Re: [PATCH v2 5/8] xen/riscv: introduce asm/pmap.h header

[Oleksii Kurochko <inisider@gmail.com>]

On Mon, 2024-07-22 at 14:54 +0200, Jan Beulich wrote:
> On 12.07.2024 18:22, Oleksii Kurochko wrote:
> > --- /dev/null
> > +++ b/xen/arch/riscv/include/asm/pmap.h
> > @@ -0,0 +1,28 @@
> > +#ifndef __ASM_PMAP_H__
> > +#define __ASM_PMAP_H__
> > +
> > +#include <xen/bug.h>
> > +#include <xen/mm.h>
> > +
> > +#include <asm/fixmap.h>
> > +
> > +static inline void arch_pmap_map(unsigned int slot, mfn_t mfn)
> > +{
> > +    pte_t *entry = &xen_fixmap[slot];
> > +    pte_t pte;
> > +
> > +    ASSERT(!pte_is_valid(*entry));
> > +
> > +    pte = mfn_to_xen_entry(mfn, PAGE_HYPERVISOR_RW);
> > +    pte.pte |= PTE_LEAF_DEFAULT;
> > +    write_pte(entry, pte);
> > +}
> > +
> > +static inline void arch_pmap_unmap(unsigned int slot)
> > +{
> > +    pte_t pte = {};
> > +
> > +    write_pte(&xen_fixmap[slot], pte);
> > +}
> 
> Why are these not using set_fixmap() / clear_fixmap() respectively?
They haven't been introduced yet. And I thought that these fucntion are
used only in pmap_{un}map() and that is the reason why I decided to not
introduce them. But while writing the answer on another comment, I
found other places where set_fixmap() / clear_fixmap() are used, so I
will introduce them and reuse here.

> 
> > --- a/xen/arch/riscv/mm.c
> > +++ b/xen/arch/riscv/mm.c
> > @@ -370,3 +370,17 @@ int map_pages_to_xen(unsigned long virt,
> >      BUG_ON("unimplemented");
> >      return -1;
> >  }
> > +
> > +static inline pte_t mfn_to_pte(mfn_t mfn)
> 
> This name suggests (to me) that you're getting _the_ (single) PTE for
> a given MFN. However, what the function is doing is make a PTE using
> the given MFN. On x86 at least the common way to name such a function
> would be pte_from_mfn().
If it is a common way then I will rename it. Thanks.

~ Oleksii


> 
> > +{
> > +    unsigned long pte = mfn_x(mfn) << PTE_PPN_SHIFT;
> > +    return (pte_t){ .pte = pte};
> 
> Nit: Blank missing.
> 
> Jan