powerpc/64: Move paca allocation to early_setup()

The early paca and boot cpuid dance is complicated and currently does
not quite work as expected for boot cpuid != 0 cases.

early_init_devtree() currently allocates the paca_ptrs and boot cpuid
paca, but until that returns and early_setup() calls setup_paca(), this
thread is currently still executing with smp_processor_id() == 0.

One problem this causes is the paca_ptrs[smp_processor_id()] pointer is
poisoned, so valid_emergency_stack() (any backtrace) and any similar
users will crash.

Another is that the hardware id which is set here will not be returned
by get_hard_smp_processor_id(smp_processor_id()), but it would work
correctly for boot_cpuid == 0, which could lead to difficult to
reproduce or find bugs. The hard id does not seem to be used by the rest
of early_init_devtree(), it just looks like all this code might have
been put here to allocate somewhere to store boot CPU hardware id while
scanning the devtree.

Rearrange things so the hwid is put in a global variable like
boot_cpuid, and do all the paca allocation and boot paca setup in the
64-bit early_setup() after we have everything ready to go.

The paca_ptrs[0] re-poisoning code in early_setup does not seem to have
ever worked, because paca_ptrs[0] was never not-poisoned when boot_cpuid
is not 0.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Fix build error on 32-bit]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221216115930.2667772-4-npiggin@gmail.com

diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 09f1790d0ae165c5475ffd2ec235776d98ddab9f..0ab3511a47d7762382656e71bb0ba76a84c10411 100644 (file)
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -295,7 +295,6 @@ extern void free_unused_pacas(void);
 
 #else /* CONFIG_PPC64 */
 
-static inline void allocate_paca_ptrs(void) { }
 static inline void allocate_paca(int cpu) { }
 static inline void free_unused_pacas(void) { }
 

diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index f63505d74932bf89eb6d657a60bf3356aff47e72..6c6cb53d704586844e55601616b1c82b3096e3fc 100644 (file)
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -26,6 +26,7 @@
 #include <asm/percpu.h>
 
 extern int boot_cpuid;
+extern int boot_cpu_hwid; /* PPC64 only */
 extern int spinning_secondaries;
 extern u32 *cpu_to_phys_id;
 extern bool coregroup_enabled;

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 4f1c920aa13ed5b0c5b0cb2e6890269a5d10ac46..f318e8e1f3fe47a853db393e75f7e9e87c2575a9 100644 (file)
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -370,8 +370,8 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
            be32_to_cpu(intserv[found_thread]));
        boot_cpuid = found;
 
-       // Pass the boot CPU's hard CPU id back to our caller
-       *((u32 *)data) = be32_to_cpu(intserv[found_thread]);
+       if (IS_ENABLED(CONFIG_PPC64))
+               boot_cpu_hwid = be32_to_cpu(intserv[found_thread]);
 
        /*
         * PAPR defines "logical" PVR values for cpus that
@@ -755,7 +755,6 @@ static inline void save_fscr_to_task(void) {}
 
 void __init early_init_devtree(void *params)
 {
-       u32 boot_cpu_hwid;
        phys_addr_t limit;
 
        DBG(" -> early_init_devtree(%px)\n", params);
@@ -851,7 +850,7 @@ void __init early_init_devtree(void *params)
        /* Retrieve CPU related informations from the flat tree
         * (altivec support, boot CPU ID, ...)
         */
-       of_scan_flat_dt(early_init_dt_scan_cpus, &boot_cpu_hwid);
+       of_scan_flat_dt(early_init_dt_scan_cpus, NULL);
        if (boot_cpuid < 0) {
                printk("Failed to identify boot CPU !\n");
                BUG();
@@ -868,11 +867,6 @@ void __init early_init_devtree(void *params)
 
        mmu_early_init_devtree();
 
-       // NB. paca is not installed until later in early_setup()
-       allocate_paca_ptrs();
-       allocate_paca(boot_cpuid);
-       set_hard_smp_processor_id(boot_cpuid, boot_cpu_hwid);
-
 #ifdef CONFIG_PPC_POWERNV
        /* Scan and build the list of machine check recoverable ranges */
        of_scan_flat_dt(early_init_dt_scan_recoverable_ranges, NULL);

diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index 9b10e57040c6c705f4b8ba0e17cd08d5e14b545e..e77734e5a127f98ca1af58b0180a1445e8e36837 100644 (file)
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -87,6 +87,10 @@ EXPORT_SYMBOL(machine_id);
 int boot_cpuid = -1;
 EXPORT_SYMBOL_GPL(boot_cpuid);
 
+#ifdef CONFIG_PPC64
+int boot_cpu_hwid = -1;
+#endif
+
 /*
  * These are used in binfmt_elf.c to put aux entries on the stack
  * for each elf executable being started.

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index a43865e0fb4bf21c799f019ffb616f5ad226d1bf..b2e0d3ce4261c08762b6a377c8600fc1888da45a 100644 (file)
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -385,15 +385,14 @@ void __init early_setup(unsigned long dt_ptr)
        /*
         * Do early initialization using the flattened device
         * tree, such as retrieving the physical memory map or
-        * calculating/retrieving the hash table size.
+        * calculating/retrieving the hash table size, discover
+        * boot_cpuid and boot_cpu_hwid.
         */
        early_init_devtree(__va(dt_ptr));
 
-       /* Now we know the logical id of our boot cpu, setup the paca. */
-       if (boot_cpuid != 0) {
-               /* Poison paca_ptrs[0] again if it's not the boot cpu */
-               memset(&paca_ptrs[0], 0x88, sizeof(paca_ptrs[0]));
-       }
+       allocate_paca_ptrs();
+       allocate_paca(boot_cpuid);
+       set_hard_smp_processor_id(boot_cpuid, boot_cpu_hwid);
        fixup_boot_paca(paca_ptrs[boot_cpuid]);
        setup_paca(paca_ptrs[boot_cpuid]); /* install the paca into registers */
        // smp_processor_id() now reports boot_cpuid