KVM: arm64: Add tracepoint for MMIO accesses where ISV==0

It is a pretty well known fact that KVM does not support MMIO emulation
without valid instruction syndrome information (ESR_EL2.ISV == 0). The
current kvm_pr_unimpl() is pretty useless, as it contains zero context
to relate the event to a vCPU.

Replace it with a precise tracepoint that dumps the relevant context
so the user can make sense of what the guest is doing.

Acked-by: Zenghui Yu <yuzenghui@huawei.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231026205306.3045075-1-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/kvm/mmio.c b/arch/arm64/kvm/mmio.c
index 3dd38a151d2a683c6f5e15c2b918ec663cf0f5cc..200c8019a82a4380b6c338fe2ec0ac0c50d0512b 100644 (file)
--- a/arch/arm64/kvm/mmio.c
+++ b/arch/arm64/kvm/mmio.c
@@ -135,6 +135,9 @@ int io_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
         * volunteered to do so, and bail out otherwise.
         */
        if (!kvm_vcpu_dabt_isvalid(vcpu)) {
+               trace_kvm_mmio_nisv(*vcpu_pc(vcpu), kvm_vcpu_get_esr(vcpu),
+                                   kvm_vcpu_get_hfar(vcpu), fault_ipa);
+
                if (test_bit(KVM_ARCH_FLAG_RETURN_NISV_IO_ABORT_TO_USER,
                             &vcpu->kvm->arch.flags)) {
                        run->exit_reason = KVM_EXIT_ARM_NISV;
@@ -143,7 +146,6 @@ int io_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
                        return 0;
                }
 
-               kvm_pr_unimpl("Data abort outside memslots with no valid syndrome info\n");
                return -ENOSYS;
        }
 

diff --git a/arch/arm64/kvm/trace_arm.h b/arch/arm64/kvm/trace_arm.h
index 8ad53104934dcdfdc892852ce4f67cb1d0138f52..c18c1a95831e1bb9bef1fa167d54527a3da3cc45 100644 (file)
--- a/arch/arm64/kvm/trace_arm.h
+++ b/arch/arm64/kvm/trace_arm.h
@@ -136,6 +136,31 @@ TRACE_EVENT(kvm_mmio_emulate,
                  __entry->vcpu_pc, __entry->instr, __entry->cpsr)
 );
 
+TRACE_EVENT(kvm_mmio_nisv,
+       TP_PROTO(unsigned long vcpu_pc, unsigned long esr,
+                unsigned long far, unsigned long ipa),
+       TP_ARGS(vcpu_pc, esr, far, ipa),
+
+       TP_STRUCT__entry(
+               __field(        unsigned long,  vcpu_pc         )
+               __field(        unsigned long,  esr             )
+               __field(        unsigned long,  far             )
+               __field(        unsigned long,  ipa             )
+       ),
+
+       TP_fast_assign(
+               __entry->vcpu_pc                = vcpu_pc;
+               __entry->esr                    = esr;
+               __entry->far                    = far;
+               __entry->ipa                    = ipa;
+       ),
+
+       TP_printk("ipa %#016lx, esr %#016lx, far %#016lx, pc %#016lx",
+                 __entry->ipa, __entry->esr,
+                 __entry->far, __entry->vcpu_pc)
+);
+
+
 TRACE_EVENT(kvm_set_way_flush,
            TP_PROTO(unsigned long vcpu_pc, bool cache),
            TP_ARGS(vcpu_pc, cache),