| Message ID | 20220112193340.149020-3-hbathini@linux.ibm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | powerpc/fadump: handle CMA activation failure appropriately | expand |
On 12.01.22 20:33, Hari Bathini wrote: > With commit a4e92ce8e4c8 ("powerpc/fadump: Reservationless firmware > assisted dump"), Linux kernel's Contiguous Memory Allocator (CMA) > based reservation was introduced in fadump. That change was aimed at > using CMA to let applications utilize the memory reserved for fadump > while blocking it from being used for kernel pages. The assumption > was, even if CMA activation fails for whatever reason, the memory > still remains reserved to avoid it from being used for kernel pages. > But commit 072355c1cf2d ("mm/cma: expose all pages to the buddy if > activation of an area fails") breaks this assumption as it started > exposing all pages to buddy allocator on CMA activation failure. > It led to warning messages like below while running crash-utility > on vmcore of a kernel having above two commits: > > crash: seek error: kernel virtual address: <from reserved region> > > To fix this problem, opt out from exposing pages to buddy allocator > on CMA activation failure for fadump reserved memory. > > Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> > --- > arch/powerpc/kernel/fadump.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c > index b7ceb041743c..82058b52e34a 100644 > --- a/arch/powerpc/kernel/fadump.c > +++ b/arch/powerpc/kernel/fadump.c > @@ -112,6 +112,12 @@ static int __init fadump_cma_init(void) > return 1; > } > > + /* > + * If CMA activation fails, keep the pages reserved, instead of > + * exposing them to buddy allocator. Same as 'fadump=nocma' case. > + */ > + cma_reserve_pages_on_error(fadump_cma); > + > /* > * So we now have successfully initialized cma area for fadump. > */ Acked-by: David Hildenbrand <david@redhat.com>
diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c index b7ceb041743c..82058b52e34a 100644 --- a/arch/powerpc/kernel/fadump.c +++ b/arch/powerpc/kernel/fadump.c @@ -112,6 +112,12 @@ static int __init fadump_cma_init(void) return 1; } + /* + * If CMA activation fails, keep the pages reserved, instead of + * exposing them to buddy allocator. Same as 'fadump=nocma' case. + */ + cma_reserve_pages_on_error(fadump_cma); + /* * So we now have successfully initialized cma area for fadump. */
With commit a4e92ce8e4c8 ("powerpc/fadump: Reservationless firmware assisted dump"), Linux kernel's Contiguous Memory Allocator (CMA) based reservation was introduced in fadump. That change was aimed at using CMA to let applications utilize the memory reserved for fadump while blocking it from being used for kernel pages. The assumption was, even if CMA activation fails for whatever reason, the memory still remains reserved to avoid it from being used for kernel pages. But commit 072355c1cf2d ("mm/cma: expose all pages to the buddy if activation of an area fails") breaks this assumption as it started exposing all pages to buddy allocator on CMA activation failure. It led to warning messages like below while running crash-utility on vmcore of a kernel having above two commits: crash: seek error: kernel virtual address: <from reserved region> To fix this problem, opt out from exposing pages to buddy allocator on CMA activation failure for fadump reserved memory. Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> --- arch/powerpc/kernel/fadump.c | 6 ++++++ 1 file changed, 6 insertions(+)