Hi Nick,
Nicholas Piggin <npiggin@xxxxxxxxx> writes:
> Santosh Sivaraj's on August 15, 2019 10:39 am:
>> From: Balbir Singh <bsingharora@xxxxxxxxx>
>>
>> The current code would fail on huge pages addresses, since the shift would
>> be incorrect. Use the correct page shift value returned by
>> __find_linux_pte() to get the correct physical address. The code is more
>> generic and can handle both regular and compound pages.
>>
>> Fixes: ba41e1e1ccb9 ("powerpc/mce: Hookup derror (load/store) UE errors")
>> Signed-off-by: Balbir Singh <bsingharora@xxxxxxxxx>
>> [arbab@xxxxxxxxxxxxx: Fixup pseries_do_memory_failure()]
>> Signed-off-by: Reza Arbab <arbab@xxxxxxxxxxxxx>
>> Co-developed-by: Santosh Sivaraj <santosh@xxxxxxxxxx>
>> Signed-off-by: Santosh Sivaraj <santosh@xxxxxxxxxx>
>> Tested-by: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx>
>> Cc: stable@xxxxxxxxxxxxxxx # v4.15+
>> ---
>> arch/powerpc/include/asm/mce.h | 2 +-
>> arch/powerpc/kernel/mce_power.c | 55 ++++++++++++++--------------
>> arch/powerpc/platforms/pseries/ras.c | 9 ++---
>> 3 files changed, 32 insertions(+), 34 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
>> index a4c6a74ad2fb..f3a6036b6bc0 100644
>> --- a/arch/powerpc/include/asm/mce.h
>> +++ b/arch/powerpc/include/asm/mce.h
>> @@ -209,7 +209,7 @@ extern void release_mce_event(void);
>> extern void machine_check_queue_event(void);
>> extern void machine_check_print_event_info(struct machine_check_event *evt,
>> bool user_mode, bool in_guest);
>> -unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr);
>> +unsigned long addr_to_phys(struct pt_regs *regs, unsigned long addr);
>> #ifdef CONFIG_PPC_BOOK3S_64
>> void flush_and_reload_slb(void);
>> #endif /* CONFIG_PPC_BOOK3S_64 */
>> diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
>> index a814d2dfb5b0..e74816f045f8 100644
>> --- a/arch/powerpc/kernel/mce_power.c
>> +++ b/arch/powerpc/kernel/mce_power.c
>> @@ -20,13 +20,14 @@
>> #include <asm/exception-64s.h>
>>
>> /*
>> - * Convert an address related to an mm to a PFN. NOTE: we are in real
>> - * mode, we could potentially race with page table updates.
>> + * Convert an address related to an mm to a physical address.
>> + * NOTE: we are in real mode, we could potentially race with page table updates.
>> */
>> -unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)
>> +unsigned long addr_to_phys(struct pt_regs *regs, unsigned long addr)
>> {
>> - pte_t *ptep;
>> - unsigned long flags;
>> + pte_t *ptep, pte;
>> + unsigned int shift;
>> + unsigned long flags, phys_addr;
>> struct mm_struct *mm;
>>
>> if (user_mode(regs))
>> @@ -35,14 +36,21 @@ unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)
>> mm = &init_mm;
>>
>> local_irq_save(flags);
>> - if (mm == current->mm)
>> - ptep = find_current_mm_pte(mm->pgd, addr, NULL, NULL);
>> - else
>> - ptep = find_init_mm_pte(addr, NULL);
>> + ptep = __find_linux_pte(mm->pgd, addr, NULL, &shift);
>> local_irq_restore(flags);
>> +
>> if (!ptep || pte_special(*ptep))
>> return ULONG_MAX;
>> - return pte_pfn(*ptep);
>> +
>> + pte = *ptep;
>> + if (shift > PAGE_SHIFT) {
>> + unsigned long rpnmask = (1ul << shift) - PAGE_SIZE;
>> +
>> + pte = __pte(pte_val(pte) | (addr & rpnmask));
>> + }
>> + phys_addr = pte_pfn(pte) << PAGE_SHIFT;
>> +
>> + return phys_addr;
>> }
>
> This should remain addr_to_pfn I think. None of the callers care what
> size page the EA was mapped with. 'pfn' is referring to the Linux pfn,
> which is the small page number.
>
> if (shift > PAGE_SHIFT)
> return (pte_pfn(*ptep) | ((addr & ((1UL << shift) - 1)) >> PAGE_SHIFT);
> else
> return pte_pfn(*ptep);
>
> Something roughly like that, then you don't have to change any callers
> or am I missing something?
Here[1] you asked to return the real address rather than pfn, which all
callers care about. So made the changes accordingly.
[1] https://www.spinics.net/lists/kernel/msg3187658.html
Thanks,
Santosh
>
> Thanks,
> Nick
