Merge branch kvm-arm64/aarch32-raz-idregs into kvmarm-master/next

* kvm-arm64/aarch32-raz-idregs:
  : .
  : Rework AArch32 ID registers exposed by KVM on AArch64-only
  : systems by treating them as RAZ/WI instead as UNKOWN as
  : architected, which allows them to be trivially migrated
  : between different systems.
  :
  : Patches courtesy of Oliver Upton.
  : .
  KVM: selftests: Add test for AArch32 ID registers
  KVM: arm64: Treat 32bit ID registers as RAZ/WI on 64bit-only system
  KVM: arm64: Add a visibility bit to ignore user writes
  KVM: arm64: Spin off helper for calling visibility hook
  KVM: arm64: Drop raz parameter from read_id_reg()
  KVM: arm64: Remove internal accessor helpers for id regs
  KVM: arm64: Use visibility hook to treat ID regs as RAZ

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

Author: Marc Zyngier

arch/arm64/kvm/sys_regs.c

@@ -1063,13 +1063,12 @@ static bool access_arch_timer(struct kvm_vcpu *vcpu,
 }
 
 /* Read a sanitised cpufeature ID register by sys_reg_desc */
-static u64 read_id_reg(const struct kvm_vcpu *vcpu,
-		struct sys_reg_desc const *r, bool raz)
+static u64 read_id_reg(const struct kvm_vcpu *vcpu, struct sys_reg_desc const *r)
 {
 	u32 id = reg_to_encoding(r);
 	u64 val;
 
-	if (raz)
+	if (sysreg_visible_as_raz(vcpu, r))
 		return 0;
 
 	val = read_sanitised_ftr_reg(id);
@@ -1145,34 +1144,37 @@ static unsigned int id_visibility(const struct kvm_vcpu *vcpu,
 	return 0;
 }
 
-/* cpufeature ID register access trap handlers */
-
-static bool __access_id_reg(struct kvm_vcpu *vcpu,
-			    struct sys_reg_params *p,
-			    const struct sys_reg_desc *r,
-			    bool raz)
+static unsigned int aa32_id_visibility(const struct kvm_vcpu *vcpu,
+				       const struct sys_reg_desc *r)
 {
-	if (p->is_write)
-		return write_to_read_only(vcpu, p, r);
+	/*
+	 * AArch32 ID registers are UNKNOWN if AArch32 isn't implemented at any
+	 * EL. Promote to RAZ/WI in order to guarantee consistency between
+	 * systems.
+	 */
+	if (!kvm_supports_32bit_el0())
+		return REG_RAZ | REG_USER_WI;
 
-	p->regval = read_id_reg(vcpu, r, raz);
-	return true;
+	return id_visibility(vcpu, r);
 }
 
+static unsigned int raz_visibility(const struct kvm_vcpu *vcpu,
+				   const struct sys_reg_desc *r)
+{
+	return REG_RAZ;
+}
+
+/* cpufeature ID register access trap handlers */
+
 static bool access_id_reg(struct kvm_vcpu *vcpu,
 			  struct sys_reg_params *p,
 			  const struct sys_reg_desc *r)
 {
-	bool raz = sysreg_visible_as_raz(vcpu, r);
-
-	return __access_id_reg(vcpu, p, r, raz);
-}
+	if (p->is_write)
+		return write_to_read_only(vcpu, p, r);
 
-static bool access_raz_id_reg(struct kvm_vcpu *vcpu,
-			      struct sys_reg_params *p,
-			      const struct sys_reg_desc *r)
-{
-	return __access_id_reg(vcpu, p, r, true);
+	p->regval = read_id_reg(vcpu, r);
+	return true;
 }
 
 /* Visibility overrides for SVE-specific control registers */
@@ -1208,7 +1210,7 @@ static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
 		return -EINVAL;
 
 	/* We can only differ with CSV[23], and anything else is an error */
-	val ^= read_id_reg(vcpu, rd, false);
+	val ^= read_id_reg(vcpu, rd);
 	val &= ~((0xFUL << ID_AA64PFR0_CSV2_SHIFT) |
 		 (0xFUL << ID_AA64PFR0_CSV3_SHIFT));
 	if (val)
@@ -1227,45 +1229,21 @@ static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
  * are stored, and for set_id_reg() we don't allow the effective value
  * to be changed.
  */
-static int __get_id_reg(const struct kvm_vcpu *vcpu,
-			const struct sys_reg_desc *rd, u64 *val,
-			bool raz)
-{
-	*val = read_id_reg(vcpu, rd, raz);
-	return 0;
-}
-
-static int __set_id_reg(const struct kvm_vcpu *vcpu,
-			const struct sys_reg_desc *rd, u64 val,
-			bool raz)
-{
-	/* This is what we mean by invariant: you can't change it. */
-	if (val != read_id_reg(vcpu, rd, raz))
-		return -EINVAL;
-
-	return 0;
-}
-
 static int get_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 		      u64 *val)
 {
-	bool raz = sysreg_visible_as_raz(vcpu, rd);
-
-	return __get_id_reg(vcpu, rd, val, raz);
+	*val = read_id_reg(vcpu, rd);
+	return 0;
 }
 
