memory != maxmem. Kernels built with CONFIG_XEN_UNPOPULATED_ALLOC are not affected, because the extra memory regions are consumed by the unpopulated allocation driver, and then balloon_add_regions() becomes a no-op. Reported-by: John Fixes: 87af633689ce ('x86/xen: fix balloon target initialization for PVH dom0') Signed-off-by: Roger Pau Monné Reviewed-by: Juergen Gross Tested-by: Marek Marczykowski-Górecki Message-ID: <20250514080427.28129-1-roger.pau@citrix.com> Signed-off-by: Juergen Gross

x86/xen: fix balloon target initialization for PVH dom0

2025-04-07T09:24:12+00:00

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. Note on x86 xen_released_pages definition is moved to enlighten.c so it's uniformly available for all Xen-enabled builds. 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 Reviewed-by: Juergen Gross Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross Message-ID: <20250407082838.65495-1-roger.pau@citrix.com>

xen: balloon: update the NR_BALLOON_PAGES state

2025-03-22T05:03:13+00:00

Update the NR_BALLOON_PAGES counter when pages are added to or removed from the Xen balloon. Link: https://lkml.kernel.org/r/20250314213757.244258-5-npache@redhat.com Signed-off-by: Nico Pache Reviewed-by: Juergen Gross Cc: Alexander Atanasov Cc: Chengming Zhou Cc: David Hildenbrand Cc: Dexuan Cui Cc: Haiyang Zhang Cc: Johannes Weiner Cc: Juegren Gross Cc: Kanchana P Sridhar Cc: K. Y. Srinivasan Cc: "Michael S. Tsirkin" Cc: Michal Hocko Cc: Muchun Song Cc: Nhat Pham Cc: Oleksandr Tyshchenko Cc: Roman Gushchin Cc: Shakeel Butt Cc: Stefano Stabellini Cc: Wei Liu Cc: Michael Kelley Signed-off-by: Andrew Morton

treewide: const qualify ctl_tables where applicable

2025-01-28T12:48:37+00:00

Add the const qualifier to all the ctl_tables in the tree except for watchdog_hardlockup_sysctl, memory_allocation_profiling_sysctls, loadpin_sysctl_table and the ones calling register_net_sysctl (./net, drivers/inifiniband dirs). These are special cases as they use a registration function with a non-const qualified ctl_table argument or modify the arrays before passing them on to the registration function. Constifying ctl_table structs will prevent the modification of proc_handler function pointers as the arrays would reside in .rodata. This is made possible after commit 78eb4ea25cd5 ("sysctl: treewide: constify the ctl_table argument of proc_handlers") constified all the proc_handlers. Created this by running an spatch followed by a sed command: Spatch: virtual patch @ depends on !(file in "net") disable optional_qualifier @ identifier table_name != { watchdog_hardlockup_sysctl, iwcm_ctl_table, ucma_ctl_table, memory_allocation_profiling_sysctls, loadpin_sysctl_table }; @@ + const struct ctl_table table_name [] = { ... }; sed: sed --in-place \ -e "s/struct ctl_table .table = &uts_kern/const struct ctl_table *table = \&uts_kern/" \ kernel/utsname_sysctl.c Reviewed-by: Song Liu Acked-by: Steven Rostedt (Google) # for kernel/trace/ Reviewed-by: Martin K. Petersen # SCSI Reviewed-by: Darrick J. Wong # xfs Acked-by: Jani Nikula Acked-by: Corey Minyard Acked-by: Wei Liu Acked-by: Thomas Gleixner Reviewed-by: Bill O'Donnell Acked-by: Baoquan He Acked-by: Ashutosh Dixit Acked-by: Anna Schumaker Signed-off-by: Joel Granados

mm/memory_hotplug: initialize memmap of !ZONE_DEVICE with PageOffline() instead of PageReserved()

2024-07-04T02:30:18+00:00

We currently initialize the memmap such that PG_reserved is set and the refcount of the page is 1. In virtio-mem code, we have to manually clear that PG_reserved flag to make memory offlining with partially hotplugged memory blocks possible: has_unmovable_pages() would otherwise bail out on such pages. We want to avoid PG_reserved where possible and move to typed pages instead. Further, we want to further enlighten memory offlining code about PG_offline: offline pages in an online memory section. One example is handling managed page count adjustments in a cleaner way during memory offlining. So let's initialize the pages with PG_offline instead of PG_reserved. generic_online_page()->__free_pages_core() will now clear that flag before handing that memory to the buddy. Note that the page refcount is still 1 and would forbid offlining of such memory except when special care is take during GOING_OFFLINE as currently only implemented by virtio-mem. With this change, we can now get non-PageReserved() pages in the XEN balloon list. From what I can tell, that can already happen via decrease_reservation(), so that should be fine. HV-balloon should not really observe a change: partial online memory blocks still cannot get surprise-offlined, because the refcount of these PageOffline() pages is 1. Update virtio-mem, HV-balloon and XEN-balloon code to be aware that hotplugged pages are now PageOffline() instead of PageReserved() before they are handed over to the buddy. We'll leave the ZONE_DEVICE case alone for now. Note that self-hosted vmemmap pages will no longer be marked as reserved. This matches ordinary vmemmap pages allocated from the buddy during memory hotplug. Now, really only vmemmap pages allocated from memblock during early boot will be marked reserved. Existing PageReserved() checks seem to be handling all relevant cases correctly even after this change. Link: https://lkml.kernel.org/r/20240607090939.89524-3-david@redhat.com Signed-off-by: David Hildenbrand Acked-by: Oscar Salvador [generic memory-hotplug bits] Cc: Alexander Potapenko Cc: Dexuan Cui Cc: Dmitry Vyukov Cc: Eugenio Pérez Cc: Haiyang Zhang Cc: Jason Wang Cc: Juergen Gross Cc: "K. Y. Srinivasan" Cc: Marco Elver Cc: Michael S. Tsirkin Cc: Mike Rapoport (IBM) Cc: Oleksandr Tyshchenko Cc: Stefano Stabellini Cc: Wei Liu Cc: Xuan Zhuo Signed-off-by: Andrew Morton