----- Original Message ----- > Hi Kazu, > > On 02/20/2019 02:17 AM, Kazuhito Hagio wrote: > > Hi Bhupesh, > > > > -----Original Message----- > >> I am not sure you got a chance to look at the two regression cases I > >> reported here: > >> <http://lists.infradead.org/pipermail/kexec/2019-February/022449.html> > >> > >> Unfortunately the above suggestion doesn't provide any fix for > >> ARMv8.2-LPA regression (see text under heading ' > >> (1). Regression Case 1 (ARMv8.2-LPA enabled kernel)') > > > > As for MAX_PHYSMEM_BITS, I realized that ppc64 makedumpfile can detect > > it because there is only one SECTION_SIZE_BITS for ppc64. I think we > > can use the same way as set_ppc64_max_physmem_bits() does also for > > arm64 for now. I'm going to write it for kernels not having > > NUMBER(MAX_PHYSMEM_BITS) in vmcoreinfo. > > I see two drawbacks with the above approach: > > a). This means that other user-space tools like crash-utility would > still be broken and would probably need to find MAX_PHYSMEM_BITS for > arm64 via a similar (hack'ish ?) approach. > > b). I am looking at the makedumpfile code for 'MAX_PHYSMEM_BITS' > determination for two archs as an example: > > ppc > --- > > int > set_ppc64_max_physmem_bits(void) > { > long array_len = ARRAY_LENGTH(mem_section); > /* > * The older ppc64 kernels uses _MAX_PHYSMEM_BITS as 42 and the > * newer kernels 3.7 onwards uses 46 bits. > */ > > info->max_physmem_bits = _MAX_PHYSMEM_BITS_ORIG ; > if ((array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT_EXTREME())) > || (array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT()))) > return TRUE; > > info->max_physmem_bits = _MAX_PHYSMEM_BITS_3_7; > if ((array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT_EXTREME())) > || (array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT()))) > return TRUE; > > info->max_physmem_bits = _MAX_PHYSMEM_BITS_4_19; > if ((array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT_EXTREME())) > || (array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT()))) > return TRUE; > > info->max_physmem_bits = _MAX_PHYSMEM_BITS_4_20; > if ((array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT_EXTREME())) > || (array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT()))) > return TRUE; > > return FALSE; > } > > x86_64: > ------ > > int > get_versiondep_info_x86_64(void) > { > /* > * On linux-2.6.26, MAX_PHYSMEM_BITS is changed to 44 from 40. > */ > if (info->kernel_version < KERNEL_VERSION(2, 6, 26)) > info->max_physmem_bits = _MAX_PHYSMEM_BITS_ORIG; > else if (info->kernel_version < KERNEL_VERSION(2, 6, 31)) > info->max_physmem_bits = _MAX_PHYSMEM_BITS_2_6_26; > else if(check_5level_paging()) > info->max_physmem_bits = _MAX_PHYSMEM_BITS_5LEVEL; > else > info->max_physmem_bits = _MAX_PHYSMEM_BITS_2_6_31; > > ... > } > > Looking at the above, two questions come to my mind: > > - Do we really need all the above complexity in user-space code, to hoop > across various kernel versions and perform allocations for something > that can be so easily exported via vmcoreinfo? Also we need to see how > portable is the above code for a new kernel version - IMO, it will need > another fix patch when we update to a new kernel version in near future. I agree -- not to mention that the "kernel version" way of determining things does not account for distribution-specific backports. > > - Also do we need to replicate the above implementations across > user-space tools when they can also utilize the vmcoreinfo information > to determine the PA_BITS range without any additional arch/kernel > version specific details as the single point of obtaining this > information from the kernel? > > So, in view of the above, I would still advocate that we use a > vmcoreinfo export for 'MAX_PHYSMEM_BITS' as well to have a uniform > interface for the same across all user-land applications. Again, totally agree. Dave > Thanks, > Bhupesh > > _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
