KVM: arm64: nv: Add trap forwarding infrastructure

A significant part of what a NV hypervisor needs to do is to decide
whether a trap from a L2+ guest has to be forwarded to a L1 guest
or handled locally. This is done by checking for the trap bits that
the guest hypervisor has set and acting accordingly, as described by
the architecture.

A previous approach was to sprinkle a bunch of checks in all the
system register accessors, but this is pretty error prone and doesn't
help getting an overview of what is happening.

Instead, implement a set of global tables that describe a trap bit,
combinations of trap bits, behaviours on trap, and what bits must
be evaluated on a system register trap.

Although this is painful to describe, this allows to specify each
and every control bit in a static manner. To make it efficient,
the table is inserted in an xarray that is global to the system,
and checked each time we trap a system register while running
a L2 guest.

Add the basic infrastructure for now, while additional patches will
implement configuration registers.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Jing Zhang <jingzhangos@google.com>
Reviewed-by: Miguel Luis <miguel.luis@oracle.com>
Link: https://lore.kernel.org/r/20230815183903.2735724-15-maz@kernel.org

1 files changed, 26 insertions, 0 deletions

diff --git a/arch/arm64/kvm/trace_arm.h b/arch/arm64/kvm/trace_arm.h
index 6ce5c025218d..8ad53104934d 100644
--- a/arch/arm64/kvm/trace_arm.h
+++ b/arch/arm64/kvm/trace_arm.h
@@ -364,6 +364,32 @@ TRACE_EVENT(kvm_inject_nested_exception,
 		  __entry->hcr_el2)
 );
 
+TRACE_EVENT(kvm_forward_sysreg_trap,
+	    TP_PROTO(struct kvm_vcpu *vcpu, u32 sysreg, bool is_read),
+	    TP_ARGS(vcpu, sysreg, is_read),
+
+	    TP_STRUCT__entry(
+		__field(u64,	pc)
+		__field(u32,	sysreg)
+		__field(bool,	is_read)
+	    ),
+
+	    TP_fast_assign(
+		__entry->pc = *vcpu_pc(vcpu);
+		__entry->sysreg = sysreg;
+		__entry->is_read = is_read;
+	    ),
+
+	    TP_printk("%llx %c (%d,%d,%d,%d,%d)",
+		      __entry->pc,
+		      __entry->is_read ? 'R' : 'W',
+		      sys_reg_Op0(__entry->sysreg),
+		      sys_reg_Op1(__entry->sysreg),
+		      sys_reg_CRn(__entry->sysreg),
+		      sys_reg_CRm(__entry->sysreg),
+		      sys_reg_Op2(__entry->sysreg))
+);
+
 #endif /* _TRACE_ARM_ARM64_KVM_H */
 
 #undef TRACE_INCLUDE_PATH