 static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 		      u64 val)
 {
-	bool raz = sysreg_visible_as_raz(vcpu, rd);
-
-	return __set_id_reg(vcpu, rd, val, raz);
-}
+	/* This is what we mean by invariant: you can't change it. */
+	if (val != read_id_reg(vcpu, rd))
+		return -EINVAL;
 
-static int set_raz_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
-			  u64 val)
-{
-	return __set_id_reg(vcpu, rd, val, true);
+	return 0;
 }
 
 static int get_raz_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
@@ -1367,16 +1345,26 @@ static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
 	.visibility = id_visibility,		\
 }
 
+/* sys_reg_desc initialiser for known cpufeature ID registers */
+#define AA32_ID_SANITISED(name) {		\
+	SYS_DESC(SYS_##name),			\
+	.access	= access_id_reg,		\
+	.get_user = get_id_reg,			\
+	.set_user = set_id_reg,			\
+	.visibility = aa32_id_visibility,	\
+}
+
 /*
  * sys_reg_desc initialiser for architecturally unallocated cpufeature ID
  * register with encoding Op0=3, Op1=0, CRn=0, CRm=crm, Op2=op2
  * (1 <= crm < 8, 0 <= Op2 < 8).
  */
 #define ID_UNALLOCATED(crm, op2) {			\
 	Op0(3), Op1(0), CRn(0), CRm(crm), Op2(op2),	\
-	.access = access_raz_id_reg,			\
-	.get_user = get_raz_reg,			\
-	.set_user = set_raz_id_reg,			\
+	.access = access_id_reg,			\
+	.get_user = get_id_reg,				\
+	.set_user = set_id_reg,				\
+	.visibility = raz_visibility			\
 }
 
 /*
@@ -1386,9 +1374,10 @@ static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
  */
 #define ID_HIDDEN(name) {			\
 	SYS_DESC(SYS_##name),			\
-	.access = access_raz_id_reg,		\
-	.get_user = get_raz_reg,		\
-	.set_user = set_raz_id_reg,		\
+	.access = access_id_reg,		\
+	.get_user = get_id_reg,			\
+	.set_user = set_id_reg,			\
+	.visibility = raz_visibility,		\
 }
 
 /*
@@ -1452,33 +1441,33 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 
 	/* AArch64 mappings of the AArch32 ID registers */
 	/* CRm=1 */
-	ID_SANITISED(ID_PFR0_EL1),
-	ID_SANITISED(ID_PFR1_EL1),
-	ID_SANITISED(ID_DFR0_EL1),
+	AA32_ID_SANITISED(ID_PFR0_EL1),
+	AA32_ID_SANITISED(ID_PFR1_EL1),
+	AA32_ID_SANITISED(ID_DFR0_EL1),
 	ID_HIDDEN(ID_AFR0_EL1),
-	ID_SANITISED(ID_MMFR0_EL1),
-	ID_SANITISED(ID_MMFR1_EL1),
-	ID_SANITISED(ID_MMFR2_EL1),
-	ID_SANITISED(ID_MMFR3_EL1),
+	AA32_ID_SANITISED(ID_MMFR0_EL1),
+	AA32_ID_SANITISED(ID_MMFR1_EL1),
+	AA32_ID_SANITISED(ID_MMFR2_EL1),
+	AA32_ID_SANITISED(ID_MMFR3_EL1),
 
 	/* CRm=2 */
-	ID_SANITISED(ID_ISAR0_EL1),
-	ID_SANITISED(ID_ISAR1_EL1),
-	ID_SANITISED(ID_ISAR2_EL1),
-	ID_SANITISED(ID_ISAR3_EL1),
-	ID_SANITISED(ID_ISAR4_EL1),
-	ID_SANITISED(ID_ISAR5_EL1),
-	ID_SANITISED(ID_MMFR4_EL1),
-	ID_SANITISED(ID_ISAR6_EL1),
+	AA32_ID_SANITISED(ID_ISAR0_EL1),
+	AA32_ID_SANITISED(ID_ISAR1_EL1),
+	AA32_ID_SANITISED(ID_ISAR2_EL1),
+	AA32_ID_SANITISED(ID_ISAR3_EL1),
+	AA32_ID_SANITISED(ID_ISAR4_EL1),
+	AA32_ID_SANITISED(ID_ISAR5_EL1),
+	AA32_ID_SANITISED(ID_MMFR4_EL1),
+	AA32_ID_SANITISED(ID_ISAR6_EL1),
 
