[RFC PATCH v3 22/29] KVM: arm64: Trap disabled features of ID_AA64PFR0_EL1

[Reiji Watanabe]

Add feature_config_ctrl for RAS and AMU, which are indicated in
ID_AA64PFR0_EL1, to program configuration registers to trap
guest's using those features when they are not exposed to the guest.

Introduce trap_ras_regs() to change a behavior of guest's access to
the registers, which is currently raz/wi, depending on the feature's
availability for the guest (and inject undefined instruction
exception when guest's RAS register access are trapped and RAS is
not exposed to the guest).  In order to keep the current visibility
of the RAS registers from userspace (always visible), a visibility
function for RAS registers is not added.

No code is added for AMU's access/visibility handler because the
current code already injects the exception for Guest's AMU register
access unconditionally because AMU is never exposed to the guest.

Signed-off-by: Reiji Watanabe <reijiw at google.com>
---
 arch/arm64/kvm/sys_regs.c | 54 +++++++++++++++++++++++++++++++++------
 1 file changed, 46 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 501de08dacb7..42db8cf18fbb 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -405,6 +405,27 @@ struct feature_config_ctrl {
 	u64	cfg_val;	/* Value that are set for the field */
 };
 
+/* For ID_AA64PFR0_EL1 */
+static struct feature_config_ctrl ftr_ctrl_ras = {
+	.ftr_reg = SYS_ID_AA64PFR0_EL1,
+	.ftr_shift = ID_AA64PFR0_RAS_SHIFT,
+	.ftr_min = ID_AA64PFR0_RAS_V1,
+	.ftr_signed = FTR_UNSIGNED,
+	.cfg_reg = VCPU_HCR_EL2,
+	.cfg_mask = (HCR_TERR | HCR_TEA | HCR_FIEN),
+	.cfg_val = (HCR_TERR | HCR_TEA),
+};
+
+static struct feature_config_ctrl ftr_ctrl_amu = {
+	.ftr_reg = SYS_ID_AA64PFR0_EL1,
+	.ftr_shift = ID_AA64PFR0_AMU_SHIFT,
+	.ftr_min = ID_AA64PFR0_AMU,
+	.ftr_signed = FTR_UNSIGNED,
+	.cfg_reg = VCPU_CPTR_EL2,
+	.cfg_mask = CPTR_EL2_TAM,
+	.cfg_val = CPTR_EL2_TAM,
+};
+
 struct id_reg_info {
 	u32	sys_reg;	/* Register ID */
 	u64	sys_val;	/* Sanitized system value */
@@ -871,6 +892,11 @@ static struct id_reg_info id_aa64pfr0_el1_info = {
 	.init = init_id_aa64pfr0_el1_info,
 	.validate = validate_id_aa64pfr0_el1,
 	.get_reset_val = get_reset_id_aa64pfr0_el1,
+	.trap_features = &(const struct feature_config_ctrl *[]) {
+		&ftr_ctrl_ras,
+		&ftr_ctrl_amu,
+		NULL,
+	},
 };
 
 static struct id_reg_info id_aa64pfr1_el1_info = {
@@ -1027,6 +1053,18 @@ static inline bool vcpu_feature_is_available(struct kvm_vcpu *vcpu,
 	return feature_avail(ctrl, val);
 }
 
+static bool trap_ras_regs(struct kvm_vcpu *vcpu,
+			  struct sys_reg_params *p,
+			  const struct sys_reg_desc *r)
+{
+	if (!vcpu_feature_is_available(vcpu, &ftr_ctrl_ras)) {
+		kvm_inject_undefined(vcpu);
+		return false;
+	}
+
+	return trap_raz_wi(vcpu, p, r);
+}
+
 /*
  * ARMv8.1 mandates at least a trivial LORegion implementation, where all the
  * RW registers are RES0 (which we can implement as RAZ/WI). On an ARMv8.0
@@ -2318,14 +2356,14 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_AFSR1_EL1), access_vm_reg, reset_unknown, AFSR1_EL1 },
 	{ SYS_DESC(SYS_ESR_EL1), access_vm_reg, reset_unknown, ESR_EL1 },
 
-	{ SYS_DESC(SYS_ERRIDR_EL1), trap_raz_wi },
-	{ SYS_DESC(SYS_ERRSELR_EL1), trap_raz_wi },
-	{ SYS_DESC(SYS_ERXFR_EL1), trap_raz_wi },
-	{ SYS_DESC(SYS_ERXCTLR_EL1), trap_raz_wi },
-	{ SYS_DESC(SYS_ERXSTATUS_EL1), trap_raz_wi },
-	{ SYS_DESC(SYS_ERXADDR_EL1), trap_raz_wi },
-	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
-	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
+	{ SYS_DESC(SYS_ERRIDR_EL1), trap_ras_regs },
+	{ SYS_DESC(SYS_ERRSELR_EL1), trap_ras_regs },
+	{ SYS_DESC(SYS_ERXFR_EL1), trap_ras_regs },
+	{ SYS_DESC(SYS_ERXCTLR_EL1), trap_ras_regs },
+	{ SYS_DESC(SYS_ERXSTATUS_EL1), trap_ras_regs },
+	{ SYS_DESC(SYS_ERXADDR_EL1), trap_ras_regs },
+	{ SYS_DESC(SYS_ERXMISC0_EL1), trap_ras_regs },
+	{ SYS_DESC(SYS_ERXMISC1_EL1), trap_ras_regs },
 
 	MTE_REG(TFSR_EL1),
 	MTE_REG(TFSRE0_EL1),
-- 
2.34.0.rc1.387.gb447b232ab-goog