On Mon, Apr 12, 2021 at 5:52 PM Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxx> wrote:
>
> During the EEH MMIO error checking, the current implementation fails to map
> the (virtual) MMIO address back to the pci device on radix with hugepage
> mappings for I/O. This results into failure to dispatch EEH event with no
> recovery even when EEH capability has been enabled on the device.
>
> eeh_check_failure(token) # token = virtual MMIO address
> addr = eeh_token_to_phys(token);
> edev = eeh_addr_cache_get_dev(addr);
> if (!edev)
> return 0;
> eeh_dev_check_failure(edev); <= Dispatch the EEH event
>
> In case of hugepage mappings, eeh_token_to_phys() has a bug in virt -> phys
> translation that results in wrong physical address, which is then passed to
> eeh_addr_cache_get_dev() to match it against cached pci I/O address ranges
> to get to a PCI device. Hence, it fails to find a match and the EEH event
> never gets dispatched leaving the device in failed state.
>
> The commit 33439620680be ("powerpc/eeh: Handle hugepages in ioremap space")
> introduced following logic to translate virt to phys for hugepage mappings:
>
> eeh_token_to_phys():
> + pa = pte_pfn(*ptep);
> +
> + /* On radix we can do hugepage mappings for io, so handle that */
> + if (hugepage_shift) {
> + pa <<= hugepage_shift; <= This is wrong
> + pa |= token & ((1ul << hugepage_shift) - 1);
> + }
I think I vaguely remember thinking "is this right?" at the time.
Apparently not!
Reviewed-by: Oliver O'Halloran <oohall@xxxxxxxxx>
It would probably be a good idea to add a debugfs interface to help
with testing the address translation. Maybe something like:
echo <mmio addr> > /sys/kernel/debug/powerpc/eeh_addr_check
Then in the kernel:
struct resource *r = lookup_resource(mmio_addr);
void *virt = ioremap_resource(r);
ret = eeh_check_failure(virt);
iounmap(virt)
return ret;
A little tedious, but then you can write a selftest :)
Oliver
