On 1/20/23 06:56, Al Viro wrote:
On Fri, Jan 20, 2023 at 05:07:48AM +0000, Al Viro wrote:
On Fri, Jan 20, 2023 at 04:54:51AM +0000, Matthew Wilcox wrote:
Sure, but... there's also this:
static inline void __kunmap_local(const void *addr)
{
#ifdef ARCH_HAS_FLUSH_ON_KUNMAP
kunmap_flush_on_unmap(addr);
#endif
}
Are you sure that the guts of that thing will be happy with address that is not
page-aligned? I've looked there at some point, got scared of parisc (IIRC)
MMU details and decided not to rely upon that...
Ugh, PA-RISC (the only implementor) definitely will flush the wrong
addresses. I think we should do this, as having bugs that only manifest
on one not-well-tested architecture seems Bad.
static inline void __kunmap_local(const void *addr)
{
#ifdef ARCH_HAS_FLUSH_ON_KUNMAP
- kunmap_flush_on_unmap(addr);
+ kunmap_flush_on_unmap(PAGE_ALIGN_DOWN(addr));
#endif
}
PTR_ALIGN_DOWN(addr, PAGE_SIZE), perhaps?
Anyway, that's a question to parisc folks; I _think_ pdtlb
quietly ignores the lower bits of address, so that part seems
to be safe, but I wouldn't bet upon that.
No, on PA2.0 (64bit) CPUs the lower bits of the address of pdtlb
encodes the amount of memory (page size) to be flushed, see:
http://ftp.parisc-linux.org/docs/arch/parisc2.0.pdf (page 7-106)
So, the proposed page alignment with e.g. PTR_ALIGN_DON() is needed.
Helge
