On Tue, Jul 19, 2016 at 02:27:54PM +0100, Mark Rutland wrote: > On Tue, Jul 19, 2016 at 08:48:57AM -0400, Mark Salter wrote: > > On Tue, 2016-07-19 at 18:41 +0800, Dennis Chen wrote: > > > On Tue, Jul 19, 2016 at 07:28:16PM +0900, AKASHI Takahiro wrote: > > > > On Tue, Jul 19, 2016 at 05:39:07PM +0800, Dennis Chen wrote: > > > > > On Tue, Jul 12, 2016 at 02:05:07PM +0900, AKASHI Takahiro wrote: > > > > > > +/* > > > > > > + * reserve_crashkernel() - reserves memory for crash kernel > > > > > > + * > > > > > > + * This function reserves memory area given in "crashkernel=" kernel command > > > > > > + * line parameter. The memory reserved is used by dump capture kernel when > > > > > > + * primary kernel is crashing. > > > > > > + */ > > > > > > +static void __init reserve_crashkernel(void) > > > > > > +{ > > > > > > +?????int ret; > > > > > > + > > > > > > +?????ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(), > > > > > > +?????????????????????????????&crash_size, &crash_base); > > > > > > +?????/* no crashkernel= or invalid value specified */ > > > > > > +?????if (ret || !crash_size) > > > > > > +?????????????return; > > > > > > + > > > > > > +?????if (crash_base == 0) { > > > > > > +?????????????/* Current arm64 boot protocol requires 2MB alignment */ > > > > > > +?????????????crash_base = memblock_find_in_range(0, > > > > > > +?????????????????????????????MEMBLOCK_ALLOC_ACCESSIBLE, crash_size, SZ_2M); > > > > > > +?????????????if (crash_base == 0) { > > > > > > +?????????????????????pr_warn("Unable to allocate crashkernel (size:%llx)\n", > > > > > > +?????????????????????????????crash_size); > > > > > > +?????????????????????return; > > > > > > +?????????????} > > > > > > +?????????????memblock_reserve(crash_base, crash_size); > > > > > > > > > > > I am not pretty sure the context here, but > > > > > can we use below code piece instead of the above lines? > > > > > ????????if (crash_base == 0) > > > > > ????????????????memblock_alloc(crash_size, SZ_2M); > > > > Either would be fine here. > > > > > > > Hello AKASHI, maybe you can succeed to find the base with memblock_find_in_range(),? > > > but that doesn't mean you will also succeed to reserve them with memblock_reserve followed. > > > > We avoid memblock_alloc() here because it panics on failure. This could happen > > if user asks for an unusually large crashkernel size. Better to print a message > > and keep booting. Checking the return value of memblock_reserve() seems like a > > good thing to do though. > > Another option would be to add a memblock_try_alloc() function to the > memblock API, which in case of failure returns 0 rather than triggering > a panic(). We'd still have to check the return value, but all the > memblock manipulation would be in one place. > > It looks like adding that is fairly simple: > > phys_addr_t __init memblock_try_alloc(phys_addr_t size, phys_addr_t align) > { > return __memblock_alloc_base(size, align, MEMBLOCK_ALLOC_ACCESSIBLE); > } > Hi Mark, memblock_alloc() should remove the panic just as we did in kmalloc IMO, as a memory allocation API, it should handover the failure case to the user and the latter should make the final decision. Just take a look at the usage case of the memblock_alloc() in the kernel tree, codes have been messed up by -- some codes check the return value of memblock_alloc, while others not. Thanks, Dennis > > Thanks, > Mark. >