kernel/linux.git/arch/um/include/shared, branch v6.19.11

um: Add initial SMP support

2025-10-27T15:41:15+00:00

Add initial symmetric multi-processing (SMP) support to UML. With this support enabled, users can tell UML to start multiple virtual processors, each represented as a separate host thread. In UML, kthreads and normal threads (when running in kernel mode) can be scheduled and executed simultaneously on different virtual processors. However, the userspace code of normal threads still runs within their respective single-threaded stubs. That is, SMP support is currently available both within the kernel and across different processes, but still remains limited within threads of the same process in userspace. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20251027001815.1666872-6-tiwei.bie@linux.dev Signed-off-by: Johannes Berg

um: Define timers on a per-CPU basis

2025-10-27T15:41:15+00:00

Define timers on a per-CPU basis to enable each CPU to have its own timer. This is a preparation for adding SMP support. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20251027001815.1666872-5-tiwei.bie@linux.dev Signed-off-by: Johannes Berg

um: Determine sleep based on need_resched()

2025-10-27T15:41:15+00:00

With SMP and NO_HZ enabled, the CPU may still need to sleep even if the timer is disarmed. Switch to deciding whether to sleep based on pending resched. Additionally, because disabling IRQs does not block SIGALRM, it is also necessary to check for any pending timer alarms. This is a preparation for adding SMP support. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20251027001815.1666872-4-tiwei.bie@linux.dev Signed-off-by: Johannes Berg

um: Turn signals_* into thread-local variables

2025-10-27T15:41:15+00:00

Turn signals_enabled, signals_pending and signals_active into thread-local variables. This enables us to control and track signals independently on each CPU thread. This is a preparation for adding SMP support. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20251027001815.1666872-3-tiwei.bie@linux.dev Signed-off-by: Johannes Berg

um: Remove file-based iomem emulation support

2025-10-27T15:37:12+00:00

The file-based iomem emulation was introduced to support writing paravirtualized drivers based on emulated iomem regions. However, the only driver that makes use of it is an example driver called mmapper, which was written over two decades ago. We now have several modern device emulation mechanisms, such as vhost-user-based virtio-uml. Remove the file-based iomem emulation support to reduce the maintenance burden. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20251027054519.1996090-5-tiwei.bie@linux.dev Signed-off-by: Johannes Berg

um: Replace UML_ROUND_UP() with PAGE_ALIGN()

2025-10-27T15:37:12+00:00

Although UML_ROUND_UP() is defined in a shared header file, it depends on the PAGE_SIZE and PAGE_MASK macros, so it can only be used in kernel code. Considering its name is not very clear and its functionality is the same as PAGE_ALIGN(), replace its usages with a direct call to PAGE_ALIGN() and remove it. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20251027054519.1996090-4-tiwei.bie@linux.dev Signed-off-by: Johannes Berg

um: Make host_task_size a local variable

2025-10-27T15:37:12+00:00

Currently, host_task_size is a global variable, but it is only used in linux_main() to compute stub_start and task_size. Make it a local variable to limit its scope to where it is actually needed. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20251027054519.1996090-2-tiwei.bie@linux.dev Signed-off-by: Johannes Berg

um: move asm-offsets generation into a single file

2025-10-27T14:07:44+00:00

There's nothing subarch dependent here, and it's odd that includes need to be done in the subarch, and then entries defined in the common file. Simplify the whole thing from three files into one. Link: https://patch.msgid.link/20251007071452.367989-4-johannes@sipsolutions.net Signed-off-by: Johannes Berg

um/hostfs: define HOSTFS_ATTR_* via asm-offsets

2025-10-27T14:07:43+00:00

The HOSTFS_ATTR_* values were meant to be standalone for communication between hostfs's kernel and user code parts. However, it's easy to forget that HOSTFS_ATTR_* should be used even on the kernel side, and that wasn't consistently done. As a result, the values need to match ATTR_* values, which is not useful to maintain by hand. Instead, generate them via asm-offsets like other constants that UML needs in user-side code that aren't otherwise available in any header files that can be included there. Signed-off-by: Johannes Berg Reviewed-by: Hongbo Li Link: https://patch.msgid.link/20251007071452.367989-3-johannes@sipsolutions.net Signed-off-by: Johannes Berg

um: Centralize stub size calculations

2025-09-10T12:23:52+00:00

Currently, the stub size is calculated in multiple places. Define a macro that performs the calculation so that the code is easier to read and maintain. Signed-off-by: Tiwei Bie Signed-off-by: Johannes Berg