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| author | James Morse <james.morse@arm.com> | 2026-03-13 17:45:44 +0300 |
|---|---|---|
| committer | James Morse <james.morse@arm.com> | 2026-03-27 18:28:25 +0300 |
| commit | 87b78a5d70e83d4dbe31e1afda2be736a3330b31 (patch) | |
| tree | 7162b539430eb168f52b336f27750243a008e46b | |
| parent | 8e06d04ff1cf764066c62e5677bfb0b0c1d1fbbc (diff) | |
| download | linux-87b78a5d70e83d4dbe31e1afda2be736a3330b31.tar.xz | |
arm64: mpam: Re-initialise MPAM regs when CPU comes online
Now that the MPAM system registers are expected to have values that change,
reprogram them based on the previous value when a CPU is brought online.
Previously MPAM's 'default PARTID' of 0 was always used for MPAM in
kernel-space as this is the PARTID that hardware guarantees to
reset. Because there are a limited number of PARTID, this value is exposed
to user-space, meaning resctrl changes to the resctrl default group would
also affect kernel threads. Instead, use the task's PARTID value for
kernel work on behalf of user-space too. The default of 0 is kept for both
user-space and kernel-space when MPAM is not enabled.
Tested-by: Gavin Shan <gshan@redhat.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Zeng Heng <zengheng4@huawei.com>
Tested-by: Punit Agrawal <punit.agrawal@oss.qualcomm.com>
Tested-by: Jesse Chick <jessechick@os.amperecomputing.com>
Reviewed-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Co-developed-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
| -rw-r--r-- | arch/arm64/kernel/cpufeature.c | 19 |
1 files changed, 12 insertions, 7 deletions
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index c31f8e17732a..c3f900f81653 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -86,6 +86,7 @@ #include <asm/kvm_host.h> #include <asm/mmu.h> #include <asm/mmu_context.h> +#include <asm/mpam.h> #include <asm/mte.h> #include <asm/hypervisor.h> #include <asm/processor.h> @@ -2492,13 +2493,17 @@ test_has_mpam(const struct arm64_cpu_capabilities *entry, int scope) static void cpu_enable_mpam(const struct arm64_cpu_capabilities *entry) { - /* - * Access by the kernel (at EL1) should use the reserved PARTID - * which is configured unrestricted. This avoids priority-inversion - * where latency sensitive tasks have to wait for a task that has - * been throttled to release the lock. - */ - write_sysreg_s(0, SYS_MPAM1_EL1); + int cpu = smp_processor_id(); + u64 regval = 0; + + if (IS_ENABLED(CONFIG_ARM64_MPAM) && static_branch_likely(&mpam_enabled)) + regval = READ_ONCE(per_cpu(arm64_mpam_current, cpu)); + + write_sysreg_s(regval | MPAM1_EL1_MPAMEN, SYS_MPAM1_EL1); + isb(); + + /* Synchronising the EL0 write is left until the ERET to EL0 */ + write_sysreg_s(regval, SYS_MPAM0_EL1); } static bool |