Hi James, On 8/28/25 16:58, James Morse wrote: > Hi Ben, > > On 27/08/2025 09:53, Ben Horgan wrote: >> On 8/22/25 16:29, James Morse wrote: >>> The bulk of the MPAM driver lives outside the arch code because it >>> largely manages MMIO devices that generate interrupts. The driver >>> needs a Kconfig symbol to enable it, as MPAM is only found on arm64 >>> platforms, that is where the Kconfig option makes the most sense. >>> >>> This Kconfig option will later be used by the arch code to enable >>> or disable the MPAM context-switch code, and registering the CPUs >>> properties with the MPAM driver. > >>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >>> index e9bbfacc35a6..658e47fc0c5a 100644 >>> --- a/arch/arm64/Kconfig >>> +++ b/arch/arm64/Kconfig >>> @@ -2060,6 +2060,23 @@ config ARM64_TLB_RANGE >>> ARMv8.4-TLBI provides TLBI invalidation instruction that apply to a >>> range of input addresses. >>> >>> +config ARM64_MPAM >>> + bool "Enable support for MPAM" >>> + help >>> + Memory Partitioning and Monitoring is an optional extension >>> + that allows the CPUs to mark load and store transactions with >>> + labels for partition-id and performance-monitoring-group. >>> + System components, such as the caches, can use the partition-id >>> + to apply a performance policy. MPAM monitors can use the >>> + partition-id and performance-monitoring-group to measure the >>> + cache occupancy or data throughput. >>> + >>> + Use of this extension requires CPU support, support in the >>> + memory system components (MSC), and a description from firmware >>> + of where the MSC are in the address space. >>> + >>> + MPAM is exposed to user-space via the resctrl pseudo filesystem. >>> + >>> endmenu # "ARMv8.4 architectural features" > >> Should this be moved to "ARMv8.2 architectural features" rather than the >> 8.4 menu? In the arm reference manual, version L.b, I see FEAT_MPAM >> listed in the section A2.2.3.1 Features added to the Armv8.2 extension >> in later releases. > > Hmmm, I don't think we've done that anywhere else. I'm only aware of one v8.2 platform > that had it, and those are not widely available. As it was a headline v8.4 feature I'd > prefer to keep it there. > > I think its more confusing to put it under v8.2! Ok, always best to minimise confusion. Keep it in v8.4. > > Thanks, > > James -- Thanks, Ben
