Commit 67faed4c authored Mar 13, 2026 by James Morse

KVM: arm64: Force guest EL1 to use user-space's partid configuration



While we trap the guest's attempts to read/write the MPAM control
registers, the hardware continues to use them. Guest-EL0 uses KVM's
user-space's configuration, as the value is left in the register, and
guest-EL1 uses either the host kernel's configuration, or in the case of
VHE, the UNKNOWN reset value of MPAM1_EL1.

We want to force the guest-EL1 to use KVM's user-space's MPAM
configuration. On nVHE rely on MPAM0_EL1 and MPAM1_EL1 always being
programmed the same and on VHE copy MPAM0_EL1 into the guest's
MPAM1_EL1. There is no need to restore as this is out of context once TGE
is set.

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>
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>

parent 2cf9ca3f

arch/arm64/kvm/hyp/vhe/sysreg-sr.c

+16 −0

Original line number	Diff line number	Diff line
		@@ -183,6 +183,21 @@ void sysreg_restore_guest_state_vhe(struct kvm_cpu_context *ctxt)
		}
		NOKPROBE_SYMBOL(sysreg_restore_guest_state_vhe);

		/*
		* The _EL0 value was written by the host's context switch and belongs to the
		* VMM. Copy this into the guest's _EL1 register.
		*/
		static inline void __mpam_guest_load(void)
		{
		u64 mask = MPAM0_EL1_PARTID_D \| MPAM0_EL1_PARTID_I \| MPAM0_EL1_PMG_D \| MPAM0_EL1_PMG_I;

		if (system_supports_mpam()) {
		u64 val = (read_sysreg_s(SYS_MPAM0_EL1) & mask) \| MPAM1_EL1_MPAMEN;

		write_sysreg_el1(val, SYS_MPAM1);
		}
		}

		/**
		* __vcpu_load_switch_sysregs - Load guest system registers to the physical CPU
		*
		@@ -222,6 +237,7 @@ void __vcpu_load_switch_sysregs(struct kvm_vcpu *vcpu)
		*/
		__sysreg32_restore_state(vcpu);
		__sysreg_restore_user_state(guest_ctxt);
		__mpam_guest_load();

		if (unlikely(is_hyp_ctxt(vcpu))) {
		__sysreg_restore_vel2_state(vcpu);