[PATCH v2] efi/unaccepted: Fix off-by-one when checking for overlapping ranges

[PATCH v2] efi/unaccepted: Fix off-by-one when checking for overlapping ranges

[Michael Roth]

When a task needs to accept memory it will scan the accepting_list
to see if any ranges already being processed by other tasks overlap
with its range. Due to an off-by-one in the range comparisons, a task
might falsely determine that an overlapping range is being accepted,
leading to an unnecessary delay before it begins processing the range.

Fix the off-by-one in the range comparison to prevent this and slightly
improve performance.

Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
Link: https://lore.kernel.org/linux-mm/20231101004523.vseyi5bezgfaht5i@amd.com/T/#me2eceb9906fcae5fe958b3fe88e41f920f8335b6
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
v2:
 * Improve commit message terminology (Kirill)
---
 drivers/firmware/efi/unaccepted_memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c
index 135278ddaf62..79fb687bb90f 100644
--- a/drivers/firmware/efi/unaccepted_memory.c
+++ b/drivers/firmware/efi/unaccepted_memory.c
@@ -100,7 +100,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
 	 * overlap on physical address level.
 	 */
 	list_for_each_entry(entry, &accepting_list, list) {
-		if (entry->end < range.start)
+		if (entry->end <= range.start)
 			continue;
 		if (entry->start >= range.end)
 			continue;
-- 
2.25.1

Re: [PATCH v2] efi/unaccepted: Fix off-by-one when checking for overlapping ranges

[Vlastimil Babka]

On 11/3/23 16:13, Michael Roth wrote:
> When a task needs to accept memory it will scan the accepting_list
> to see if any ranges already being processed by other tasks overlap
> with its range. Due to an off-by-one in the range comparisons, a task
> might falsely determine that an overlapping range is being accepted,
> leading to an unnecessary delay before it begins processing the range.
> 
> Fix the off-by-one in the range comparison to prevent this and slightly
> improve performance.
> 
> Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
> Link: https://lore.kernel.org/linux-mm/20231101004523.vseyi5bezgfaht5i@amd.com/T/#me2eceb9906fcae5fe958b3fe88e41f920f8335b6
> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Signed-off-by: Michael Roth <michael.roth@amd.com>

More justification for introducing a common ranges_overlap() helper somewhere :)

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
> v2:
>  * Improve commit message terminology (Kirill)
> ---
>  drivers/firmware/efi/unaccepted_memory.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c
> index 135278ddaf62..79fb687bb90f 100644
> --- a/drivers/firmware/efi/unaccepted_memory.c
> +++ b/drivers/firmware/efi/unaccepted_memory.c
> @@ -100,7 +100,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
>  	 * overlap on physical address level.
>  	 */
>  	list_for_each_entry(entry, &accepting_list, list) {
> -		if (entry->end < range.start)
> +		if (entry->end <= range.start)
>  			continue;
>  		if (entry->start >= range.end)
>  			continue;

Re: [PATCH v2] efi/unaccepted: Fix off-by-one when checking for overlapping ranges

[Ard Biesheuvel]

On Fri, 3 Nov 2023 at 16:30, Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 11/3/23 16:13, Michael Roth wrote:
> > When a task needs to accept memory it will scan the accepting_list
> > to see if any ranges already being processed by other tasks overlap
> > with its range. Due to an off-by-one in the range comparisons, a task
> > might falsely determine that an overlapping range is being accepted,
> > leading to an unnecessary delay before it begins processing the range.
> >
> > Fix the off-by-one in the range comparison to prevent this and slightly
> > improve performance.
> >
> > Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
> > Link: https://lore.kernel.org/linux-mm/20231101004523.vseyi5bezgfaht5i@amd.com/T/#me2eceb9906fcae5fe958b3fe88e41f920f8335b6
> > Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > Signed-off-by: Michael Roth <michael.roth@amd.com>
>
> More justification for introducing a common ranges_overlap() helper somewhere :)
>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
>

Thanks, I'll take this as a fix.


