[PATCH v4 12/41] KVM: arm64: Use kernel-space partid configuration for hypercalls

Ben Horgan
2026-02-03T21:45:10Z

On nVHE systems whether or not MPAM is enabled, EL2 continues to use
partid-0 for hypercalls, even when the host may have configured its kernel
threads to use a different partid. 0 may have been assigned to another
task. Copy the EL1 MPAM register to EL2. This ensures hypercalls use the
same partid as the kernel thread does on the host.

Tested-by: Gavin Shan <gshan@redhat.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Changes since v2:
Use mask
Use read_sysreg_el1 to cope with hvhe

Changes since v3:
Set MPAM2_EL2.MPAMEN to 1 as we rely on that before and after
---
arch/arm64/kvm/hyp/nvhe/hyp-main.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index a7c689152f68..b25a5ddb9cf0 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -635,6 +635,15 @@ static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
unsigned long hcall_min = 0;
hcall_t hfn;

+ if (system_supports_mpam()) {
+ u64 mask = MPAM1_EL1_PARTID_D | MPAM1_EL1_PARTID_I |
+ MPAM1_EL1_PMG_D | MPAM1_EL1_PMG_I;
+ u64 val = MPAM2_EL2_MPAMEN | (read_sysreg_el1(SYS_MPAM1) & mask);
+
+ write_sysreg_s(val, SYS_MPAM2_EL2);
+ isb();
+ }
+
/*
* If pKVM has been initialised then reject any calls to the
* early "privileged" hypercalls. Note that we cannot reject
--
2.43.0