On Tue, Nov 8, 2022 at 9:04 PM HORIGUCHI NAOYA(堀口 直也) <naoya.horiguchi@xxxxxxx> wrote: > > On Tue, Nov 08, 2022 at 04:17:06PM +0000, Luck, Tony wrote: > > > If it is feasible in future that hardware vendors can make patrol > > > scrubber programmable, we can even direct the scanning to patrol > > > scrubber. > > > > There was an attempt to create an ACPI interface for this. I don't know if it made > > it into the standard. > > I briefly checked the latest ACPI spec, and it seems that some interfaces > to control (h/w based) patrol scrubbing are defined. > > https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#acpi-ras-feature-table-rasf Thanks for the link! Once the "how to scan" part reaches consensus, we will make sure the concrete API/implementation is compatible/able to direct scan to patrol scrubber. > > > I didn't do anything with it for Linux because the interface was > > quite complex. > > > > From a h/w perspective it might always be complex. Consecutive system physical > > addresses are generally interleaved across multiple memory controllers, channels, > > DIMMs and ranks. While patrol scrubbing may be done by each memory controller > > at the channel level. > > > > So a simple request to scan a few megabytes of system physical address would > > require address translation to figure out the channel addresses on each of the > > memory controllers and programming each to scan the pieces they contribute to > > the target range. > > I expect that the physical address visible to the kernel is transparently > translated to the real address in which DIMM in which channel. > > - Naoya Horiguchi
