On 05/27/23 at 08:34pm, Zhen Lei wrote: > The crashk_low_res should be considered by /sys/kernel/kexec_crash_size > to support two crash kernel regions. Since crashk_res manages the memory > with high address and crashk_low_res manages the memory with low address, > crashk_low_res is shrunken only when all crashk_res is shrunken. And > because when there is only one crash kernel region, crashk_res is always > used. Therefore, if all crashk_res is shrunken and crashk_low_res still > exists, swap them.
This looks good, otherwise someone else won't stop attempting to add support of crashk_low_res shrinking. Not sure if this will bring corner case issue in testing, let's see. For the patch log, I tried to rephrase, feel free to refer to. ===== The crashk_low_res should be considered by /sys/kernel/kexec_crash_size to support two crash kernel regions shrinking if existing. While doing it, crashk_low_res will only be shrunk when the entire crashk_res is empty; and if the crashk_res is empty and crahk_low_res is not, change crashk_low_res to be crashk_res. ===== With the log updated, you can add: Acked-by: Baoquan He <[email protected]> > > Signed-off-by: Zhen Lei <[email protected]> > --- > kernel/kexec_core.c | 43 ++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 38 insertions(+), 5 deletions(-) > > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c > index e82bc6d6634136a..c1d50f6566300d9 100644 > --- a/kernel/kexec_core.c > +++ b/kernel/kexec_core.c > @@ -1091,6 +1091,11 @@ __bpf_kfunc void crash_kexec(struct pt_regs *regs) > } > } > > +static inline resource_size_t crash_resource_size(const struct resource *res) > +{ > + return !res->end ? 0 : resource_size(res); > +} > + > ssize_t crash_get_memory_size(void) > { > ssize_t size = 0; > @@ -1098,8 +1103,8 @@ ssize_t crash_get_memory_size(void) > if (!kexec_trylock()) > return -EBUSY; > > - if (crashk_res.end != crashk_res.start) > - size = resource_size(&crashk_res); > + size += crash_resource_size(&crashk_res); > + size += crash_resource_size(&crashk_low_res); > > kexec_unlock(); > return size; > @@ -1135,7 +1140,7 @@ int __crash_shrink_memory(struct resource *old_res, > unsigned long new_size) > int crash_shrink_memory(unsigned long new_size) > { > int ret = 0; > - unsigned long old_size; > + unsigned long old_size, low_size; > > if (!kexec_trylock()) > return -EBUSY; > @@ -1144,14 +1149,42 @@ int crash_shrink_memory(unsigned long new_size) > ret = -ENOENT; > goto unlock; > } > - old_size = !crashk_res.end ? 0 : resource_size(&crashk_res); > + > + low_size = crash_resource_size(&crashk_low_res); > + old_size = crash_resource_size(&crashk_res) + low_size; > new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN); > if (new_size >= old_size) { > ret = (new_size == old_size) ? 0 : -EINVAL; > goto unlock; > } > > - ret = __crash_shrink_memory(&crashk_res, new_size); > + /* > + * (low_size > new_size) implies that low_size is greater than zero. > + * This also means that if low_size is zero, the else branch is taken. > + * > + * If low_size is greater than 0, (low_size > new_size) indicates that > + * crashk_low_res also needs to be shrunken. Otherwise, only crashk_res > + * needs to be shrunken. > + */ > + if (low_size > new_size) { > + ret = __crash_shrink_memory(&crashk_res, 0); > + if (ret) > + goto unlock; > + > + ret = __crash_shrink_memory(&crashk_low_res, new_size); > + } else { > + ret = __crash_shrink_memory(&crashk_res, new_size - low_size); > + } > + > + /* Swap crashk_res and crashk_low_res if needed */ > + if (!crashk_res.end && crashk_low_res.end) { > + crashk_res.start = crashk_low_res.start; > + crashk_res.end = crashk_low_res.end; > + release_resource(&crashk_low_res); > + crashk_low_res.start = 0; > + crashk_low_res.end = 0; > + insert_resource(&iomem_resource, &crashk_res); > + } > > unlock: > kexec_unlock(); > -- > 2.25.1 > _______________________________________________ kexec mailing list [email protected] http://lists.infradead.org/mailman/listinfo/kexec
