[v8,28/69] KVM: arm64: nv: Allow a sysreg to be hidden from userspace only

Commit Message

Marc Zyngier Jan. 31, 2023, 9:24 a.m. UTC

So far, we never needed to distinguish between registers hidden
from userspace and being hidden from a guest (they are always
either visible to both, or hidden from both).

With NV, we have the ugly case of the EL02 and EL12 registers,
which are only a view on the EL0 and EL1 registers. It makes
absolutely no sense to expose them to userspace, since it
already has the canonical view.

Add a new visibility flag (REG_HIDDEN_USER) and a new helper that
checks for it and REG_HIDDEN when checking whether to expose
a sysreg to userspace. Subsequent patches will make use of it.

Reviewed-by: Alexandru Elisei <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
---
 arch/arm64/kvm/sys_regs.c |  6 +++---
 arch/arm64/kvm/sys_regs.h | 14 ++++++++++++--
 2 files changed, 15 insertions(+), 5 deletions(-)

Patch

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 732d622f5fab..eff4d41bf1bb 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -3341,7 +3341,7 @@  int kvm_sys_reg_get_user(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg,
 	int ret;
 
 	r = id_to_sys_reg_desc(vcpu, reg->id, table, num);
-	if (!r)
+	if (!r || sysreg_hidden_user(vcpu, r))
 		return -ENOENT;
 
 	if (r->get_user) {
@@ -3385,7 +3385,7 @@  int kvm_sys_reg_set_user(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg,
 		return -EFAULT;
 
 	r = id_to_sys_reg_desc(vcpu, reg->id, table, num);
-	if (!r)
+	if (!r || sysreg_hidden_user(vcpu, r))
 		return -ENOENT;
 
 	if (sysreg_user_write_ignore(vcpu, r))
@@ -3471,7 +3471,7 @@  static int walk_one_sys_reg(const struct kvm_vcpu *vcpu,
 	if (!(rd->reg || rd->get_user))
 		return 0;
 
-	if (sysreg_hidden(vcpu, rd))
+	if (sysreg_hidden_user(vcpu, rd))
 		return 0;
 
 	if (!copy_reg_to_user(rd, uind))
diff --git a/arch/arm64/kvm/sys_regs.h b/arch/arm64/kvm/sys_regs.h
index e4ebb3a379fd..6b11f2cc7146 100644
--- a/arch/arm64/kvm/sys_regs.h
+++ b/arch/arm64/kvm/sys_regs.h
@@ -85,8 +85,9 @@  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 */
+#define REG_HIDDEN_USER		(1 << 1) /* hidden from userspace only */
+#define REG_RAZ			(1 << 2) /* RAZ from userspace and guest */
+#define REG_USER_WI		(1 << 3) /* WI from userspace only */
 
 static __printf(2, 3)
 inline void print_sys_reg_msg(const struct sys_reg_params *p,
@@ -152,6 +153,15 @@  static inline bool sysreg_hidden(const struct kvm_vcpu *vcpu,
 	return sysreg_visibility(vcpu, r) & REG_HIDDEN;
 }
 
+static inline bool sysreg_hidden_user(const struct kvm_vcpu *vcpu,
+				      const struct sys_reg_desc *r)
+{
+	if (likely(!r->visibility))
+		return false;
+
+	return r->visibility(vcpu, r) & (REG_HIDDEN | REG_HIDDEN_USER);
+}
+
 static inline bool sysreg_visible_as_raz(const struct kvm_vcpu *vcpu,
 					 const struct sys_reg_desc *r)
 {