diff mbox series

[v3,1/4] powerpc/mmu: do MMU type discovery before crashkernel reservation

Message ID 20260824081202.264913-2-sourabhjain@linux.ibm.com (mailing list archive)
State New
Headers show
Series powerpc/kdump: Support high crashkernel reservation | expand

Commit Message

Sourabh Jain Aug. 24, 2026, 8:11 a.m. UTC 
Crashkernel reservation on high memory depends on the MMU type. In
particular, arch_reserve_crashkernel() needs to know whether the radix
MMU is enabled when selecting the crashkernel reservation.

arch_reserve_crashkernel() is intentionally called early during boot.
The crashkernel memory needs to be reserved before other components
make memory reservations, as those reservations could interfere with
finding a suitable region for the crashkernel at the required offset.
Therefore, moving arch_reserve_crashkernel() to a later point is not a
suitable solution.

Instead, make the MMU type available before arch_reserve_crashkernel()
is called. The MMU type is determined from the FDT and kernel
configuration and is recorded in cur_cpu_spec->mmu_features.

early_radix_enabled() uses cur_cpu_spec->mmu_features to determine
whether the radix MMU is enabled. However, the MMU type discovery was
previously performed as part of mmu_early_init_devtree(), which runs
after arch_reserve_crashkernel(). Split the MMU type discovery from the
rest of mmu_early_init_devtree() and perform it before
arch_reserve_crashkernel().

This makes early_radix_enabled() usable from
arch_reserve_crashkernel(), which will be used by the following patch
to select the appropriate crashkernel reservation on high memory.

Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 arch/powerpc/include/asm/book3s/64/mmu.h |  1 +
 arch/powerpc/include/asm/mmu.h           |  1 +
 arch/powerpc/kernel/prom.c               | 29 +++++++++++++-----------
 arch/powerpc/mm/init_64.c                | 26 +++++++++++++--------
 4 files changed, 34 insertions(+), 23 deletions(-)
diff mbox series

Patch

diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
index 48631365b48c..d820640f2739 100644
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h
@@ -208,6 +208,7 @@  extern int mmu_vmemmap_psize;
 
 /* MMU initialization */
 void mmu_early_init_devtree(void);
+void mmu_early_init_type(void);
 void hash__early_init_devtree(void);
 void radix__early_init_devtree(void);
 #ifdef CONFIG_PPC_PKEY
diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
index 5f9c5d436e17..da0b498bd475 100644
--- a/arch/powerpc/include/asm/mmu.h
+++ b/arch/powerpc/include/asm/mmu.h
@@ -384,6 +384,7 @@  extern void early_init_mmu_secondary(void);
 extern void setup_initial_memory_limit(phys_addr_t first_memblock_base,
 				       phys_addr_t first_memblock_size);
 static inline void mmu_early_init_devtree(void) { }
+static inline void mmu_early_init_type(void) { }
 
 static inline void pkey_early_init_devtree(void) {}
 
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 9ed9dde7d231..4fc53129e6ee 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -853,6 +853,22 @@  void __init early_init_devtree(void *params)
 	if (PHYSICAL_START > MEMORY_START)
 		memblock_reserve(MEMORY_START, int_vector_size);
 	reserve_kdump_trampoline();
+
+	DBG("Scanning CPUs ...\n");
+
+	dt_cpu_ftrs_scan();
+
+	/* Retrieve CPU related informations from the flat tree
+	 * (altivec support, boot CPU ID, ...)
+	 */
+	of_scan_flat_dt(early_init_dt_scan_cpus, NULL);
+	if (boot_cpuid < 0) {
+		printk("Failed to identify boot CPU !\n");
+		BUG();
+	}
+
+	mmu_early_init_type();
+
 #if defined(CONFIG_FA_DUMP) || defined(CONFIG_PRESERVE_FA_DUMP)
 	/*
 	 * If we fail to reserve memory for firmware-assisted dump then
@@ -884,19 +900,6 @@  void __init early_init_devtree(void *params)
 	 * FIXME .. and the initrd too? */
 	move_device_tree();
 
-	DBG("Scanning CPUs ...\n");
-
-	dt_cpu_ftrs_scan();
-
-	/* Retrieve CPU related informations from the flat tree
-	 * (altivec support, boot CPU ID, ...)
-	 */
-	of_scan_flat_dt(early_init_dt_scan_cpus, NULL);
-	if (boot_cpuid < 0) {
-		printk("Failed to identify boot CPU !\n");
-		BUG();
-	}
-
 	save_fscr_to_task();
 
 #if defined(CONFIG_SMP) && defined(CONFIG_PPC64)
diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
index 64f0df5bb5cd..4916ed230600 100644
--- a/arch/powerpc/mm/init_64.c
+++ b/arch/powerpc/mm/init_64.c
@@ -614,7 +614,8 @@  static void __init early_init_memory_block_size(void)
 	of_scan_flat_dt(probe_memory_block_size, &memory_block_size);
 }
 
-void __init mmu_early_init_devtree(void)
+
+void __init mmu_early_init_type(void)
 {
 	bool hvmode = !!(mfmsr() & MSR_HV);
 
@@ -626,6 +627,20 @@  void __init mmu_early_init_devtree(void)
 			pr_warn("WARNING: Ignoring cmdline option disable_radix\n");
 	}
 
+	/*
+	 * Check /chosen/ibm,architecture-vec-5 if running as a guest.
+	 * When running bare-metal, we can use radix if we like
+	 * even though the ibm,architecture-vec-5 property created by
+	 * skiboot doesn't have the necessary bits set.
+	 */
+	if (!hvmode)
+		early_check_vec5();
+}
+
+void __init mmu_early_init_devtree(void)
+{
+	bool hvmode = !!(mfmsr() & MSR_HV);
+
 	of_scan_flat_dt(dt_scan_mmu_pid_width, NULL);
 	if (hvmode && !mmu_lpid_bits) {
 		if (early_cpu_has_feature(CPU_FTR_ARCH_207S))
@@ -638,15 +653,6 @@  void __init mmu_early_init_devtree(void)
 			mmu_pid_bits = 20; /* POWER9-10 */
 	}
 
-	/*
-	 * Check /chosen/ibm,architecture-vec-5 if running as a guest.
-	 * When running bare-metal, we can use radix if we like
-	 * even though the ibm,architecture-vec-5 property created by
-	 * skiboot doesn't have the necessary bits set.
-	 */
-	if (!hvmode)
-		early_check_vec5();
-
 	early_init_memory_block_size();
 
 	if (early_radix_enabled()) {