[PATCH v15 31/37] KVM: arm64: CCA: Propagate breakpoint and watchpoint counts to userspace

From: Jean-Philippe Brucker <[email protected]>

The RMM describes the maximum number of BPs/WPs available to the guest
in the Feature Register 0. Propagate those numbers into ID_AA64DFR0_EL1,
which is visible to userspace. A VMM needs this information in order to
set up realm parameters.

Signed-off-by: Jean-Philippe Brucker <[email protected]>
Signed-off-by: Steven Price <[email protected]>
Reviewed-by: Gavin Shan <[email protected]>
Reviewed-by: Suzuki K Poulose <[email protected]>
Reviewed-by: Joey Gouly <[email protected]>
---
 arch/arm64/include/asm/kvm_rmi.h |  2 ++
 arch/arm64/kvm/rmi.c             | 19 +++++++++++++++++++
 arch/arm64/kvm/sys_regs.c        |  3 +++
 3 files changed, 24 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
index 7f0c059ac7cf..3ec6525ae95f 100644
--- a/arch/arm64/include/asm/kvm_rmi.h
+++ b/arch/arm64/include/asm/kvm_rmi.h
@@ -96,6 +96,8 @@ struct realm_rec {
 void kvm_init_rmi(void);
 u32 kvm_rmm_ipa_limit(void);
 
+u64 kvm_realm_reset_id_aa64dfr0_el1(const struct kvm_vcpu *vcpu, u64 val);
+
 bool kvm_rmi_supports_sve(void);
 
 int kvm_init_realm(struct kvm *kvm);
diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
index 2310f2b608a7..491097a57328 100644
--- a/arch/arm64/kvm/rmi.c
+++ b/arch/arm64/kvm/rmi.c
@@ -35,6 +35,25 @@ u32 kvm_rmm_ipa_limit(void)
 	return u64_get_bits(rmi_feat_reg(0), RMI_FEATURE_REGISTER_0_S2SZ);
 }
 
+u64 kvm_realm_reset_id_aa64dfr0_el1(const struct kvm_vcpu *vcpu, u64 val)
+{
+	u32 bps = u64_get_bits(rmi_feat_reg(0), RMI_FEATURE_REGISTER_0_NUM_BPS);
+	u32 wps = u64_get_bits(rmi_feat_reg(0), RMI_FEATURE_REGISTER_0_NUM_WPS);
+	u32 ctx_cmps;
+
+	/* Ensure CTX_CMPs is still valid */
+	ctx_cmps = FIELD_GET(ID_AA64DFR0_EL1_CTX_CMPs, val);
+	ctx_cmps = min(bps, ctx_cmps);
+
+	val &= ~(ID_AA64DFR0_EL1_BRPs_MASK | ID_AA64DFR0_EL1_WRPs_MASK |
+		 ID_AA64DFR0_EL1_CTX_CMPs);
+	val |= FIELD_PREP(ID_AA64DFR0_EL1_BRPs_MASK, bps) |
+	       FIELD_PREP(ID_AA64DFR0_EL1_WRPs_MASK, wps) |
+	       FIELD_PREP(ID_AA64DFR0_EL1_CTX_CMPs, ctx_cmps);
+
+	return val;
+}
+
 static int get_start_level(struct realm *realm)
 {
 	return 4 - stage2_pgtable_levels(realm->ia_bits);
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 5d5c579d4579..e0fe9f2562bc 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -2142,6 +2142,9 @@ static u64 sanitise_id_aa64dfr0_el1(const struct kvm_vcpu *vcpu, u64 val)
 	/* Hide BRBE from guests */
 	val &= ~ID_AA64DFR0_EL1_BRBE_MASK;
 
+	if (vcpu_is_rec(vcpu))
+		return kvm_realm_reset_id_aa64dfr0_el1(vcpu, val);
+
 	return val;
 }
 
-- 
2.43.0