[PATCH v14 39/44] arm64: RMI: Set breakpoint parameters through SET_ONE_REG

[Steven Price]

From: Jean-Philippe Brucker <jean-philippe at linaro.org>

Allow userspace to configure the number of breakpoints and watchpoints
of a Realm VM through KVM_SET_ONE_REG ID_AA64DFR0_EL1.

The KVM sys_reg handler checks the user value against the maximum value
given by RMM (arm64_check_features() gets it from the
read_sanitised_id_aa64dfr0_el1() reset handler).

Userspace discovers that it can write these fields by issuing a
KVM_ARM_GET_REG_WRITABLE_MASKS ioctl.

Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org>
Signed-off-by: Steven Price <steven.price at arm.com>
Reviewed-by: Gavin Shan <gshan at redhat.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose at arm.com>
---
 arch/arm64/kvm/guest.c    |  7 +++++++
 arch/arm64/kvm/rmi.c      |  3 +++
 arch/arm64/kvm/sys_regs.c | 17 +++++++++++------
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 447674373426..fd7233e00215 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -735,6 +735,8 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	return kvm_arm_sys_reg_get_reg(vcpu, reg);
 }
 
+#define KVM_REG_ARM_ID_AA64DFR0_EL1	ARM64_SYS_REG(3, 0, 0, 5, 0)
+
 /*
  * The RMI ABI only enables setting some GPRs and PC. The selection of GPRs
  * that are available depends on the Realm state and the reason for the last
@@ -749,6 +751,11 @@ static bool validate_realm_set_reg(struct kvm_vcpu *vcpu,
 		u64 off = core_reg_offset_from_id(reg->id);
 
 		return kvm_realm_validate_core_reg(off);
+	} else {
+		switch (reg->id) {
+		case KVM_REG_ARM_ID_AA64DFR0_EL1:
+			return true;
+		}
 	}
 
 	return false;
diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
index 64e8e50f86d6..251de0a3425c 100644
--- a/arch/arm64/kvm/rmi.c
+++ b/arch/arm64/kvm/rmi.c
@@ -469,6 +469,7 @@ static int realm_create_rd(struct kvm *kvm)
 	void *rd = NULL;
 	phys_addr_t rd_phys, params_phys;
 	size_t pgd_size = kvm_pgtable_stage2_pgd_size(kvm->arch.mmu.vtcr);
+	u64 dfr0 = kvm_read_vm_id_reg(kvm, SYS_ID_AA64DFR0_EL1);
 	int r;
 
 	realm->ia_bits = VTCR_EL2_IPA(kvm->arch.mmu.vtcr);
@@ -495,6 +496,8 @@ static int realm_create_rd(struct kvm *kvm)
 	params->rtt_level_start = get_start_level(realm);
 	params->rtt_num_start = pgd_size / PAGE_SIZE;
 	params->rtt_base = kvm->arch.mmu.pgd_phys;
+	params->num_bps = SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, dfr0);
+	params->num_wps = SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, dfr0);
 
 	if (kvm->arch.arm_pmu) {
 		params->pmu_num_ctrs = kvm->arch.nr_pmu_counters;
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 10d191f83bb0..607396f378dc 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -2177,6 +2177,9 @@ static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu,
 {
 	u8 debugver = SYS_FIELD_GET(ID_AA64DFR0_EL1, DebugVer, val);
 	u8 pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer, val);
+	u8 bps = SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, val);
+	u8 wps = SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, val);
+	u8 ctx_cmps = SYS_FIELD_GET(ID_AA64DFR0_EL1, CTX_CMPs, val);
 
 	/*
 	 * Prior to commit 3d0dba5764b9 ("KVM: arm64: PMU: Move the
@@ -2196,10 +2199,11 @@ static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu,
 		val &= ~ID_AA64DFR0_EL1_PMUVer_MASK;
 
 	/*
-	 * ID_AA64DFR0_EL1.DebugVer is one of those awkward fields with a
-	 * nonzero minimum safe value.
+	 * ID_AA64DFR0_EL1.DebugVer, BRPs and WRPs all have to be greater than
+	 * zero. CTX_CMPs is never greater than BRPs.
 	 */
-	if (debugver < ID_AA64DFR0_EL1_DebugVer_IMP)
+	if (debugver < ID_AA64DFR0_EL1_DebugVer_IMP || !bps || !wps ||
+	    ctx_cmps > bps)
 		return -EINVAL;
 
 	if (ignore_feat_doublelock(vcpu, val)) {
@@ -2432,10 +2436,11 @@ static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 	mutex_lock(&vcpu->kvm->arch.config_lock);
 
 	/*
-	 * Once the VM has started the ID registers are immutable. Reject any
-	 * write that does not match the final register value.
+	 * Once the VM has started or the Realm descriptor is created, the ID
+	 * registers are immutable. Reject any write that does not match the
+	 * final register value.
 	 */
-	if (kvm_vm_has_ran_once(vcpu->kvm)) {
+	if (kvm_vm_has_ran_once(vcpu->kvm) || kvm_realm_is_created(vcpu->kvm)) {
 		if (val != read_id_reg(vcpu, rd))
 			ret = -EBUSY;
 		else
-- 
2.43.0