linux-kernel - [PATCH v3 1/2] KVM: arm64: Make ID_AA64MMFR1_EL1.{HCX, TWED} writable from userspace

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Message-ID: <20250911114621.3724469-2-yangjinqian1@huawei.com>
Date: Thu, 11 Sep 2025 19:46:20 +0800
From: Jinqian Yang <yangjinqian1@...wei.com>
To: <oliver.upton@...ux.dev>, <yuzenghui@...wei.com>, <maz@...nel.org>
CC: <linux-arm-kernel@...ts.infradead.org>, <kvmarm@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <liuyonglong@...wei.com>,
	<wangzhou1@...ilicon.com>, <yangjinqian1@...wei.com>
Subject: [PATCH v3 1/2] KVM: arm64: Make ID_AA64MMFR1_EL1.{HCX, TWED} writable from userspace

Allow userspace to downgrade {HCX, TWED} in ID_AA64MMFR1_EL1. Userspace can
only change the value from high to low.

Signed-off-by: Jinqian Yang <yangjinqian1@...wei.com>
---
 arch/arm64/kvm/sys_regs.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 82ffb3b3b3cf..db49beb8804e 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -3002,8 +3002,6 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 				      ~(ID_AA64MMFR0_EL1_RES0 |
 					ID_AA64MMFR0_EL1_ASIDBITS)),
 	ID_WRITABLE(ID_AA64MMFR1_EL1, ~(ID_AA64MMFR1_EL1_RES0 |
-					ID_AA64MMFR1_EL1_HCX |
-					ID_AA64MMFR1_EL1_TWED |
 					ID_AA64MMFR1_EL1_XNX |
 					ID_AA64MMFR1_EL1_VH |
 					ID_AA64MMFR1_EL1_VMIDBits)),
-- 
2.33.0