[PATCH 4/8] KVM: arm64: nv: Treat the VNCR GICv3 registers as hidden from user

[Oliver Upton <oupton@kernel.org>]

KVM's emulation of sysreg traps will soon need to evaluate the
visibility of a sysreg prior to the effects of the L1 hypervisor's traps
to cope with instructions that intersect with a CGT but lack a
corresponding FGU bit (I know, not enough TLAs).

The VNCR GICv3 registers are marked as hidden from both user/guest on
the basis that KVM never handles these traps locally and unconditinally
relies on VNCR redirection. But an L1 hypervisor could trap these.

Remap the visibility as being specific to user accesses, giving the
indication that guest accesses to the sysreg are legal at least from an
architecture POV. Note that the guest side of the visibility was a bit
belt-and-braces as the bad_vncr_trap() accessor will act as a backstop
against any unexpected local trap handling.

Signed-off-by: Oliver Upton <oupton@kernel.org>
---
 arch/arm64/kvm/sys_regs.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 870dcb25d0d7..0b21b454242c 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1020,10 +1020,10 @@ static u64 reset_mpidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
 	return mpidr;
 }
 
-static unsigned int hidden_visibility(const struct kvm_vcpu *vcpu,
-				      const struct sys_reg_desc *r)
+static unsigned int hidden_user_visibility(const struct kvm_vcpu *vcpu,
+					   const struct sys_reg_desc *r)
 {
-	return REG_HIDDEN;
+	return REG_USER_HIDDEN;
 }
 
 static unsigned int pmu_visibility(const struct kvm_vcpu *vcpu,
@@ -2757,7 +2757,7 @@ static bool bad_redir_trap(struct kvm_vcpu *vcpu,
 #define EL2_REG_VNCR_FILT(name, vis)			\
 	EL2_REG_FILTERED(name, bad_vncr_trap, reset_val, 0, vis)
 #define EL2_REG_VNCR_GICv3(name)			\
-	EL2_REG_VNCR_FILT(name, hidden_visibility)
+	EL2_REG_VNCR_FILT(name, hidden_user_visibility)
 #define EL2_REG_REDIR(name, rst, v)	EL2_REG(name, bad_redir_trap, rst, v)
 
 #define TIMER_REG(name, vis)					   \
-- 
2.47.3