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KVM: arm64: Preserve host MPAM configuration when changing traps

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When KVM enables or disables MPAM traps to EL2 it clears all other bits in
MPAM2_EL2.  Notably, it clears the partition ids (PARTIDs) and performance
monitoring groups (PMGs). Avoid changing these bits in anticipation of
adding support for MPAM in the kernel. Otherwise, on a VHE system with the
host running at EL2 where MPAM2_EL2 and MPAM1_EL1 access the same register,
any attempt to use MPAM to monitor or partition resources for kernel space
would be foiled by running a KVM guest. Additionally, MPAM2_EL2.EnMPAMSM is
always set to 0 which causes MPAMSM_EL1 to always trap. Keep EnMPAMSM set
to 1 when not in a guest so that the kernel can use MPAMSM_EL1.

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>
Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
This commit is contained in:
Ben Horgan 2026-03-13 14:45:41 +00:00 committed by James Morse
parent 29fa1be82b
commit eda1cd1f9d
1 changed files with 8 additions and 4 deletions
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12
arch/arm64/kvm/hyp/include/hyp/switch.h
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@ -267,7 +267,8 @@ static inline void __deactivate_traps_hfgxtr(struct kvm_vcpu *vcpu)
static inline void __activate_traps_mpam(struct kvm_vcpu *vcpu)
{
u64 r = MPAM2_EL2_TRAPMPAM0EL1 | MPAM2_EL2_TRAPMPAM1EL1;
u64 clr = MPAM2_EL2_EnMPAMSM;
u64 set = MPAM2_EL2_TRAPMPAM0EL1 | MPAM2_EL2_TRAPMPAM1EL1;
if (!system_supports_mpam())
return;
@ -277,18 +278,21 @@ static inline void __activate_traps_mpam(struct kvm_vcpu *vcpu)
write_sysreg_s(MPAMHCR_EL2_TRAP_MPAMIDR_EL1, SYS_MPAMHCR_EL2);
} else {
/* From v1.1 TIDR can trap MPAMIDR, set it unconditionally */
r |= MPAM2_EL2_TIDR;
set |= MPAM2_EL2_TIDR;
}
write_sysreg_s(r, SYS_MPAM2_EL2);
sysreg_clear_set_s(SYS_MPAM2_EL2, clr, set);
}
static inline void __deactivate_traps_mpam(void)
{
u64 clr = MPAM2_EL2_TRAPMPAM0EL1 | MPAM2_EL2_TRAPMPAM1EL1 | MPAM2_EL2_TIDR;
u64 set = MPAM2_EL2_EnMPAMSM;
if (!system_supports_mpam())
return;
write_sysreg_s(0, SYS_MPAM2_EL2);
sysreg_clear_set_s(SYS_MPAM2_EL2, clr, set);
if (system_supports_mpam_hcr())
write_sysreg_s(MPAMHCR_HOST_FLAGS, SYS_MPAMHCR_EL2);