On Tue, Oct 10, 2023 at 04:07:00PM +0530, Hari Bathini wrote:
>
>
> On 09/10/23 5:00 pm, Pingfan Liu wrote:
> > *** Idea ***
> > For kexec -p, the boot cpu can be not the cpu0, this causes the problem
> > of allocating memory for paca_ptrs[]. However, in theory, there is no
> > requirement to assign cpu's logical id as its present sequence in the
> > device tree. But there is something like cpu_first_thread_sibling(),
> > which makes assumption on the mapping inside a core. Hence partially
> > loosening the mapping, i.e. unbind the mapping of core while keep the
> > mapping inside a core.
> >
> > *** Implement ***
> > At this early stage, there are plenty of memory to utilize. Hence, this
> > patch allocates interim memory to link the cpu info on a list, then
> > reorder cpus by changing the list head. As a result, there is a rotate
> > shift between the sequence number in dt and the cpu logical number.
> >
> > *** Result ***
> > After this patch, a boot-cpu's logical id will always be mapped into the
> > range [0,threads_per_core).
> >
> > Besides this, at this phase, all threads in the boot core are forced to
> > be onlined. This restriction will be lifted in a later patch with
> > extra effort.
> >
> > Signed-off-by: Pingfan Liu <pi...@redhat.com>
> > Cc: Michael Ellerman <m...@ellerman.id.au>
> > Cc: Nicholas Piggin <npig...@gmail.com>
> > Cc: Christophe Leroy <christophe.le...@csgroup.eu>
> > Cc: Mahesh Salgaonkar <mah...@linux.ibm.com>
> > Cc: Wen Xiong <wenxi...@us.ibm.com>
> > Cc: Baoquan He <b...@redhat.com>
> > Cc: Ming Lei <ming....@redhat.com>
> > Cc: kexec@lists.infradead.org
> > To: linuxppc-...@lists.ozlabs.org
> > ---
> > arch/powerpc/kernel/prom.c | 25 +++++----
> > arch/powerpc/kernel/setup-common.c | 87 +++++++++++++++++++++++-------
> > 2 files changed, 85 insertions(+), 27 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> > index ec82f5bda908..87272a2d8c10 100644
> > --- a/arch/powerpc/kernel/prom.c
> > +++ b/arch/powerpc/kernel/prom.c
> > @@ -76,7 +76,9 @@ u64 ppc64_rma_size;
> > unsigned int boot_cpu_node_count __ro_after_init;
> > #endif
> > static phys_addr_t first_memblock_size;
> > +#ifdef CONFIG_SMP
> > static int __initdata boot_cpu_count;
> > +#endif
> > static int __init early_parse_mem(char *p)
> > {
> > @@ -331,8 +333,7 @@ static int __init early_init_dt_scan_cpus(unsigned long
> > node,
> > const __be32 *intserv;
> > int i, nthreads;
> > int len;
> > - int found = -1;
> > - int found_thread = 0;
> > + bool found = false;
> > /* We are scanning "cpu" nodes only */
> > if (type == NULL || strcmp(type, "cpu") != 0)
> > @@ -355,8 +356,15 @@ static int __init early_init_dt_scan_cpus(unsigned
> > long node,
> > for (i = 0; i < nthreads; i++) {
> > if (be32_to_cpu(intserv[i]) ==
> > fdt_boot_cpuid_phys(initial_boot_params)) {
> > - found = boot_cpu_count;
> > - found_thread = i;
> > + /*
> > + * always map the boot-cpu logical id into the
> > + * range of [0, thread_per_core)
> > + */
> > + boot_cpuid = i;
> > + found = true;
> > + /* This works around the hole in paca_ptrs[]. */
> > + if (nr_cpu_ids < nthreads)
> > + set_nr_cpu_ids(nthreads);
> > }
> > #ifdef CONFIG_SMP
> > /* logical cpu id is always 0 on UP kernels */
> > @@ -365,14 +373,13 @@ static int __init early_init_dt_scan_cpus(unsigned
> > long node,
> > }
> > /* Not the boot CPU */
> > - if (found < 0)
> > + if (!found)
> > return 0;
> > - DBG("boot cpu: logical %d physical %d\n", found,
