[PATCH v4 1/3] powerpc/fadump: Refactor and prepare fadump_cma_init for late init

[PATCH v4 1/3] powerpc/fadump: Refactor and prepare fadump_cma_init for late init

[Ritesh Harjani (IBM)]

We anyway don't use any return values from fadump_cma_init(). Since
fadump_reserve_mem() from where fadump_cma_init() gets called today,
already has the required checks.
This patch makes this function return type as void. Let's also handle
extra cases like return if fadump_supported is false or dump_active, so
that in later patches we can call fadump_cma_init() separately from
setup_arch().

Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---

v3 -> v4
=========
1. Dropped RFC tag.
2. Updated commit subject from fadump: <> powerpc/fadump:
3. Added RvBs and Acks.
[v3]: https://lore.kernel.org/linuxppc-dev/030b6d46fddac126a6cf7e119bea48055338f0ed.1728658614.git.ritesh.list@gmail.com/

 arch/powerpc/kernel/fadump.c | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index a612e7513a4f..162327d66982 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -78,27 +78,23 @@ static struct cma *fadump_cma;
  * But for some reason even if it fails we still have the memory reservation
  * with us and we can still continue doing fadump.
  */
-static int __init fadump_cma_init(void)
+static void __init fadump_cma_init(void)
 {
 	unsigned long long base, size;
 	int rc;

-	if (!fw_dump.fadump_enabled)
-		return 0;
-
+	if (!fw_dump.fadump_supported || !fw_dump.fadump_enabled ||
+			fw_dump.dump_active)
+		return;
 	/*
 	 * Do not use CMA if user has provided fadump=nocma kernel parameter.
-	 * Return 1 to continue with fadump old behaviour.
 	 */
-	if (fw_dump.nocma)
-		return 1;
+	if (fw_dump.nocma || !fw_dump.boot_memory_size)
+		return;

 	base = fw_dump.reserve_dump_area_start;
 	size = fw_dump.boot_memory_size;

-	if (!size)
-		return 0;
-
 	rc = cma_init_reserved_mem(base, size, 0, "fadump_cma", &fadump_cma);
 	if (rc) {
 		pr_err("Failed to init cma area for firmware-assisted dump,%d\n", rc);
@@ -108,7 +104,7 @@ static int __init fadump_cma_init(void)
 		 * blocked from production system usage.  Hence return 1,
 		 * so that we can continue with fadump.
 		 */
-		return 1;
+		return;
 	}

 	/*
@@ -125,10 +121,9 @@ static int __init fadump_cma_init(void)
 		cma_get_size(fadump_cma),
 		(unsigned long)cma_get_base(fadump_cma) >> 20,
 		fw_dump.reserve_dump_area_size);
-	return 1;
 }
 #else
-static int __init fadump_cma_init(void) { return 1; }
+static void __init fadump_cma_init(void) { }
 #endif /* CONFIG_CMA */

 /*
@@ -638,7 +633,7 @@ int __init fadump_reserve_mem(void)
 		pr_info("Reserved %lldMB of memory at %#016llx (System RAM: %lldMB)\n",
 			(size >> 20), base, (memblock_phys_mem_size() >> 20));

-		ret = fadump_cma_init();
+		fadump_cma_init();
 	}

 	return ret;
--
2.46.0

[PATCH v4 2/3] powerpc/fadump: Reserve page-aligned boot_memory_size during fadump_reserve_mem

[Ritesh Harjani (IBM)]

This patch refactors all CMA related initialization and alignment code
to within fadump_cma_init() which gets called in the end. This also means
that we keep [reserve_dump_area_start, boot_memory_size] page aligned
during fadump_reserve_mem(). Then later in fadump_cma_init() we extract the
aligned chunk and provide it to CMA. This inherently also fixes an issue in
the current code where the reserve_dump_area_start is not aligned
when the physical memory can have holes and the suitable chunk starts at
an unaligned boundary.

After this we should be able to call fadump_cma_init() independently
later in setup_arch() where pageblock_order is non-zero.

