[PATCH 1/3] fixup mmu_features immediately after getting cpu pa features.

Sourabh Jain
2021-10-04T15:11:59Z

From: Mahesh Salgaonkar <mahesh@linux.ibm.com>

On system with radix support available, early_radix_enabled() starts
returning true for a small window (until mmu_early_init_devtree() is
called) even when radix mode disabled on kernel command line. This causes
ppc64_bolted_size() to return ULONG_MAX in HPT mode instead of supported
segment size, during boot cpu paca allocation.

With kernel command line = "... disable_radix":

early_init_devtree: <- early_radix_enabled() = false
early_init_dt_scan_cpus: <- early_radix_enabled() = false
...
check_cpu_pa_features: <- early_radix_enabled() = false
... ^ <- early_radix_enabled() = TRUE
allocate_paca: | <- early_radix_enabled() = TRUE
... |
ppc64_bolted_size: | <- early_radix_enabled() = TRUE
if (early_radix_enabled())| <- early_radix_enabled() = TRUE
return ULONG_MAX; |
... |
... | <- early_radix_enabled() = TRUE
... | <- early_radix_enabled() = TRUE
mmu_early_init_devtree() V
... <- early_radix_enabled() = false

So far we have not seen any issue because allocate_paca() takes minimum of
ppc64_bolted_size and rma_size while allocating paca. However it is better
to close this window by fixing up the mmu features as early as possible.
This fixes early_radix_enabled() and ppc64_bolted_size() to return valid
values in radix disable mode. This patch will help subsequent patch to
depend on early_radix_enabled() check while detecting supported segment
size in HPT mode.

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Reported-and-tested-by: Abdul haleem <abdhalee@linux.vnet.ibm.com>
---
arch/powerpc/include/asm/book3s/64/mmu.h | 1 +
arch/powerpc/include/asm/mmu.h | 1 +
arch/powerpc/kernel/prom.c | 1 +
arch/powerpc/mm/init_64.c | 5 ++++-
4 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
index c02f42d1031e..69a89fa1330d 100644
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h
@@ -197,6 +197,7 @@ extern int mmu_vmemmap_psize;
extern int mmu_io_psize;

/* MMU initialization */
+void mmu_cpu_feature_fixup(void);
void mmu_early_init_devtree(void);
void hash__early_init_devtree(void);
void radix__early_init_devtree(void);
diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
index 8abe8e42e045..c8eafd401fe9 100644
--- a/arch/powerpc/include/asm/mmu.h
+++ b/arch/powerpc/include/asm/mmu.h
@@ -401,6 +401,7 @@ extern void early_init_mmu(void);
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_cpu_feature_fixup(void) { }
static inline void mmu_early_init_devtree(void) { }

static inline void pkey_early_init_devtree(void) {}
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 2e67588f6f6e..1727a3abe6c1 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -380,6 +380,7 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
check_cpu_pa_features(node);
}

+ mmu_cpu_feature_fixup();
identical_pvr_fixup(node);
init_mmu_slb_size(node);

diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
index 386be136026e..9ed452605a2c 100644
--- a/arch/powerpc/mm/init_64.c
+++ b/arch/powerpc/mm/init_64.c
@@ -437,12 +437,15 @@ static void __init early_check_vec5(void)
}
}

-void __init mmu_early_init_devtree(void)
+void __init mmu_cpu_feature_fixup(void)
{
/* Disable radix mode based on kernel command line. */
if (disable_radix)
cur_cpu_spec->mmu_features &= ~MMU_FTR_TYPE_RADIX;
+}

+void __init mmu_early_init_devtree(void)
+{
/*
* Check /chosen/ibm,architecture-vec-5 if running as a guest.
* When running bare-metal, we can use radix if we like
--
2.31.1