Re: [PATCH v3 02/10] KVM: arm64: vgic-v3: Check redist region is not above the VM IPA size

[Ricardo Koller <ricarkol@google.com>]

Hi Eric,

On Wed, Sep 29, 2021 at 06:23:04PM +0200, Eric Auger wrote:
> Hi Ricardo,
> 
> On 9/28/21 8:47 PM, Ricardo Koller wrote:
> > Verify that the redistributor regions do not extend beyond the
> > VM-specified IPA range (phys_size). This can happen when using
> > KVM_VGIC_V3_ADDR_TYPE_REDIST or KVM_VGIC_V3_ADDR_TYPE_REDIST_REGIONS
> > with:
> >
> >   base + size > phys_size AND base < phys_size
> >
> > Add the missing check into vgic_v3_alloc_redist_region() which is called
> > when setting the regions, and into vgic_v3_check_base() which is called
> > when attempting the first vcpu-run. The vcpu-run check does not apply to
> > KVM_VGIC_V3_ADDR_TYPE_REDIST_REGIONS because the regions size is known
> > before the first vcpu-run. Note that using the REDIST_REGIONS API
> > results in a different check, which already exists, at first vcpu run:
> > that the number of redist regions is enough for all vcpus.
> >
> > Finally, this patch also enables some extra tests in
> > vgic_v3_alloc_redist_region() by calculating "size" early for the legacy
> > redist api: like checking that the REDIST region can fit all the already
> > created vcpus.
> >
> > Signed-off-by: Ricardo Koller <ricarkol@google.com>
> > ---
> >  arch/arm64/kvm/vgic/vgic-mmio-v3.c | 6 ++++--
> >  arch/arm64/kvm/vgic/vgic-v3.c      | 4 ++++
> >  2 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> > index a09cdc0b953c..9be02bf7865e 100644
> > --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> > +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> > @@ -796,7 +796,9 @@ static int vgic_v3_alloc_redist_region(struct kvm *kvm, uint32_t index,
> >  	struct vgic_dist *d = &kvm->arch.vgic;
> >  	struct vgic_redist_region *rdreg;
> >  	struct list_head *rd_regions = &d->rd_regions;
> > -	size_t size = count * KVM_VGIC_V3_REDIST_SIZE;
> > +	int nr_vcpus = atomic_read(&kvm->online_vcpus);
> > +	size_t size = count ? count * KVM_VGIC_V3_REDIST_SIZE
> > +			    : nr_vcpus * KVM_VGIC_V3_REDIST_SIZE;
> 
> This actually fixes the  vgic_dist_overlap(kvm, base, size=0)
> 
> in case the number of online-vcpus at that time is less than the final
> one (1st run), if count=0 (legacy API) do we ever check that the RDIST
> (with accumulated vcpu rdists) does not overlap with dist.
> in other words shouldn't we call vgic_dist_overlap(kvm, base, size)
> again in vgic_v3_check_base().
> 

I think we're good; that's checked by vgic_v3_rdist_overlap(dist_base)
in vgic_v3_check_base(). This function uses the only region (legacy
case) using a size based on the online_vcpus (in
vgic_v3_rd_region_size()).  This exact situation is tested by
test_vgic_then_vcpus() in the vgic_init selftest.

Thanks,
Ricardo

> Thanks
> 
> Eric
> 
> >  	int ret;
> >  
> >  	/* cross the end of memory ? */
> > @@ -840,7 +842,7 @@ static int vgic_v3_alloc_redist_region(struct kvm *kvm, uint32_t index,
> >  
> >  	rdreg->base = VGIC_ADDR_UNDEF;
> >  
> > -	ret = vgic_check_ioaddr(kvm, &rdreg->base, base, SZ_64K);
> > +	ret = vgic_check_iorange(kvm, &rdreg->base, base, SZ_64K, size);
> >  	if (ret)
> >  		goto free;
> >  
> > diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
> > index 21a6207fb2ee..27ee674631b3 100644
> > --- a/arch/arm64/kvm/vgic/vgic-v3.c
> > +++ b/arch/arm64/kvm/vgic/vgic-v3.c
> > @@ -486,6 +486,10 @@ bool vgic_v3_check_base(struct kvm *kvm)
> >  		if (rdreg->base + vgic_v3_rd_region_size(kvm, rdreg) <
> >  			rdreg->base)
> >  			return false;
> > +
> > +		if (rdreg->base + vgic_v3_rd_region_size(kvm, rdreg) >
> > +			kvm_phys_size(kvm))
> > +			return false;
> >  	}
> >  
> >  	if (IS_VGIC_ADDR_UNDEF(d->vgic_dist_base))
>