Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [PATCH] m68k: mm: Remove check for VM_IO to fix deferred I/O | From | Michael Schmitz <> | Date | Sat, 29 Jan 2022 10:26:01 +1300 |
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Hi Geert,
for hwregs_present(), the exception fixup will handle any access error (through send_fault_sig()), so this should continue to work.
Why the special handling of VM_IO pages? Maybe hp300 had marked all IO register pages VM_IO to distinguish IO faults from VM faults...
The only other area I can imagine this might have an impact is the Mac's pseudo-DMA - FInn might want to give this some testing.
Cheers,
Michael
Am 29.01.2022 um 06:30 schrieb Geert Uytterhoeven: > When an application accesses a mapped frame buffer backed by deferred > I/O, it receives a segmentation fault. Fix this by removing the check > for VM_IO in do_page_fault(). > > Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> > --- > This check was never present in a fault handler on any other > architecture than m68k. > Some digging revealed that it was added in v2.1.106, but I couldn't find > an email with a patch adding it. That same kernel version extended the > use of the hwreg_present() helper to HP9000/300, so the check might have > been needed there, perhaps only during development? > The Atari kernel relies heavily on hwreg_present() (both the success and > failure cases), and these still work, at least on ARAnyM. > --- > arch/m68k/mm/fault.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/arch/m68k/mm/fault.c b/arch/m68k/mm/fault.c > index 1493cf5eac1e7a39..71aa9f6315dc8028 100644 > --- a/arch/m68k/mm/fault.c > +++ b/arch/m68k/mm/fault.c > @@ -93,8 +93,6 @@ int do_page_fault(struct pt_regs *regs, unsigned long address, > vma = find_vma(mm, address); > if (!vma) > goto map_err; > - if (vma->vm_flags & VM_IO) > - goto acc_err; > if (vma->vm_start <= address) > goto good_area; > if (!(vma->vm_flags & VM_GROWSDOWN)) >
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