[PATCH v4 1/4] KVM: arm64: Enable writable for ID_AA64DFR0_EL1

[Jing Zhang]

Since number of context-aware breakpoints must be no more than number
of supported breakpoints according to Arm ARM, return an error if
userspace tries to set CTX_CMPS field to such value.

Signed-off-by: Jing Zhang <jingzhangos at google.com>
---
 arch/arm64/kvm/sys_regs.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 50d4e25f42d3..a6299c796d03 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1539,9 +1539,14 @@ static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu,
 			       const struct sys_reg_desc *rd,
 			       u64 val)
 {
-	u8 pmuver, host_pmuver;
+	u8 pmuver, host_pmuver, brps, ctx_cmps;
 	bool valid_pmu;
 
+	brps = FIELD_GET(ID_AA64DFR0_EL1_BRPs_MASK, val);
+	ctx_cmps = FIELD_GET(ID_AA64DFR0_EL1_CTX_CMPs_MASK, val);
+	if (ctx_cmps > brps)
+		return -EINVAL;
+
 	host_pmuver = kvm_arm_pmu_get_pmuver_limit();
 
 	/*
@@ -2061,7 +2066,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	  .get_user = get_id_reg,
 	  .set_user = set_id_aa64dfr0_el1,
 	  .reset = read_sanitised_id_aa64dfr0_el1,
-	  .val = ID_AA64DFR0_EL1_PMUVer_MASK, },
+	  .val = GENMASK(63, 0), },
 	ID_SANITISED(ID_AA64DFR1_EL1),
 	ID_UNALLOCATED(5,2),
 	ID_UNALLOCATED(5,3),
-- 
2.41.0.rc0.172.g3f132b7071-goog