[PATCH v3 30/32] arm64: KVM: enable initialization of a 32bit vcpu

[Marc Zyngier]

Wire the init of a 32bit vcpu by allowing 32bit modes in pstate,
and providing sensible defaults out of reset state.

This feature is of course conditioned by the presence of 32bit
capability on the physical CPU, and is checked by the KVM_CAP_ARM_EL1_32BIT
capability.

Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
---
 arch/arm64/include/asm/kvm_host.h |  2 +-
 arch/arm64/include/uapi/asm/kvm.h |  1 +
 arch/arm64/kvm/guest.c            |  6 ++++++
 arch/arm64/kvm/reset.c            | 25 ++++++++++++++++++++++++-
 include/uapi/linux/kvm.h          |  1 +
 5 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index d44064d..c3ec107 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -34,7 +34,7 @@
 #include <asm/kvm_vgic.h>
 #include <asm/kvm_arch_timer.h>
 
-#define KVM_VCPU_MAX_FEATURES 1
+#define KVM_VCPU_MAX_FEATURES 2
 
 /* We don't currently support large pages. */
 #define KVM_HPAGE_GFN_SHIFT(x)	0
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 5b1110c..5031f42 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -75,6 +75,7 @@ struct kvm_regs {
 #define KVM_VGIC_V2_CPU_SIZE		0x2000
 
 #define KVM_ARM_VCPU_POWER_OFF		0 /* CPU is started in OFF state */
+#define KVM_ARM_VCPU_EL1_32BIT		1 /* CPU running a 32bit VM */
 
 struct kvm_vcpu_init {
 	__u32 target;
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 47d3729..74ef7d5 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -93,6 +93,12 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	if (off == KVM_REG_ARM_CORE_REG(regs.pstate)) {
 		unsigned long mode = (*(unsigned long *)valp) & COMPAT_PSR_MODE_MASK;
 		switch (mode) {
+		case COMPAT_PSR_MODE_USR:
+		case COMPAT_PSR_MODE_FIQ:
+		case COMPAT_PSR_MODE_IRQ:
+		case COMPAT_PSR_MODE_SVC:
+		case COMPAT_PSR_MODE_ABT:
+		case COMPAT_PSR_MODE_UND:
 		case PSR_MODE_EL0t:
 		case PSR_MODE_EL1t:
 		case PSR_MODE_EL1h:
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index bc33e76..a282d35 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -35,11 +35,27 @@ static struct kvm_regs default_regs_reset = {
 	.regs.pstate = PSR_MODE_EL1h | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT,
 };
 
+static struct kvm_regs default_regs_reset32 = {
+	.regs.pstate = (COMPAT_PSR_MODE_SVC | COMPAT_PSR_A_BIT |
+			COMPAT_PSR_I_BIT | COMPAT_PSR_F_BIT),
+};
+
+static bool cpu_has_32bit_el1(void)
+{
+	u64 pfr0;
+
+	pfr0 = read_cpuid(ID_AA64PFR0_EL1);
+	return !!(pfr0 & 0x20);
+}
+
 int kvm_arch_dev_ioctl_check_extention(long ext)
 {
 	int r;
 
 	switch (ext) {
+	case KVM_CAP_ARM_EL1_32BIT:
+		r = cpu_has_32bit_el1();
+		break;
 	default:
 		r = 0;
 	}
@@ -62,7 +78,14 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 
 	switch (vcpu->arch.target) {
 	default:
-		cpu_reset = &default_regs_reset;
+		if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) {
+			if (!cpu_has_32bit_el1())
+				return -EINVAL;
+			cpu_reset = &default_regs_reset32;
+			vcpu->arch.hcr_el2 &= ~HCR_RW;
+		} else {
+			cpu_reset = &default_regs_reset;
+		}
 		break;
 	}
 
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 2bf42b0..ce05763 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -665,6 +665,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_PPC_EPR 86
 #define KVM_CAP_ARM_PSCI 87
 #define KVM_CAP_ARM_SET_DEVICE_ADDR 88
+#define KVM_CAP_ARM_EL1_32BIT 89
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
1.8.1.4