On Mon, Jan 12, 2015 at 6:21 PM, Eric Auger <eric.auger@xxxxxxxxxx> wrote:
>
> On 12/05/2014 01:06 PM, Nikolay Nikolaev wrote:
> > On Sat, Nov 29, 2014 at 1:28 PM, Christoffer Dall
> > <christoffer.dall@xxxxxxxxxx> wrote:
> >> On Mon, Nov 24, 2014 at 11:26:51PM +0200, Nikolay Nikolaev wrote:
> >>> On IO memory abort, try to handle the MMIO access thorugh the KVM
> >>> registered read/write callbacks. This is done by invoking the relevant
> >>> kvm_io_bus_* API.
> >>>
> >>> Signed-off-by: Nikolay Nikolaev <n.nikolaev@xxxxxxxxxxxxxxxxxxxxxx>
> >>> ---
> >>> arch/arm/kvm/mmio.c | 33 +++++++++++++++++++++++++++++++++
> >>> 1 file changed, 33 insertions(+)
> >>>
> >>> diff --git a/arch/arm/kvm/mmio.c b/arch/arm/kvm/mmio.c
> >>> index 4cb5a93..81230da 100644
> >>> --- a/arch/arm/kvm/mmio.c
> >>> +++ b/arch/arm/kvm/mmio.c
> >>> @@ -162,6 +162,36 @@ static int decode_hsr(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> >>> return 0;
> >>> }
> >>>
> >>> +/**
> >>> + * kvm_handle_mmio - handle an in-kernel MMIO access
> >>> + * @vcpu: pointer to the vcpu performing the access
> >>> + * @run: pointer to the kvm_run structure
> >>> + * @mmio: pointer to the data describing the access
> >>> + *
> >>> + * returns true if the MMIO access has been performed in kernel space,
> >>> + * and false if it needs to be emulated in user space.
> >>> + */
> >>> +static bool handle_kernel_mmio(struct kvm_vcpu *vcpu, struct kvm_run *run,
> >>> + struct kvm_exit_mmio *mmio)
> >>> +{
> >>> + int ret;
> >>> +
> >>> + if (mmio->is_write) {
> >>> + ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, mmio->phys_addr,
> >>> + mmio->len, &mmio->data);
> >>> +
> >>> + } else {
> >>> + ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, mmio->phys_addr,
> >>> + mmio->len, &mmio->data);
> >>> + }
> >>> + if (!ret) {
> >>> + kvm_prepare_mmio(run, mmio);
> >>> + kvm_handle_mmio_return(vcpu, run);
> >>> + }
> >>> +
> >>> + return !ret;
> >>> +}
> >>> +
> >>> int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
> >>> phys_addr_t fault_ipa)
> >>> {
> >>> @@ -200,6 +230,9 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
> >>> if (vgic_handle_mmio(vcpu, run, &mmio))
> >>> return 1;
> >>>
> >>> + if (handle_kernel_mmio(vcpu, run, &mmio))
> >>> + return 1;
> >>> +
> >>
> >> Is this stuff always synchronously handled so that the mmio is properly
> >> populated upon handle_kernel_mmio on reads?
> >
> > If I get it right the kvm_io_bus_ API is intended to work
> > synchronously. Of course it probably depends
> > on how the registered device handles the read/write call.
> > Or maybe I misunderstand your question? Please clarify in that case.
>
> in case of ioeventfd implementation it is not the case since the write
> is deferred in the kernel thread which handles the eventfd.
Christofer was asking about reads. I guess about writes it does not
make any diiference as long as the needed values are copied into the
new thread.
regards,
Nikolay Nikolaev
>
> Best Regards
>
> Eric
> >
> > regards,
> > Nikolay Nikolaev
> >
> >>
> >> -Christoffer
>
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