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

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Message-ID: <20260203214342.584712-13-ben.horgan@arm.com>
Date: Tue,  3 Feb 2026 21:43:13 +0000
From: Ben Horgan <ben.horgan@....com>
To: ben.horgan@....com
Cc: amitsinght@...vell.com,
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	Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Subject: [PATCH v4 12/41] KVM: arm64: Use kernel-space partid configuration for hypercalls

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@...hat.com>
Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Tested-by: Peter Newman <peternewman@...gle.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>
Signed-off-by: Ben Horgan <ben.horgan@....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