Re: [PATCH v2] KVM: arm64: Remove size-order align in the nVHE hyp private VA range

[Vincent Donnefort <vdonnefort@google.com>]

[...]

> > +int create_hyp_stack(phys_addr_t phys_addr, unsigned long *haddr)
> > +{
> > +       unsigned long base;
> > +       size_t size;
> > +       int ret;
> > +
> > +       mutex_lock(&kvm_hyp_pgd_mutex);
> > +       /*
> > +        * Efficient stack verification using the PAGE_SHIFT bit implies
> > +        * an alignment of our allocation on the order of the size.
> > +        */
> > +       size = PAGE_SIZE * 2;
> > +       base = ALIGN_DOWN(io_map_base - size, size);
> > +
> > +       ret = __hyp_alloc_private_va_range(base);
> > +
> > +       mutex_unlock(&kvm_hyp_pgd_mutex);
> > +
> > +       if (ret) {
> > +               kvm_err("Cannot allocate hyp stack guard page\n");
> > +               return ret;
> > +       }
> > +
> > +       /*
> > +        * Since the stack grows downwards, map the stack to the page
> > +        * at the higher address and leave the lower guard page
> > +        * unbacked.
> > +        *
> > +        * Any valid stack address now has the PAGE_SHIFT bit as 1
> > +        * and addresses corresponding to the guard page have the
> > +        * PAGE_SHIFT bit as 0 - this is used for overflow detection.
> > +        */
> > +       ret = __create_hyp_mappings(base + PAGE_SIZE, PAGE_SIZE, phys_addr,
> > +                                   PAGE_HYP);
> > +       if (ret)
> > +               kvm_err("Cannot map hyp stack\n");
> 
> Should we reset the io_map_base if the mapping failed here as well?

I didn't do it on purpose. Here, I'm releasing the lock and I didn't want to add
a non locked __create_hyp_mappings() just for that reset that is probably not
binging much.

> 
> Otherwise lgtm, Reviewed-by: Kalesh Singh <kaleshsingh@google.com>

Thanks for the review!

> 
> Thanks,
> Kalesh
> 
> > +
> > +       *haddr = base + size;
> > +
> > +       return ret;
> > +}
> > +
> >  /**
> >   * create_hyp_io_mappings - Map IO into both kernel and HYP
> >   * @phys_addr: The physical start address which gets mapped
> >
> > base-commit: 52a93d39b17dc7eb98b6aa3edb93943248e03b2f
> > --
> > 2.41.0.640.ga95def55d0-goog
> >