Re: [PATCH v2 04/16] xen/riscv: add ioremap_*() variants using ioremap_attr()

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 5/14/25 4:32 PM, Jan Beulich wrote:

> On 06.05.2025 18:51, Oleksii Kurochko wrote:
> > @@ -583,3 +584,36 @@ void *__init arch_vmap_virt_end(void)
> >  {
> >      return (void *)(VMAP_VIRT_START + VMAP_VIRT_SIZE);
> >  }
> > +
> > +static void *ioremap_attr(paddr_t start, size_t len, pte_attr_t attributes)
> > +{
> > +    mfn_t mfn = _mfn(PFN_DOWN(start));
> > +    unsigned int offs = start & (PAGE_SIZE - 1);
> > +    unsigned int nr = PFN_UP(offs + len);
> > +    void *ptr = __vmap(&mfn, nr, 1, 1, attributes, VMAP_DEFAULT);
> > +
> > +    if ( ptr == NULL )
> > +        return NULL;
> > +
> > +    return ptr + offs;
> > +}
> > +
> > +void __iomem *ioremap_nocache(paddr_t start, size_t len)
> > +{
> > +    return ioremap_attr(start, len, PAGE_HYPERVISOR_NOCACHE);
> > +}
> >       
> Why do you need both this and ...
>
> > +void __iomem *ioremap_cache(paddr_t start, size_t len)
> > +{
> > +    return ioremap_attr(start, len, PAGE_HYPERVISOR);
> > +}
> > +
> > +void __iomem *ioremap_wc(paddr_t start, size_t len)
> > +{
> > +    return ioremap_attr(start, len, PAGE_HYPERVISOR_WC);
> > +}
> > +
> > +void *ioremap(paddr_t pa, size_t len)
> > +{
> > +    return ioremap_attr(pa, len, PAGE_HYPERVISOR_NOCACHE);
> > +}
> >       
> ... this? And why's the 1st parameter named differently for this last
> one? Can't they all be in sync in this regard?
>     
Originally, I thought ioremap_nocache() was needed because it is used in
common code. However, I now realize that the calls to ioremap_nocache()
in xen/drivers/char are also ARM-specific. I assume all the
UART drivers currently using ioremap_nocache() are intended for ARM.
I'll drop ioremap_nocache() for RISC-V, and I think it makes sense to
create a separate patch to clean this up for ARM as well.

~ Oleksii