| Message ID | 20231026205306.3045075-1-oliver.upton@linux.dev (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] KVM: arm64: Add tracepoint for MMIO accesses where ISV==0 | expand |
On 2023/10/27 4:53, Oliver Upton wrote: > 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. > > Signed-off-by: Oliver Upton <oliver.upton@linux.dev> Acked-by: Zenghui Yu <yuzenghui@huawei.com>
On Thu, 26 Oct 2023 21:53:06 +0100, Oliver Upton <oliver.upton@linux.dev> wrote: > > 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. > > Signed-off-by: Oliver Upton <oliver.upton@linux.dev> Acked-by: Marc Zyngier <maz@kernel.org> Thanks for going the extra mile on this! M.
diff --git a/arch/arm64/kvm/mmio.c b/arch/arm64/kvm/mmio.c index 3dd38a151d2a..200c8019a82a 100644 --- 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 8ad53104934d..c18c1a95831e 100644 --- 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),
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. Signed-off-by: Oliver Upton <oliver.upton@linux.dev> --- v1: https://lore.kernel.org/kvmarm/ZToh7pNhz1zzQw6C@linux.dev/ v1 -> v2: - Add a tracepoint to improve debuggability (Marc) Tested with the page_fault_test selftest, which does pre-indexed accesses outside of a memslot. arch/arm64/kvm/mmio.c | 4 +++- arch/arm64/kvm/trace_arm.h | 25 +++++++++++++++++++++++++ 2 files changed, 28 insertions(+), 1 deletion(-) base-commit: 6465e260f48790807eef06b583b38ca9789b6072