linux-kernel - [PATCH] KVM: arm64: Check cpu_has_spe() before initializing PMSCR

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Message-ID: <20251007182356.2813920-1-mukesh.ojha@oss.qualcomm.com>
Date: Tue,  7 Oct 2025 23:53:56 +0530
From: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
To: maz@...nel.org, oliver.upton@...ux.dev, joey.gouly@....com,
        suzuki.poulose@....com, yuzenghui@...wei.com, catalin.marinas@....com,
        will@...nel.org
Cc: alexandru.elisei@....com, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Mukesh Ojha <mukesh.ojha@....qualcomm.com>
Subject: [PATCH] KVM: arm64: Check cpu_has_spe() before initializing PMSCR_EL1 in VHE

commit efad60e46057 ("KVM: arm64: Initialize PMSCR_EL1 when in VHE")
initializes PMSCR_EL1 to 0 which is making the boot up stuck when KVM
runs in VHE mode and reverting the change is fixing the issue.

[    2.967447] RPC: Registered tcp NFSv4.1 backchannel transport module.
[    2.974061] PCI: CLS 0 bytes, default 64
[    2.978171] Unpacking initramfs...
[    2.982889] kvm [1]: nv: 568 coarse grained trap handlers
[    2.988573] kvm [1]: IPA Size Limit: 40 bits

Lets guard the change with cpu_has_spe() check so that it only affects
the cpu which has SPE feature supported.

Fixes: efad60e46057 ("KVM: arm64: Initialize PMSCR_EL1 when in VHE")
Signed-off-by: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
---
 arch/arm64/kvm/debug.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index 3515a273eaa2..d9fd45f0db9a 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -15,6 +15,14 @@
 #include <asm/kvm_arm.h>
 #include <asm/kvm_emulate.h>
 
+static int cpu_has_spe(void)
+{
+	u64 dfr0 = read_sysreg(id_aa64dfr0_el1);
+
+	return cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_PMSVer_SHIFT) &&
+	       !(read_sysreg_s(SYS_PMBIDR_EL1) & PMBIDR_EL1_P);
+}
+
 /**
  * kvm_arm_setup_mdcr_el2 - configure vcpu mdcr_el2 value
  *
@@ -80,8 +88,7 @@ void kvm_init_host_debug_data(void)
 	if (has_vhe())
 		return;
 
-	if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_PMSVer_SHIFT) &&
-	    !(read_sysreg_s(SYS_PMBIDR_EL1) & PMBIDR_EL1_P))
+	if (cpu_has_spe())
 		host_data_set_flag(HAS_SPE);
 
 	/* Check if we have BRBE implemented and available at the host */
@@ -101,8 +108,8 @@ void kvm_init_host_debug_data(void)
 
 void kvm_debug_init_vhe(void)
 {
-	/* Clear PMSCR_EL1.E{0,1}SPE which reset to UNKNOWN values. */
-	if (SYS_FIELD_GET(ID_AA64DFR0_EL1, PMSVer, read_sysreg(id_aa64dfr0_el1)))
+	if (cpu_has_spe())
+		/* Clear PMSCR_EL1.E{0,1}SPE which reset to UNKNOWN values. */
 		write_sysreg_el1(0, SYS_PMSCR);
 }
 
-- 
2.50.1