Suggested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 arch/powerpc/kernel/fadump.c | 34 ++++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 162327d66982..ffaec625b7a8 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -80,7 +80,7 @@ static struct cma *fadump_cma;
  */
 static void __init fadump_cma_init(void)
 {
-	unsigned long long base, size;
+	unsigned long long base, size, end;
 	int rc;

 	if (!fw_dump.fadump_supported || !fw_dump.fadump_enabled ||
@@ -92,8 +92,24 @@ static void __init fadump_cma_init(void)
 	if (fw_dump.nocma || !fw_dump.boot_memory_size)
 		return;

+	/*
+	 * [base, end) should be reserved during early init in
+	 * fadump_reserve_mem(). No need to check this here as
+	 * cma_init_reserved_mem() already checks for overlap.
+	 * Here we give the aligned chunk of this reserved memory to CMA.
+	 */
 	base = fw_dump.reserve_dump_area_start;
 	size = fw_dump.boot_memory_size;
+	end = base + size;
+
+	base = ALIGN(base, CMA_MIN_ALIGNMENT_BYTES);
+	end = ALIGN_DOWN(end, CMA_MIN_ALIGNMENT_BYTES);
+	size = end - base;
+
+	if (end <= base) {
+		pr_warn("%s: Too less memory to give to CMA\n", __func__);
+		return;
+	}

 	rc = cma_init_reserved_mem(base, size, 0, "fadump_cma", &fadump_cma);
 	if (rc) {
@@ -116,11 +132,12 @@ static void __init fadump_cma_init(void)
 	/*
 	 * So we now have successfully initialized cma area for fadump.
 	 */
-	pr_info("Initialized 0x%lx bytes cma area at %ldMB from 0x%lx "
+	pr_info("Initialized [0x%llx, %luMB] cma area from [0x%lx, %luMB] "
 		"bytes of memory reserved for firmware-assisted dump\n",
-		cma_get_size(fadump_cma),
-		(unsigned long)cma_get_base(fadump_cma) >> 20,
-		fw_dump.reserve_dump_area_size);
+		cma_get_base(fadump_cma), cma_get_size(fadump_cma) >> 20,
+		fw_dump.reserve_dump_area_start,
+		fw_dump.boot_memory_size >> 20);
+	return;
 }
 #else
 static void __init fadump_cma_init(void) { }
@@ -553,13 +570,6 @@ int __init fadump_reserve_mem(void)
 	if (!fw_dump.dump_active) {
 		fw_dump.boot_memory_size =
 			PAGE_ALIGN(fadump_calculate_reserve_size());
-#ifdef CONFIG_CMA
-		if (!fw_dump.nocma) {
-			fw_dump.boot_memory_size =
-				ALIGN(fw_dump.boot_memory_size,
-				      CMA_MIN_ALIGNMENT_BYTES);
-		}
-#endif

 		bootmem_min = fw_dump.ops->fadump_get_bootmem_min();
 		if (fw_dump.boot_memory_size < bootmem_min) {
--
2.46.0

[PATCH v4 3/3] powerpc/fadump: Move fadump_cma_init to setup_arch() after initmem_init()

[Ritesh Harjani (IBM)]

During early init CMA_MIN_ALIGNMENT_BYTES can be PAGE_SIZE,
since pageblock_order is still zero and it gets initialized
later during initmem_init() e.g.
setup_arch() -> initmem_init() -> sparse_init() -> set_pageblock_order()

One such use case where this causes issue is -
early_setup() -> early_init_devtree() -> fadump_reserve_mem() -> fadump_cma_init()

This causes CMA memory alignment check to be bypassed in
cma_init_reserved_mem(). Then later cma_activate_area() can hit
a VM_BUG_ON_PAGE(pfn & ((1 << order) - 1)) if the reserved memory
area was not pageblock_order aligned.

Fix it by moving the fadump_cma_init() after initmem_init(),
where other such cma reservations also gets called.

<stack trace>
==============
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10010
flags: 0x13ffff800000000(node=1|zone=0|lastcpupid=0x7ffff) CMA
raw: 013ffff800000000 5deadbeef0000100 5deadbeef0000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: VM_BUG_ON_PAGE(pfn & ((1 << order) - 1))
------------[ cut here ]------------
kernel BUG at mm/page_alloc.c:778!

