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Re: [PATCH v1 3/9] parisc: Convert DMA map_page to map_phys interface
- To: John David Anglin <dave.anglin@xxxxxxxx>
- From: Jason Gunthorpe <jgg@xxxxxxxxxx>
- Date: Fri, 3 Oct 2025 14:26:18 -0300
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- Delivery-date: Fri, 03 Oct 2025 17:26:49 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Fri, Oct 03, 2025 at 01:18:32PM -0400, John David Anglin wrote:
> On 2025-10-03 11:01 a.m., Jason Gunthorpe wrote:
> > This doesn't actually use the virt at all:
> >
> > offset = ((unsigned long) addr) & ~IOVP_MASK;
> > if((size % L1_CACHE_BYTES) || ((unsigned long)addr % L1_CACHE_BYTES))
> > ccio_io_pdir_entry(pdir_start, KERNEL_SPACE, (unsigned
> > long)addr, hint);
> >
> > And ccio_io_pdir_entry():
> > pa = lpa(vba);
> >
> > Is a special instruction that uses virt but AI tells me that special
> > LPA instruction is returning phys. Not sure if that is a different
> > value than virt_to_phys()..
>
> ccio_io_pdir_entry currently only supports KERNEL_SPACE. For KERNEL_SPACE,
> lpa() and
> virt_to_phys() are equivalent if page is mapped. lpa() returns 0 if a
> non-access data
> TLB fault occurs (i.e., page isn't mapped). Not sure if that
> matters.
After unfolding everything the expression is
lpa(phys_to_virt(pa))
So if that is always equal to pa then lets just drop it.
phys_to_virt() always returns something kernel mapped, and it can't be
unmapped.
Jason
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