> > ---
> > v2:
> >  * Improve commit message terminology (Kirill)
> > ---
> >  drivers/firmware/efi/unaccepted_memory.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c
> > index 135278ddaf62..79fb687bb90f 100644
> > --- a/drivers/firmware/efi/unaccepted_memory.c
> > +++ b/drivers/firmware/efi/unaccepted_memory.c
> > @@ -100,7 +100,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
> >        * overlap on physical address level.
> >        */
> >       list_for_each_entry(entry, &accepting_list, list) {
> > -             if (entry->end < range.start)
> > +             if (entry->end <= range.start)
> >                       continue;
> >               if (entry->start >= range.end)
> >                       continue;
>

Re: [PATCH v2] efi/unaccepted: Fix off-by-one when checking for overlapping ranges

[Vlastimil Babka]

On 11/8/23 12:21, Ard Biesheuvel wrote:
> On Fri, 3 Nov 2023 at 16:30, Vlastimil Babka <vbabka@suse.cz> wrote:
>>
>> On 11/3/23 16:13, Michael Roth wrote:
>> > When a task needs to accept memory it will scan the accepting_list
>> > to see if any ranges already being processed by other tasks overlap
>> > with its range. Due to an off-by-one in the range comparisons, a task
>> > might falsely determine that an overlapping range is being accepted,
>> > leading to an unnecessary delay before it begins processing the range.
>> >
>> > Fix the off-by-one in the range comparison to prevent this and slightly
>> > improve performance.
>> >
>> > Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
>> > Link: https://lore.kernel.org/linux-mm/20231101004523.vseyi5bezgfaht5i@amd.com/T/#me2eceb9906fcae5fe958b3fe88e41f920f8335b6
>> > Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>> > Signed-off-by: Michael Roth <michael.roth@amd.com>
>>
>> More justification for introducing a common ranges_overlap() helper somewhere :)
>>
>> Acked-by: Vlastimil Babka <vbabka@suse.cz>
>>
> 
> Thanks, I'll take this as a fix.

Ping, can't see it in mainline nor -next?

> 
>> > ---
>> > v2:
>> >  * Improve commit message terminology (Kirill)
>> > ---
>> >  drivers/firmware/efi/unaccepted_memory.c | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c
>> > index 135278ddaf62..79fb687bb90f 100644
>> > --- a/drivers/firmware/efi/unaccepted_memory.c
>> > +++ b/drivers/firmware/efi/unaccepted_memory.c
>> > @@ -100,7 +100,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
>> >        * overlap on physical address level.
>> >        */
>> >       list_for_each_entry(entry, &accepting_list, list) {
>> > -             if (entry->end < range.start)
>> > +             if (entry->end <= range.start)
>> >                       continue;
>> >               if (entry->start >= range.end)
>> >                       continue;
>>
> 

Re: [PATCH v2] efi/unaccepted: Fix off-by-one when checking for overlapping ranges

[Ard Biesheuvel]

On Tue, 28 Nov 2023 at 12:25, Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 11/8/23 12:21, Ard Biesheuvel wrote:
> > On Fri, 3 Nov 2023 at 16:30, Vlastimil Babka <vbabka@suse.cz> wrote:
> >>
> >> On 11/3/23 16:13, Michael Roth wrote:
> >> > When a task needs to accept memory it will scan the accepting_list
> >> > to see if any ranges already being processed by other tasks overlap
> >> > with its range. Due to an off-by-one in the range comparisons, a task
> >> > might falsely determine that an overlapping range is being accepted,
> >> > leading to an unnecessary delay before it begins processing the range.
> >> >
> >> > Fix the off-by-one in the range comparison to prevent this and slightly
> >> > improve performance.
> >> >
> >> > Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
> >> > Link: https://lore.kernel.org/linux-mm/20231101004523.vseyi5bezgfaht5i@amd.com/T/#me2eceb9906fcae5fe958b3fe88e41f920f8335b6
> >> > Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> >> > Signed-off-by: Michael Roth <michael.roth@amd.com>
> >>
> >> More justification for introducing a common ranges_overlap() helper somewhere :)
> >>
> >> Acked-by: Vlastimil Babka <vbabka@suse.cz>
> >>
> >
> > Thanks, I'll take this as a fix.
>
> Ping, can't see it in mainline nor -next?
>

Apologies - queued up now.