From mboxrd@z Thu Jan 1 00:00:00 1970 From: andre.przywara@arm.com (Andre Przywara) Date: Thu, 6 Nov 2014 12:11:45 +0000 Subject: [PATCH] arm/arm64: KVM: avoid unnecessary guest register mangling on MMIO read Message-ID: <1415275905-21409-1-git-send-email-andre.przywara@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Currently we mangle the endianness of the guest's register even on an MMIO _read_, where it is completely useless, because we will not use the value of that register. Rework the io_mem_abort() function to clearly separate between reads and writes and only do the endianness mangling on MMIO writes. Signed-off-by: Andre Przywara --- arch/arm/kvm/mmio.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) Hi, I found this while investigating bi-endianness for MMIO. Not sure if it's really useful, but I found it more clearer this way. Cheers, Andre. diff --git a/arch/arm/kvm/mmio.c b/arch/arm/kvm/mmio.c index 4cb5a93..5d3bfc0 100644 --- a/arch/arm/kvm/mmio.c +++ b/arch/arm/kvm/mmio.c @@ -187,15 +187,18 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run, } rt = vcpu->arch.mmio_decode.rt; - data = vcpu_data_guest_to_host(vcpu, *vcpu_reg(vcpu, rt), mmio.len); - trace_kvm_mmio((mmio.is_write) ? KVM_TRACE_MMIO_WRITE : - KVM_TRACE_MMIO_READ_UNSATISFIED, - mmio.len, fault_ipa, - (mmio.is_write) ? data : 0); + if (mmio.is_write) { + data = vcpu_data_guest_to_host(vcpu, *vcpu_reg(vcpu, rt), + mmio.len); - if (mmio.is_write) + trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, mmio.len, + fault_ipa, data); mmio_write_buf(mmio.data, mmio.len, data); + } else { + trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, mmio.len, + fault_ipa, 0); + } if (vgic_handle_mmio(vcpu, run, &mmio)) return 1; -- 1.7.9.5