Re: [PATCH v4 5/6] hw/arm/virt: Disable highmem devices that don't fit in the PA range

[Marc Zyngier]

On Mon, 10 Jan 2022 17:12:50 +0000,
Eric Auger <eric.auger@redhat.com> wrote:
> 
> Hi Marc,
> 
> On 1/7/22 5:33 PM, Marc Zyngier wrote:
> > In order to only keep the highmem devices that actually fit in
> > the PA range, check their location against the range and update
> > highest_gpa if they fit. If they don't, mark them them as disabled.
> s/them them/them
> >
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > ---
> >  hw/arm/virt.c | 34 ++++++++++++++++++++++++++++------
> >  1 file changed, 28 insertions(+), 6 deletions(-)
> >
> > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > index db4b0636e1..70b4773b3e 100644
> > --- a/hw/arm/virt.c
> > +++ b/hw/arm/virt.c
> > @@ -1711,21 +1711,43 @@ static void virt_set_memmap(VirtMachineState *vms, 
> > int pa_bits)
> >          base = vms->memmap[VIRT_MEM].base + LEGACY_RAMLIMIT_BYTES;
> >      }
> >  
> > +    /* We know for sure that at least the memory fits in the PA space */
> > +    vms->highest_gpa = memtop - 1;
> > +
> >      for (i = VIRT_LOWMEMMAP_LAST; i < ARRAY_SIZE(extended_memmap); i++) {
> >          hwaddr size = extended_memmap[i].size;
> > +        bool fits;
> >  
> >          base = ROUND_UP(base, size);
> >          vms->memmap[i].base = base;
> >          vms->memmap[i].size = size;
> > +
> > +        /*
> > +         * Check each device to see if they fit in the PA space,
> > +         * moving highest_gpa as we go.
> > +         *
> > +         * For each device that doesn't fit, disable it.
> > +         */
> > +        fits = (base + size) <= BIT_ULL(pa_bits);
> > +        if (fits) {
> > +            vms->highest_gpa = MAX(vms->highest_gpa, base + size - 1);
> why do you need the MAX()?

Well spotted, I don't. Since we build the memmap by moving base
upward, I can directly use 'base + size - 1' as the new highest_gpa
value.

Thanks,

        M.

-- 
Without deviation from the norm, progress is not possible.