[PATCH v2 3/6] KVM: arm64: Allow guest to set the OSLK bit

[Oliver Upton]

Allow writes to OSLAR and forward the OSLK bit to OSLSR. Change the
reset value of the OSLK bit to 1. Allow the value to be migrated by
making OSLSR_EL1.OSLK writable from userspace.

Signed-off-by: Oliver Upton <oupton at google.com>
---
 arch/arm64/include/asm/sysreg.h |  6 ++++++
 arch/arm64/kvm/sys_regs.c       | 35 +++++++++++++++++++++++++--------
 2 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index b268082d67ed..6ba4dc97b69d 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -127,7 +127,13 @@
 #define SYS_DBGWCRn_EL1(n)		sys_reg(2, 0, 0, n, 7)
 #define SYS_MDRAR_EL1			sys_reg(2, 0, 1, 0, 0)
 #define SYS_OSLAR_EL1			sys_reg(2, 0, 1, 0, 4)
+
+#define SYS_OSLAR_OSLK			BIT(0)
+
 #define SYS_OSLSR_EL1			sys_reg(2, 0, 1, 1, 4)
+
+#define SYS_OSLSR_OSLK			BIT(1)
+
 #define SYS_OSDLR_EL1			sys_reg(2, 0, 1, 3, 4)
 #define SYS_DBGPRCR_EL1			sys_reg(2, 0, 1, 4, 4)
 #define SYS_DBGCLAIMSET_EL1		sys_reg(2, 0, 7, 8, 6)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 0326b3df0736..acd8aa2e5a44 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -44,6 +44,10 @@
  * 64bit interface.
  */
 
+static int reg_from_user(u64 *val, const void __user *uaddr, u64 id);
+static int reg_to_user(void __user *uaddr, const u64 *val, u64 id);
+static u64 sys_reg_to_index(const struct sys_reg_desc *reg);
+
 static bool read_from_write_only(struct kvm_vcpu *vcpu,
 				 struct sys_reg_params *params,
 				 const struct sys_reg_desc *r)
@@ -287,6 +291,24 @@ static bool trap_loregion(struct kvm_vcpu *vcpu,
 	return trap_raz_wi(vcpu, p, r);
 }
 
+static bool trap_oslar_el1(struct kvm_vcpu *vcpu,
+			   struct sys_reg_params *p,
+			   const struct sys_reg_desc *r)
+{
+	u64 oslsr;
+
+	if (!p->is_write)
+		return read_from_write_only(vcpu, p, r);
+
+	/* Forward the OSLK bit to OSLSR */
+	oslsr = __vcpu_sys_reg(vcpu, OSLSR_EL1) & ~SYS_OSLSR_OSLK;
+	if (p->regval & SYS_OSLAR_OSLK)
+		oslsr |= SYS_OSLSR_OSLK;
+
+	__vcpu_sys_reg(vcpu, OSLSR_EL1) = oslsr;
+	return true;
+}
+
 static bool trap_oslsr_el1(struct kvm_vcpu *vcpu,
 			   struct sys_reg_params *p,
 			   const struct sys_reg_desc *r)
@@ -309,9 +331,10 @@ static int set_oslsr_el1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 	if (err)
 		return err;
 
-	if (val != rd->val)
+	if ((val | SYS_OSLSR_OSLK) != rd->val)
 		return -EINVAL;
 
+	__vcpu_sys_reg(vcpu, rd->reg) = val;
 	return 0;
 }
 
@@ -1176,10 +1199,6 @@ static bool access_raz_id_reg(struct kvm_vcpu *vcpu,
 	return __access_id_reg(vcpu, p, r, true);
 }
 
-static int reg_from_user(u64 *val, const void __user *uaddr, u64 id);
-static int reg_to_user(void __user *uaddr, const u64 *val, u64 id);
-static u64 sys_reg_to_index(const struct sys_reg_desc *reg);
-
 /* Visibility overrides for SVE-specific control registers */
 static unsigned int sve_visibility(const struct kvm_vcpu *vcpu,
 				   const struct sys_reg_desc *rd)
@@ -1456,8 +1475,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	DBG_BCR_BVR_WCR_WVR_EL1(15),
 
 	{ SYS_DESC(SYS_MDRAR_EL1), trap_raz_wi },
-	{ SYS_DESC(SYS_OSLAR_EL1), trap_raz_wi },
-	{ SYS_DESC(SYS_OSLSR_EL1), trap_oslsr_el1, reset_val, OSLSR_EL1, 0x00000008,
+	{ SYS_DESC(SYS_OSLAR_EL1), trap_oslar_el1 },
+	{ SYS_DESC(SYS_OSLSR_EL1), trap_oslsr_el1, reset_val, OSLSR_EL1, 0x0000000A,
 		.set_user = set_oslsr_el1, },
 	{ SYS_DESC(SYS_OSDLR_EL1), trap_raz_wi },
 	{ SYS_DESC(SYS_DBGPRCR_EL1), trap_raz_wi },
@@ -1930,7 +1949,7 @@ static const struct sys_reg_desc cp14_regs[] = {
 
 	DBGBXVR(0),
 	/* DBGOSLAR */
-	{ Op1( 0), CRn( 1), CRm( 0), Op2( 4), trap_raz_wi },
+	{ Op1( 0), CRn( 1), CRm( 0), Op2( 4), trap_oslar_el1 },
 	DBGBXVR(1),
 	/* DBGOSLSR */
 	{ Op1( 0), CRn( 1), CRm( 1), Op2( 4), trap_oslsr_el1, NULL, OSLSR_EL1 },
-- 
2.33.1.1089.g2158813163f-goog