On 01/20/23 at 10:04am, Simon Horman wrote:
> On Tue, Jan 17, 2023 at 11:49:20AM +0800, Baoquan He wrote:
> > On arm64, reservation for 'crashkernel=xM,high' is taken by searching for
> > suitable memory region up down. If the 'xM' of crashkernel high memory
> > is reserved from high memory successfully, it will try to reserve
> > crashkernel low memory later accoringly. Otherwise, it will try to search
> > low memory area for the 'xM' suitable region.
> >
> > While we observed an unexpected case where a reserved region crosses the
> > high and low meomry boundary. E.g on a system with 4G as low memory end,
> > user added the kernel parameters like: 'crashkernel=512M,high', it could
> > finally have [4G-126M, 4G+386M], [1G, 1G+128M] regions in running kernel.
> > This looks very strange because we have two low memory regions
> > [4G-126M, 4G] and [1G, 1G+128M]. Much explanation need be given to tell
> > why that happened.
> >
> > Here, for crashkernel=xM,high, search the high memory for the suitable
> > region above the high and low memory boundary. If failed, try reserving
> > the suitable region below the boundary. Like this, the crashkernel high
> > region will only exist in high memory, and crashkernel low region only
> > exists in low memory. The reservation behaviour for crashkernel=,high is
> > clearer and simpler.
> >
> > Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
> > ---
> > arch/arm64/mm/init.c | 30 +++++++++++++++++++++++-------
> > 1 file changed, 23 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index 58a0bb2c17f1..26a05af2bfa8 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -127,12 +127,13 @@ static int __init reserve_crashkernel_low(unsigned long long low_size)
> > */
> > static void __init reserve_crashkernel(void)
> > {
> > - unsigned long long crash_base, crash_size;
> > - unsigned long long crash_low_size = 0;
> > + unsigned long long crash_base, crash_size, search_base;
> > unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
> > + unsigned long long crash_low_size = 0;
> > char *cmdline = boot_command_line;
> > - int ret;
> > bool fixed_base = false;
> > + bool high = false;
> > + int ret;
> >
> > if (!IS_ENABLED(CONFIG_KEXEC_CORE))
> > return;
> > @@ -155,7 +156,9 @@ static void __init reserve_crashkernel(void)
> > else if (ret)
> > return;
> >
> > + search_base = CRASH_ADDR_LOW_MAX;
> > crash_max = CRASH_ADDR_HIGH_MAX;
> > + high = true;
> > } else if (ret || !crash_size) {
> > /* The specified value is invalid */
> > return;
> > @@ -166,31 +169,44 @@ static void __init reserve_crashkernel(void)
> > /* User specifies base address explicitly. */
> > if (crash_base) {
> > fixed_base = true;
> > + search_base = crash_base;
> > crash_max = crash_base + crash_size;
> > }
> >
> > retry:
> > crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
> > - crash_base, crash_max);
> > + search_base, crash_max);
> > if (!crash_base) {
> > + if (fixed_base) {
> > + pr_warn("cannot reserve crashkernel region [0x%llx-0x%llx]\n",
> > + search_base, crash_max);
> > + return;
> > + }
> > +
> > /*
> > * If the first attempt was for low memory, fall back to
> > * high memory, the minimum required low memory will be
> > * reserved later.
> > */
> > - if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) {
> > + if (!high && crash_max == CRASH_ADDR_LOW_MAX) {
> > crash_max = CRASH_ADDR_HIGH_MAX;
> > + search_base = CRASH_ADDR_LOW_MAX;
> > crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> > goto retry;
> > }
> >
> > + if (high && (crash_max == CRASH_ADDR_HIGH_MAX)) {
>
> nit: unnecessary (and inconsistent with code just above) parentheses.
Indeed, will remove it. Thanks for reviewing.
>
> > + crash_max = CRASH_ADDR_LOW_MAX;
> > + search_base = 0;
> > + goto retry;
> > + }
> > pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
> > crash_size);
> > return;
> > }
> >
> > - if ((crash_base > CRASH_ADDR_LOW_MAX - crash_low_size) &&
> > - crash_low_size && reserve_crashkernel_low(crash_low_size)) {
> > + if ((crash_base >= CRASH_ADDR_LOW_MAX) && crash_low_size &&
> > + reserve_crashkernel_low(crash_low_size)) {
> > memblock_phys_free(crash_base, crash_size);
> > return;
> > }
> > --
> > 2.34.1
> >
> >
> > _______________________________________________
> > kexec mailing list
> > kexec@xxxxxxxxxxxxxxxxxxx
> > http://lists.infradead.org/mailman/listinfo/kexec
> >
>
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