On Wed, Sep 09, 2020 at 04:29:26PM +0100, Alexandru Elisei wrote:
> On 9/7/20 4:23 PM, Will Deacon wrote:
> > [..]
> > +
> > +int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
> > + struct kvm_pgtable_walker *walker)
> > +{
> > + struct kvm_pgtable_walk_data walk_data = {
> > + .pgt = pgt,
> > + .addr = ALIGN_DOWN(addr, PAGE_SIZE),
> > + .end = PAGE_ALIGN(walk_data.addr + size),
> > + .walker = walker,
> > + };
>
> If the caller wants to walk [0x500, 0x1500), for PAGE_SIZE = 0x1000 (4K), the
> function walks the range [0x0, 0x1000). Is that intentional?
Yes, although the caller specifies a base and a *size*, rather than an end
address. As a concrete example, much of the hypervisor stage-1 mapping
is created using PAGE_SIZE mappings of random ELF symbols, which correspond
to arbitrary addresses. In these cases, we really do want to round-down the
address and perform a PAGE_SIZE mapping.
The alternative would be to return an error if the size is not page-aligned,
but I don't think that's really necessary, especially since we accept an
unaligned base.
Will
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