Re: [PATCH 3/4] KVM: arm64: Fix address check for memory slot

[Gavin Shan]

Hi Keqian,

On 3/15/21 6:33 PM, Keqian Zhu wrote:
> FYI, this has been fixed by Marc in commit 262b003d059c.

Yeah, I didn't check 5.12.rc3 code where the issue has been
fixed. So please ignore this one and sorry for the noise.

Thanks,
Gavin
 
> On 2021/3/15 12:18, Gavin Shan wrote:
> > The last (IPA) page can't be specified when a new memory slot is
> > added. The error -EFAULT is returned when the memory slot is added
> > with the following parameters for the VM, which has 40-bits IPA
> > limit. The host has 4KB base page size. It's not correct because
> > the last (IPA) page is still usable.
> >
> >     struct kvm_userspace_memory_region {
> >        __u32 slot;               /* 1            */
> >        __u32 flags;              /* 0            */
> >        __u64 guest_phys_addr;    /* 0xfffffff000 */
> >        __u64 memory_size;        /* 0x1000       */
> >        __u64 userspace_addr;
> >     };
> >
> > Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
> > ---
> >   arch/arm64/kvm/mmu.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > index 286b603ed0d3..a5a8ade9fde4 100644
> > --- a/arch/arm64/kvm/mmu.c
> > +++ b/arch/arm64/kvm/mmu.c
> > @@ -1313,7 +1313,7 @@ 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 >=
> > +	if (memslot->base_gfn + memslot->npages >
> >   	    (kvm_phys_size(kvm) >> PAGE_SHIFT))
> >   		return -EFAULT;
> >