Re: [PATCH v3 2/2] KVM: arm64: Fix exclusive limit for IPA size

[Andrew Jones <drjones@redhat.com>]

On Thu, Mar 11, 2021 at 10:00:16AM +0000, Marc Zyngier wrote:
> When registering a memslot, we check the size and location of that
> memslot against the IPA size to ensure that we can provide guest
> access to the whole of the memory.
> 
> Unfortunately, this check rejects memslot that end-up at the exact
> limit of the addressing capability for a given IPA size. For example,
> it refuses the creation of a 2GB memslot at 0x8000000 with a 32bit
> IPA space.
> 
> Fix it by relaxing the check to accept a memslot reaching the
> limit of the IPA space.
> 
> Fixes: e55cac5bf2a9 ("kvm: arm/arm64: Prepare for VM specific stage2 translations")

Isn't this actually fixing commit c3058d5da222 ("arm/arm64: KVM: Ensure
memslots are within KVM_PHYS_SIZE") ?

> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Cc: stable@vger.kernel.org
> ---
>  arch/arm64/kvm/mmu.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 77cb2d28f2a4..8711894db8c2 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1312,8 +1312,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>  	 * Prevent userspace from creating a memory region outside of the IPA
>  	 * space addressable by the KVM guest IPA space.
>  	 */
> -	if (memslot->base_gfn + memslot->npages >=
> -	    (kvm_phys_size(kvm) >> PAGE_SHIFT))
> +	if ((memslot->base_gfn + memslot->npages) > (kvm_phys_size(kvm) >> PAGE_SHIFT))
>  		return -EFAULT;
>  
>  	mmap_read_lock(current->mm);
> -- 
> 2.29.2
> 

Otherwise

Reviewed-by: Andrew Jones <drjones@redhat.com>

Thanks,
drew