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

[Eric Auger <eric.auger@redhat.com>]

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().

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))

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