Call Trace:
__free_one_page+0x57c/0x7b0 (unreliable)
free_pcppages_bulk+0x1a8/0x2c8
free_unref_page_commit+0x3d4/0x4e4
free_unref_page+0x458/0x6d0
init_cma_reserved_pageblock+0x114/0x198
cma_init_reserved_areas+0x270/0x3e0
do_one_initcall+0x80/0x2f8
kernel_init_freeable+0x33c/0x530
kernel_init+0x34/0x26c
ret_from_kernel_user_thread+0x14/0x1c

Fixes: 11ac3e87ce09 ("mm: cma: use pageblock_order as the single alignment")
Suggested-by: David Hildenbrand <david@redhat.com>
Reported-by: Sachin P Bappalige <sachinpb@linux.ibm.com>
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 arch/powerpc/include/asm/fadump.h  | 7 +++++++
 arch/powerpc/kernel/fadump.c       | 6 +-----
 arch/powerpc/kernel/setup-common.c | 6 ++++--
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/include/asm/fadump.h b/arch/powerpc/include/asm/fadump.h
index ef40c9b6972a..3638f04447f5 100644
--- a/arch/powerpc/include/asm/fadump.h
+++ b/arch/powerpc/include/asm/fadump.h
@@ -34,4 +34,11 @@ extern int early_init_dt_scan_fw_dump(unsigned long node, const char *uname,
 				      int depth, void *data);
 extern int fadump_reserve_mem(void);
 #endif
+
+#if defined(CONFIG_FA_DUMP) && defined(CONFIG_CMA)
+void fadump_cma_init(void);
+#else
+static inline void fadump_cma_init(void) { }
+#endif
+
 #endif /* _ASM_POWERPC_FADUMP_H */
diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index ffaec625b7a8..c42f89862893 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -78,7 +78,7 @@ static struct cma *fadump_cma;
  * But for some reason even if it fails we still have the memory reservation
  * with us and we can still continue doing fadump.
  */
-static void __init fadump_cma_init(void)
+void __init fadump_cma_init(void)
 {
 	unsigned long long base, size, end;
 	int rc;
@@ -139,8 +139,6 @@ static void __init fadump_cma_init(void)
 		fw_dump.boot_memory_size >> 20);
 	return;
 }
-#else
-static void __init fadump_cma_init(void) { }
 #endif /* CONFIG_CMA */

 /*
@@ -642,8 +640,6 @@ int __init fadump_reserve_mem(void)

 		pr_info("Reserved %lldMB of memory at %#016llx (System RAM: %lldMB)\n",
 			(size >> 20), base, (memblock_phys_mem_size() >> 20));
-
-		fadump_cma_init();
 	}

 	return ret;
diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index 943430077375..b6b01502e504 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -997,9 +997,11 @@ void __init setup_arch(char **cmdline_p)
 	initmem_init();

 	/*
-	 * Reserve large chunks of memory for use by CMA for KVM and hugetlb. These must
-	 * be called after initmem_init(), so that pageblock_order is initialised.
+	 * Reserve large chunks of memory for use by CMA for fadump, KVM and
+	 * hugetlb. These must be called after initmem_init(), so that
+	 * pageblock_order is initialised.
 	 */
+	fadump_cma_init();
 	kvm_cma_reserve();
 	gigantic_hugetlb_cma_reserve();

--
2.46.0

Re: [PATCH v4 1/3] powerpc/fadump: Refactor and prepare fadump_cma_init for late init

[Michael Ellerman]

On Fri, 18 Oct 2024 21:47:55 +0530, Ritesh Harjani (IBM) wrote:
> We anyway don't use any return values from fadump_cma_init(). Since
> fadump_reserve_mem() from where fadump_cma_init() gets called today,
> already has the required checks.
> This patch makes this function return type as void. Let's also handle
> extra cases like return if fadump_supported is false or dump_active, so
> that in later patches we can call fadump_cma_init() separately from
> setup_arch().
> 
> [...]

Applied to powerpc/next.

[1/3] powerpc/fadump: Refactor and prepare fadump_cma_init for late init
      https://git.kernel.org/powerpc/c/adfaec30ffaceecd565e06adae367aa944acc3c9
[2/3] powerpc/fadump: Reserve page-aligned boot_memory_size during fadump_reserve_mem
      https://git.kernel.org/powerpc/c/6faeac507beb2935d9171a01c3877b0505689c58
[3/3] powerpc/fadump: Move fadump_cma_init to setup_arch() after initmem_init()
      https://git.kernel.org/powerpc/c/05b94cae1c47f94588c3e7096963c1007c4d9c1d

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