[PATCH 06/15] arm64: Add KHO support
Alexander Graf
graf at amazon.com
Mon Dec 18 15:01:02 PST 2023
Hey Rob!
On 14.12.23 23:36, Rob Herring wrote:
> On Wed, Dec 13, 2023 at 12:04:43AM +0000, Alexander Graf wrote:
>> We now have all bits in place to support KHO kexecs. This patch adds
>> awareness of KHO in the kexec file as well as boot path for arm64 and
>> adds the respective kconfig option to the architecture so that it can
>> use KHO successfully.
>>
>> Signed-off-by: Alexander Graf <graf at amazon.com>
>> ---
>> arch/arm64/Kconfig | 12 ++++++++++++
>> arch/arm64/kernel/setup.c | 2 ++
>> arch/arm64/mm/init.c | 8 ++++++++
>> drivers/of/fdt.c | 41 +++++++++++++++++++++++++++++++++++++++
>> drivers/of/kexec.c | 36 ++++++++++++++++++++++++++++++++++
>> 5 files changed, 99 insertions(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 7b071a00425d..1ba338ce7598 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -1501,6 +1501,18 @@ config ARCH_SUPPORTS_CRASH_DUMP
>> config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
>> def_bool CRASH_CORE
>>
>> +config KEXEC_KHO
>> + bool "kexec handover"
>> + depends on KEXEC
>> + select MEMBLOCK_SCRATCH
>> + select LIBFDT
>> + select CMA
>> + help
>> + Allow kexec to hand over state across kernels by generating and
>> + passing additional metadata to the target kernel. This is useful
>> + to keep data or state alive across the kexec. For this to work,
>> + both source and target kernels need to have this option enabled.
> Why do we have the same kconfig entry twice? Here and x86.
This was how the kexec config options were done when I wrote the patches
originally. Since then, looks like Eric DeVolder has cleaned up things
quite nicely. I'll adapt the new way.
>
>> +
>> config TRANS_TABLE
>> def_bool y
>> depends on HIBERNATION || KEXEC_CORE
>> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
>> index 417a8a86b2db..8035b673d96d 100644
>> --- a/arch/arm64/kernel/setup.c
>> +++ b/arch/arm64/kernel/setup.c
>> @@ -346,6 +346,8 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
>>
>> paging_init();
>>
>> + kho_reserve_mem();
>> +
>> acpi_table_upgrade();
>>
>> /* Parse the ACPI tables for possible boot-time configuration */
>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>> index 74c1db8ce271..254d82f3383a 100644
>> --- a/arch/arm64/mm/init.c
>> +++ b/arch/arm64/mm/init.c
>> @@ -358,6 +358,8 @@ void __init bootmem_init(void)
>> */
>> arch_reserve_crashkernel();
>>
>> + kho_reserve();
>> +
> reserve what? It is not obvious what the difference between
> kho_reserve_mem() and kho_reserve() are.
Yeah, I agree. I was struggling to find good names for them. What they
do is:
kho_reserve() - Reserve CMA memory for later kexec. We use this memory
region as scratch memory later.
kho_reserve_mem() - Post-KHO. Creates memory reservations inside
memblocks for pre-KHO handed over memory.
For v2, I'll change them to kho_reserve_scratch() and
kho_reserve_previous_mem() unless you have better ideas :)
>
>> memblock_dump_all();
>> }
>>
>> @@ -386,6 +388,12 @@ void __init mem_init(void)
>> /* this will put all unused low memory onto the freelists */
>> memblock_free_all();
>>
>> + /*
>> + * Now that all KHO pages are marked as reserved, let's flip them back
>> + * to normal pages with accurate refcount.
>> + */
>> + kho_populate_refcount();
>> +
>> /*
>> * Check boundaries twice: Some fundamental inconsistencies can be
>> * detected at build time already.
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index bf502ba8da95..af95139351ed 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -1006,6 +1006,44 @@ void __init early_init_dt_check_for_usable_mem_range(void)
>> memblock_add(rgn[i].base, rgn[i].size);
>> }
>>
>> +/**
>> + * early_init_dt_check_kho - Decode info required for kexec handover from DT
>> + */
>> +void __init early_init_dt_check_kho(void)
>> +{
>> +#ifdef CONFIG_KEXEC_KHO
> if (!IS_ENABLED(CONFIG_KEXEC_KHO))
> return;
>
> You'll need a kho_populate() stub.
Always happy to remove #ifdefs :)
>
>> + unsigned long node = chosen_node_offset;
>> + u64 kho_start, scratch_start, scratch_size, mem_start, mem_size;
>> + const __be32 *p;
>> + int l;
>> +
>> + if ((long)node < 0)
>> + return;
>> +
>> + p = of_get_flat_dt_prop(node, "linux,kho-dt", &l);
>> + if (l != (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32))
>> + return;
>> +
>> + kho_start = dt_mem_next_cell(dt_root_addr_cells, &p);
>> +
>> + p = of_get_flat_dt_prop(node, "linux,kho-scratch", &l);
>> + if (l != (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32))
>> + return;
>> +
>> + scratch_start = dt_mem_next_cell(dt_root_addr_cells, &p);
>> + scratch_size = dt_mem_next_cell(dt_root_addr_cells, &p);
>> +
>> + p = of_get_flat_dt_prop(node, "linux,kho-mem", &l);
>> + if (l != (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32))
>> + return;
>> +
>> + mem_start = dt_mem_next_cell(dt_root_addr_cells, &p);
>> + mem_size = dt_mem_next_cell(dt_root_addr_cells, &p);
>> +
>> + kho_populate(kho_start, scratch_start, scratch_size, mem_start, mem_size);
>> +#endif
>> +}
>> +
>> #ifdef CONFIG_SERIAL_EARLYCON
>>
>> int __init early_init_dt_scan_chosen_stdout(void)
>> @@ -1304,6 +1342,9 @@ void __init early_init_dt_scan_nodes(void)
>>
>> /* Handle linux,usable-memory-range property */
>> early_init_dt_check_for_usable_mem_range();
>> +
>> + /* Handle kexec handover */
>> + early_init_dt_check_kho();
>> }
>>
>> bool __init early_init_dt_scan(void *params)
>> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
>> index 68278340cecf..a612e6bb8c75 100644
>> --- a/drivers/of/kexec.c
>> +++ b/drivers/of/kexec.c
>> @@ -264,6 +264,37 @@ static inline int setup_ima_buffer(const struct kimage *image, void *fdt,
>> }
>> #endif /* CONFIG_IMA_KEXEC */
>>
>> +static int kho_add_chosen(const struct kimage *image, void *fdt, int chosen_node)
>> +{
>> + int ret = 0;
>> +
>> +#ifdef CONFIG_KEXEC_KHO
> ditto
>
> Though perhaps image->kho is not defined?
Correct, it is not. But I'm happy to have a few local variables that I
stash the image->kho contents inside an ifdef into so we can at least
compile check all libfdt invocations.
Alex
Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879
More information about the kexec
mailing list