| Message ID | 20230524131238.2791-1-jszhang@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: mm: pass original fault address to handle_mm_fault() in PER_VMA_LOCK block | expand |
On Wed, May 24, 2023 at 09:12:38PM +0800, Jisheng Zhang wrote: > When reading the arm64's PER_VMA_LOCK support code, I found a bit > difference between arm64 and other arch when calling handle_mm_fault() > during VMA lock-based page fault handling: the fault address is masked > before passing to handle_mm_fault(). This is also different from the > usage in mmap_lock-based handling. I think we need to pass the > original fault address to handle_mm_fault() as we did in > commit 84c5e23edecd ("arm64: mm: Pass original fault address to > handle_mm_fault()"). > > If we go through the code path further, we can find that the "masked" > fault address can cause mismatched fault address between perf sw > major/minor page fault sw event and perf page fault sw event: OOPS, sorry please ignore this one. I pressed ctrl-c to interrupt the git send-mail, but it's still sent out ;) Instead, let's focus on https://lore.kernel.org/linux-arm-kernel/20230524131305.2808-1-jszhang@kernel.org/T/#u The two patches are the same, I just added Suren into CC list. > > do_page_fault > perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, ..., addr) // orig addr > handle_mm_fault > mm_account_fault > perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, ...) // masked addr > > Fixes: cd7f176aea5f ("arm64/mm: try VMA lock-based page fault handling first") > Signed-off-by: Jisheng Zhang <jszhang@kernel.org> > --- > arch/arm64/mm/fault.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index cb21ccd7940d..6045a5117ac1 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -600,8 +600,7 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > vma_end_read(vma); > goto lock_mmap; > } > - fault = handle_mm_fault(vma, addr & PAGE_MASK, > - mm_flags | FAULT_FLAG_VMA_LOCK, regs); > + fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs); > vma_end_read(vma); > > if (!(fault & VM_FAULT_RETRY)) { > -- > 2.40.1 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Wed, May 24, 2023 at 6:38 AM Jisheng Zhang <jszhang@kernel.org> wrote: > > On Wed, May 24, 2023 at 09:12:38PM +0800, Jisheng Zhang wrote: > > When reading the arm64's PER_VMA_LOCK support code, I found a bit > > difference between arm64 and other arch when calling handle_mm_fault() > > during VMA lock-based page fault handling: the fault address is masked > > before passing to handle_mm_fault(). This is also different from the > > usage in mmap_lock-based handling. I think we need to pass the > > original fault address to handle_mm_fault() as we did in > > commit 84c5e23edecd ("arm64: mm: Pass original fault address to > > handle_mm_fault()"). Thanks for noticing. I'm not sure why this masking leaked into my patch. I don't think I wrote it before 84c5e23edecd was merged in June 2021. Anyway, your assessment looks correct to me. > > > > If we go through the code path further, we can find that the "masked" > > fault address can cause mismatched fault address between perf sw > > major/minor page fault sw event and perf page fault sw event: > > OOPS, sorry please ignore this one. I pressed ctrl-c to interrupt the > git send-mail, but it's still sent out ;) > > Instead, let's focus on > https://lore.kernel.org/linux-arm-kernel/20230524131305.2808-1-jszhang@kernel.org/T/#u > > The two patches are the same, I just added Suren into CC list. > > > > > do_page_fault > > perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, ..., addr) // orig addr > > handle_mm_fault > > mm_account_fault > > perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, ...) // masked addr > > > > Fixes: cd7f176aea5f ("arm64/mm: try VMA lock-based page fault handling first") > > Signed-off-by: Jisheng Zhang <jszhang@kernel.org> Reviewed-by: Suren Baghdasaryan <surenb@google.com> > > --- > > arch/arm64/mm/fault.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > > index cb21ccd7940d..6045a5117ac1 100644 > > --- a/arch/arm64/mm/fault.c > > +++ b/arch/arm64/mm/fault.c > > @@ -600,8 +600,7 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > > vma_end_read(vma); > > goto lock_mmap; > > } > > - fault = handle_mm_fault(vma, addr & PAGE_MASK, > > - mm_flags | FAULT_FLAG_VMA_LOCK, regs); > > + fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs); > > vma_end_read(vma); > > > > if (!(fault & VM_FAULT_RETRY)) { > > -- > > 2.40.1 > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On 5/24/23 18:42, Jisheng Zhang wrote: > When reading the arm64's PER_VMA_LOCK support code, I found a bit > difference between arm64 and other arch when calling handle_mm_fault() > during VMA lock-based page fault handling: the fault address is masked > before passing to handle_mm_fault(). This is also different from the > usage in mmap_lock-based handling. I think we need to pass the > original fault address to handle_mm_fault() as we did in > commit 84c5e23edecd ("arm64: mm: Pass original fault address to > handle_mm_fault()"). > > If we go through the code path further, we can find that the "masked" > fault address can cause mismatched fault address between perf sw > major/minor page fault sw event and perf page fault sw event: > > do_page_fault > perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, ..., addr) // orig addr > handle_mm_fault > mm_account_fault > perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, ...) // masked addr > > Fixes: cd7f176aea5f ("arm64/mm: try VMA lock-based page fault handling first") > Signed-off-by: Jisheng Zhang <jszhang@kernel.org> LGTM Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > arch/arm64/mm/fault.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index cb21ccd7940d..6045a5117ac1 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -600,8 +600,7 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > vma_end_read(vma); > goto lock_mmap; > } > - fault = handle_mm_fault(vma, addr & PAGE_MASK, > - mm_flags | FAULT_FLAG_VMA_LOCK, regs); > + fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs); > vma_end_read(vma); > > if (!(fault & VM_FAULT_RETRY)) {
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index cb21ccd7940d..6045a5117ac1 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -600,8 +600,7 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, vma_end_read(vma); goto lock_mmap; } - fault = handle_mm_fault(vma, addr & PAGE_MASK, - mm_flags | FAULT_FLAG_VMA_LOCK, regs); + fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs); vma_end_read(vma); if (!(fault & VM_FAULT_RETRY)) {
When reading the arm64's PER_VMA_LOCK support code, I found a bit difference between arm64 and other arch when calling handle_mm_fault() during VMA lock-based page fault handling: the fault address is masked before passing to handle_mm_fault(). This is also different from the usage in mmap_lock-based handling. I think we need to pass the original fault address to handle_mm_fault() as we did in commit 84c5e23edecd ("arm64: mm: Pass original fault address to handle_mm_fault()"). If we go through the code path further, we can find that the "masked" fault address can cause mismatched fault address between perf sw major/minor page fault sw event and perf page fault sw event: do_page_fault perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, ..., addr) // orig addr handle_mm_fault mm_account_fault perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, ...) // masked addr Fixes: cd7f176aea5f ("arm64/mm: try VMA lock-based page fault handling first") Signed-off-by: Jisheng Zhang <jszhang@kernel.org> --- arch/arm64/mm/fault.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)