[PATCH 7/7] KVM: arm64: Expose ID_AA64PFR2_EL1 to userspace and guests

[Marc Zyngier]

Everything is now in place for a guest to "enjoy" FP8 support.
Expose ID_AA64PFR2_EL1 to both userspace and guests, with the
explicit restriction of only being able to clear FPMR.

All other features (MTE* at the time of writing) are hidden
and not writable.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/sys_regs.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 8b5caad651512..e6f9e380283ea 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1722,6 +1722,15 @@ static u64 read_sanitised_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
 	return val;
 }
 
+static u64 read_sanitised_id_aa64pfr2_el1(struct kvm_vcpu *vcpu,
+					  const struct sys_reg_desc *rd)
+{
+	u64 val = read_sanitised_ftr_reg(SYS_ID_AA64PFR2_EL1);
+
+	/* We only expose FPMR */
+	return val & ID_AA64PFR2_EL1_FPMR;
+}
+
 #define ID_REG_LIMIT_FIELD_ENUM(val, reg, field, limit)			       \
 ({									       \
 	u64 __f_val = FIELD_GET(reg##_##field##_MASK, val);		       \
@@ -2381,7 +2390,12 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 		   ID_AA64PFR0_EL1_AdvSIMD |
 		   ID_AA64PFR0_EL1_FP), },
 	ID_SANITISED(ID_AA64PFR1_EL1),
-	ID_UNALLOCATED(4,2),
+	{ SYS_DESC(SYS_ID_AA64PFR2_EL1),
+	  .access	= access_id_reg,
+	  .get_user	= get_id_reg,
+	  .set_user	= set_id_reg,
+	  .reset	= read_sanitised_id_aa64pfr2_el1,
+	  .val		= ID_AA64PFR2_EL1_FPMR, },
 	ID_UNALLOCATED(4,3),
 	ID_WRITABLE(ID_AA64ZFR0_EL1, ~ID_AA64ZFR0_EL1_RES0),
 	ID_HIDDEN(ID_AA64SMFR0_EL1),
-- 
2.39.2