> > - be32_to_cpu(intserv[found_thread]));
> > - boot_cpuid = found;
> > + DBG("boot cpu: logical %d physical %d\n", boot_cpuid,
> > + be32_to_cpu(intserv[boot_cpuid]));
> > - boot_cpu_hwid = be32_to_cpu(intserv[found_thread]);
> > + boot_cpu_hwid = be32_to_cpu(intserv[boot_cpuid]);
> > /*
> > * PAPR defines "logical" PVR values for cpus that
> > diff --git a/arch/powerpc/kernel/setup-common.c
> > b/arch/powerpc/kernel/setup-common.c
> > index 1b19a9815672..81291e13dec0 100644
> > --- a/arch/powerpc/kernel/setup-common.c
> > +++ b/arch/powerpc/kernel/setup-common.c
> > @@ -36,6 +36,7 @@
> > #include <linux/of_platform.h>
> > #include <linux/hugetlb.h>
> > #include <linux/pgtable.h>
> > +#include <linux/list.h>
> > #include <asm/io.h>
> > #include <asm/paca.h>
> > #include <asm/processor.h>
> > @@ -425,6 +426,13 @@ static void __init cpu_init_thread_core_maps(int tpc)
> > u32 *cpu_to_phys_id = NULL;
> > +struct interrupt_server_node {
> > + struct list_head node;
> > + bool avail;
> > + int len;
> > + __be32 *intserv;
> > +};
> > +
> > /**
> > * setup_cpu_maps - initialize the following cpu maps:
> > * cpu_possible_mask
> > @@ -446,11 +454,16 @@ u32 *cpu_to_phys_id = NULL;
> > void __init smp_setup_cpu_maps(void)
> > {
> > struct device_node *dn;
> > - int cpu = 0;
> > - int nthreads = 1;
> > + int shift = 0, cpu = 0;
> > + int j, nthreads = 1;
> > + int len;
> > + struct interrupt_server_node *intserv_node, *n;
> > + struct list_head *bt_node, head;
> > + bool avail, found_boot_cpu = false;
> > DBG("smp_setup_cpu_maps()\n");
> > + INIT_LIST_HEAD(&head);
> > cpu_to_phys_id = memblock_alloc(nr_cpu_ids * sizeof(u32),
> > __alignof__(u32));
> > if (!cpu_to_phys_id)
> > @@ -460,7 +473,6 @@ void __init smp_setup_cpu_maps(void)
> > for_each_node_by_type(dn, "cpu") {
> > const __be32 *intserv;
> > __be32 cpu_be;
> > - int j, len;
> > DBG(" * %pOF...\n", dn);
> > @@ -480,29 +492,68 @@ void __init smp_setup_cpu_maps(void)
> > }
> > }
> > - nthreads = len / sizeof(int);
> > + avail = of_device_is_available(dn);
> > + if (!avail)
> > + avail = !of_property_match_string(dn,
> > + "enable-method", "spin-table");
> > - for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
> > - bool avail;
> > - DBG(" thread %d -> cpu %d (hard id %d)\n",
> > - j, cpu, be32_to_cpu(intserv[j]));
> > -
> > - avail = of_device_is_available(dn);
> > - if (!avail)
> > - avail = !of_property_match_string(dn,
> > - "enable-method", "spin-table");
> > + intserv_node = memblock_alloc(sizeof(struct
> > interrupt_server_node) + len,
> > + __alignof__(u32));
> > + if (!intserv_node)
> > + panic("%s: Failed to allocate %zu bytes align=0x%zx\n",
> > + __func__,
> > + sizeof(struct interrupt_server_node) + len,
> > + __alignof__(u32));
>
> > + intserv_node->intserv = (__be32 *)((char *)intserv_node +
> > + sizeof(struct
> > interrupt_server_node));
>
> This initialization won't be needed if the member was:
>
> __be32 intserv[];
>
Thank you, I will use your suggestion.
> > + intserv_node->len = len;
> > + memcpy(intserv_node->intserv, intserv, len);
> > + intserv_node->avail = avail;
>
> > + INIT_LIST_HEAD(&intserv_node->node);
> > + list_add_tail(&intserv_node->node, &head);
>
> INIT_LIST_HEAD(&intserv_node->node); is not needed as list_add_tail()
> initializes both next & prev anyway.
>
You are right. I will remove the unnecessary initialization in the next
version.
Thanks,
Pingfan
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