KVM: ARM: Handle I/O aborts

When the guest accesses I/O memory this will create data abort
exceptions and they are handled by decoding the HSR information
(physical address, read/write, length, register) and forwarding reads
and writes to QEMU which performs the device emulation.

Certain classes of load/store operations do not support the syndrome
information provided in the HSR.  We don't support decoding these (patches
are available elsewhere), so we report an error to user space in this case.

This requires changing the general flow somewhat since new calls to run
the VCPU must check if there's a pending MMIO load and perform the write
after userspace has made the data available.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/arch/arm/kvm/trace.h b/arch/arm/kvm/trace.h
index 624b5a4e8fad..a8e73ed5ad5b 100644
--- a/arch/arm/kvm/trace.h
+++ b/arch/arm/kvm/trace.h
@@ -90,6 +90,27 @@ TRACE_EVENT(kvm_irq_line,
                   __entry->type, __entry->vcpu_idx, __entry->irq_num, __entry->level)
 );
 
+TRACE_EVENT(kvm_mmio_emulate,
+        TP_PROTO(unsigned long vcpu_pc, unsigned long instr,
+                 unsigned long cpsr),
+        TP_ARGS(vcpu_pc, instr, cpsr),
+
+        TP_STRUCT__entry(
+                __field(        unsigned long,  vcpu_pc         )
+                __field(        unsigned long,  instr           )
+                __field(        unsigned long,  cpsr            )
+        ),
+
+        TP_fast_assign(
+                __entry->vcpu_pc                = vcpu_pc;
+                __entry->instr                  = instr;
+                __entry->cpsr                   = cpsr;
+        ),
+
+        TP_printk("Emulate MMIO at: 0x%08lx (instr: %08lx, cpsr: %08lx)",
+                  __entry->vcpu_pc, __entry->instr, __entry->cpsr)
+);
+
 /* Architecturally implementation defined CP15 register access */
 TRACE_EVENT(kvm_emulate_cp15_imp,
         TP_PROTO(unsigned long Op1, unsigned long Rt1, unsigned long CRn,