 	/* CRm=3 */
-	ID_SANITISED(MVFR0_EL1),
-	ID_SANITISED(MVFR1_EL1),
-	ID_SANITISED(MVFR2_EL1),
+	AA32_ID_SANITISED(MVFR0_EL1),
+	AA32_ID_SANITISED(MVFR1_EL1),
+	AA32_ID_SANITISED(MVFR2_EL1),
 	ID_UNALLOCATED(3,3),
-	ID_SANITISED(ID_PFR2_EL1),
+	AA32_ID_SANITISED(ID_PFR2_EL1),
 	ID_HIDDEN(ID_DFR1_EL1),
-	ID_SANITISED(ID_MMFR5_EL1),
+	AA32_ID_SANITISED(ID_MMFR5_EL1),
 	ID_UNALLOCATED(3,7),
 
 	/* AArch64 ID registers */
@@ -2809,6 +2798,9 @@ int kvm_sys_reg_set_user(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg,
 	if (!r)
 		return -ENOENT;
 
+	if (sysreg_user_write_ignore(vcpu, r))
+		return 0;
+
 	if (r->set_user) {
 		ret = (r->set_user)(vcpu, r, val);
 	} else {

arch/arm64/kvm/sys_regs.h

@@ -86,6 +86,7 @@ struct sys_reg_desc {
 
 #define REG_HIDDEN		(1 << 0) /* hidden from userspace and guest */
 #define REG_RAZ			(1 << 1) /* RAZ from userspace and guest */
+#define REG_USER_WI		(1 << 2) /* WI from userspace only */
 
 static __printf(2, 3)
 inline void print_sys_reg_msg(const struct sys_reg_params *p,
@@ -136,22 +137,31 @@ static inline void reset_val(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r
 	__vcpu_sys_reg(vcpu, r->reg) = r->val;
 }
 
-static inline bool sysreg_hidden(const struct kvm_vcpu *vcpu,
-				 const struct sys_reg_desc *r)
+static inline unsigned int sysreg_visibility(const struct kvm_vcpu *vcpu,
+					     const struct sys_reg_desc *r)
 {
 	if (likely(!r->visibility))
-		return false;
+		return 0;
 
-	return r->visibility(vcpu, r) & REG_HIDDEN;
+	return r->visibility(vcpu, r);
+}
+
+static inline bool sysreg_hidden(const struct kvm_vcpu *vcpu,
+				 const struct sys_reg_desc *r)
+{
+	return sysreg_visibility(vcpu, r) & REG_HIDDEN;
 }
 
 static inline bool sysreg_visible_as_raz(const struct kvm_vcpu *vcpu,
 					 const struct sys_reg_desc *r)
 {
-	if (likely(!r->visibility))
-		return false;
+	return sysreg_visibility(vcpu, r) & REG_RAZ;
+}
 
-	return r->visibility(vcpu, r) & REG_RAZ;
+static inline bool sysreg_user_write_ignore(const struct kvm_vcpu *vcpu,
+					    const struct sys_reg_desc *r)
+{
+	return sysreg_visibility(vcpu, r) & REG_USER_WI;
 }
 
 static inline int cmp_sys_reg(const struct sys_reg_desc *i1,

tools/testing/selftests/kvm/.gitignore

@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
+/aarch64/aarch32_id_regs
 /aarch64/arch_timer
 /aarch64/debug-exceptions
 /aarch64/get-reg-list

tools/testing/selftests/kvm/Makefile

@@ -144,6 +144,7 @@ TEST_GEN_PROGS_x86_64 += system_counter_offset_test
 # Compiled outputs used by test targets
 TEST_GEN_PROGS_EXTENDED_x86_64 += x86_64/nx_huge_pages_test
 
+TEST_GEN_PROGS_aarch64 += aarch64/aarch32_id_regs
 TEST_GEN_PROGS_aarch64 += aarch64/arch_timer
 TEST_GEN_PROGS_aarch64 += aarch64/debug-exceptions
 TEST_GEN_PROGS_aarch64 += aarch64/get-reg-list