Re: [Qemu-devel] [PATCH RFC v3 13/14] intel_iommu: allow dynamic switch of IOMMU region

[Jason Wang]

On 2017年01月16日 15:50, Peter Xu wrote:
> On Mon, Jan 16, 2017 at 02:20:31PM +0800, Jason Wang wrote:
>
> [...]
>
> > > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > > index fd75112..2596f11 100644
> > > --- a/hw/i386/intel_iommu.c
> > > +++ b/hw/i386/intel_iommu.c
> > > @@ -1343,9 +1343,49 @@ static void vtd_handle_gcmd_sirtp(IntelIOMMUState *s)
> > >       vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_IRTPS);
> > >   }
> > > +static void vtd_switch_address_space(VTDAddressSpace *as, bool iommu_enabled)
> > Looks like you can check s->dmar_enabled here?
> Yes, we need to check old state in case we don't need a switch at all.
> Actually I checked it...

I mean is there a chance that iommu_enabled( better name should be 
dmar_enabled) is not equal to s->dmar_enabled? Looks not.

vtd_handle_gcmd_te() did:

    ...
    if (en) {
        s->dmar_enabled = true;
        /* Ok - report back to driver */
        vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_TES);
    } else {
        s->dmar_enabled = false;
    ...

You can vtd_switch_address_space_all(s, en) after this which will call 
this function. And another caller like you've pointed out has already 
call this through s->dmar_enabled. So en here is always s->dmar_enalbed?

Thanks