On Mon, 2020-06-29 at 18:33 +0200, Rafael J. Wysocki wrote: > From: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx> > > The ACPICA's strategy with respect to the handling of memory mappings > associated with memory operation regions is to avoid mapping the > entire region at once which may be problematic at least in principle > (for example, it may lead to conflicts with overlapping mappings > having different attributes created by drivers). It may also be > wasteful, because memory opregions on some systems take up vast > chunks of address space while the fields in those regions actually > accessed by AML are sparsely distributed. > > For this reason, a one-page "window" is mapped for a given opregion > on the first memory access through it and if that "window" does not > cover an address range accessed through that opregion subsequently, > it is unmapped and a new "window" is mapped to replace it. Next, > if the new "window" is not sufficient to acess memory through the > opregion in question in the future, it will be replaced with yet > another "window" and so on. That may lead to a suboptimal sequence > of memory mapping and unmapping operations, for example if two fields > in one opregion separated from each other by a sufficiently wide > chunk of unused address space are accessed in an alternating pattern. > > The situation may still be suboptimal if the deferred unmapping > introduced previously is supported by the OS layer. For instance, > the alternating memory access pattern mentioned above may produce > a relatively long list of mappings to release with substantial > duplication among the entries in it, which could be avoided if > acpi_ex_system_memory_space_handler() did not release the mapping > used by it previously as soon as the current access was not covered > by it. > > In order to improve that, modify acpi_ex_system_memory_space_handler() > to preserve all of the memory mappings created by it until the memory > regions associated with them go away. > > Accordingly, update acpi_ev_system_memory_region_setup() to unmap all > memory associated with memory opregions that go away. > > Reported-by: Dan Williams <dan.j.williams@xxxxxxxxx> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > --- > drivers/acpi/acpica/evrgnini.c | 14 ++++---- > drivers/acpi/acpica/exregion.c | 65 ++++++++++++++++++++++++---------- > include/acpi/actypes.h | 12 +++++-- > 3 files changed, 64 insertions(+), 27 deletions(-) > Hi Rafael, Picking up from Dan while he's out - I had these patches tested by the original reporter, and they work fine. I see you had them staged in the acpica-osl branch. Is that slated to go in during the 5.9 merge window? You can add: Tested-by: Xiang Li <xiang.z.li@xxxxxxxxx>
