Merge branch kvm-arm64/idregs-6.12 into kvmarm/fixes

* kvm-arm64/idregs-6.12:
  : .
  : Make some fields of ID_AA64DFR0_EL1 and ID_AA64PFR1_EL1
  : writable from userspace, so that a VMM can influence the
  : set of guest-visible features.
  :
  : - for ID_AA64DFR0_EL1: DoubleLock, WRPs, PMUVer and DebugVer
  :   are writable (courtesy of Shameer Kolothum)
  :
  : - for ID_AA64PFR1_EL1: BT, SSBS, CVS2_frac are writable
  :   (courtesy of Shaoqin Huang)
  : .
  KVM: selftests: aarch64: Add writable test for ID_AA64PFR1_EL1
  KVM: arm64: Allow userspace to change ID_AA64PFR1_EL1
  KVM: arm64: Use kvm_has_feat() to check if FEAT_SSBS is advertised to the guest
  KVM: arm64: Disable fields that KVM doesn't know how to handle in ID_AA64PFR1_EL1
  KVM: arm64: Make the exposed feature bits in AA64DFR0_EL1 writable from userspace

Signed-off-by: Marc Zyngier <maz@kernel.org>

2 files changed, 42 insertions, 8 deletions

diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index 5763d979d8ca..ee6573befb81 100644
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -317,7 +317,7 @@ int kvm_smccc_call_handler(struct kvm_vcpu *vcpu)
 				 * to the guest, and hide SSBS so that the
 				 * guest stays protected.
 				 */
-				if (cpus_have_final_cap(ARM64_SSBS))
+				if (kvm_has_feat(vcpu->kvm, ID_AA64PFR1_EL1, SSBS, IMP))
 					break;
 				fallthrough;
 			case SPECTRE_UNAFFECTED:
@@ -428,7 +428,7 @@ int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
  * Convert the workaround level into an easy-to-compare number, where higher
  * values mean better protection.
  */
-static int get_kernel_wa_level(u64 regid)
+static int get_kernel_wa_level(struct kvm_vcpu *vcpu, u64 regid)
 {
 	switch (regid) {
 	case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
@@ -449,7 +449,7 @@ static int get_kernel_wa_level(u64 regid)
 			 * don't have any FW mitigation if SSBS is there at
 			 * all times.
 			 */
-			if (cpus_have_final_cap(ARM64_SSBS))
+			if (kvm_has_feat(vcpu->kvm, ID_AA64PFR1_EL1, SSBS, IMP))
 				return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 			fallthrough;
 		case SPECTRE_UNAFFECTED:
@@ -486,7 +486,7 @@ int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 	case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 	case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3:
-		val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
+		val = get_kernel_wa_level(vcpu, reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
 		break;
 	case KVM_REG_ARM_STD_BMAP:
 		val = READ_ONCE(smccc_feat->std_bmap);
@@ -588,7 +588,7 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 		if (val & ~KVM_REG_FEATURE_LEVEL_MASK)
 			return -EINVAL;
 
-		if (get_kernel_wa_level(reg->id) < val)
+		if (get_kernel_wa_level(vcpu, reg->id) < val)
 			return -EINVAL;
 
 		return 0;
@@ -624,7 +624,7 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 		 * We can deal with NOT_AVAIL on NOT_REQUIRED, but not the
 		 * other way around.
 		 */
-		if (get_kernel_wa_level(reg->id) < wa_level)
+		if (get_kernel_wa_level(vcpu, reg->id) < wa_level)
 			return -EINVAL;
 
 		return 0;
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index dad88e31f953..c75dfc702a5c 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1527,6 +1527,14 @@ static u64 __kvm_read_sanitised_id_reg(const struct kvm_vcpu *vcpu,
 			val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTE);
 
 		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_SME);
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_RNDR_trap);
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_NMI);
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTE_frac);
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_GCS);
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_THE);
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTEX);
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_DF2);
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_PFAR);
 		break;
 	case SYS_ID_AA64PFR2_EL1:
 		/* We only expose FPMR */
@@ -2376,7 +2384,19 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 		   ID_AA64PFR0_EL1_RAS |
 		   ID_AA64PFR0_EL1_AdvSIMD |
 		   ID_AA64PFR0_EL1_FP), },
-	ID_SANITISED(ID_AA64PFR1_EL1),
+	ID_WRITABLE(ID_AA64PFR1_EL1, ~(ID_AA64PFR1_EL1_PFAR |
+				       ID_AA64PFR1_EL1_DF2 |
+				       ID_AA64PFR1_EL1_MTEX |
+				       ID_AA64PFR1_EL1_THE |
+				       ID_AA64PFR1_EL1_GCS |
+				       ID_AA64PFR1_EL1_MTE_frac |
+				       ID_AA64PFR1_EL1_NMI |
+				       ID_AA64PFR1_EL1_RNDR_trap |
+				       ID_AA64PFR1_EL1_SME |
+				       ID_AA64PFR1_EL1_RES0 |
+				       ID_AA64PFR1_EL1_MPAM_frac |
+				       ID_AA64PFR1_EL1_RAS_frac |
+				       ID_AA64PFR1_EL1_MTE)),
 	ID_WRITABLE(ID_AA64PFR2_EL1, ID_AA64PFR2_EL1_FPMR),
 	ID_UNALLOCATED(4,3),
 	ID_WRITABLE(ID_AA64ZFR0_EL1, ~ID_AA64ZFR0_EL1_RES0),
@@ -2390,7 +2410,21 @@ 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 |
+	/*
+	 * Prior to FEAT_Debugv8.9, the architecture defines context-aware
+	 * breakpoints (CTX_CMPs) as the highest numbered breakpoints (BRPs).
+	 * KVM does not trap + emulate the breakpoint registers, and as such
+	 * cannot support a layout that misaligns with the underlying hardware.
+	 * While it may be possible to describe a subset that aligns with
+	 * hardware, just prevent changes to BRPs and CTX_CMPs altogether for
+	 * simplicity.
+	 *
+	 * See DDI0487K.a, section D2.8.3 Breakpoint types and linking
+	 * of breakpoints for more details.
+	 */
+	  .val = ID_AA64DFR0_EL1_DoubleLock_MASK |
+		 ID_AA64DFR0_EL1_WRPs_MASK |
+		 ID_AA64DFR0_EL1_PMUVer_MASK |
 		 ID_AA64DFR0_EL1_DebugVer_MASK, },
 	ID_SANITISED(ID_AA64DFR1_EL1),
 	ID_UNALLOCATED(5,2),