Re: [PATCH 2/2] powerpc/fadump: consider reserved ranges while reserving memory

Commit 0962e8004e97 ("powerpc/prom: Scan reserved-ranges node for
memory reservations") enabled support to parse reserved-ranges DT
node and reserve kernel memory falling in these ranges for F/W
purposes. Memory reserved for FADump should not overlap with these
ranges as it could corrupt memory meant for F/W or crash'ed kernel
memory to be exported as vmcore.

But since commit 579ca1a27675 ("powerpc/fadump: make use of memblock's
bottom up allocation mode"), memblock_find_in_range() is being used to
find the appropriate area to reserve memory for FADump, which can't
account for reserved-ranges as these ranges are reserved only after
FADump memory reservation.

With reserved-ranges now being populated during early boot, look out
for these memory ranges while reserving memory for FADump. Without
this change, MPIPL on PowerNV systems aborts with hostboot failure,
when memory reserved for FADump is less than 4096MB.

Fixes: 579ca1a27675 ("powerpc/fadump: make use of memblock's bottom up allocation mode")
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---
 arch/powerpc/kernel/fadump.c |   76 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 66 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 7fcf4a8f..ab83be9 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c

@@ -443,10 +443,70 @@ static int __init fadump_get_boot_mem_regions(void)
 	return ret;
 }
 
+/*
+ * Returns true, if the given range overlaps with reserved memory ranges
+ * starting at idx. Also, updates idx to index of overlapping memory range
+ * with the given memory range.
+ * False, otherwise.
+ */
+static bool overlaps_reserved_ranges(u64 base, u64 end, int *idx)
+{
+	bool ret = false;
+	int i;
+
+	for (i = *idx; i < reserved_mrange_info.mem_range_cnt; i++) {
+		u64 rbase = reserved_mrange_info.mem_ranges[i].base;
+		u64 rend = rbase + reserved_mrange_info.mem_ranges[i].size;
+
+		if (end <= rbase)
+			break;
+
+		if ((end > rbase) &&  (base < rend)) {
+			*idx = i;
+			ret = true;
+			break;
+		}
+	}
+
+	return ret;
+}
+
+/*
+ * Locate a suitable memory area to reserve memory for FADump. While at it,
+ * lookup reserved-ranges & avoid overlap with them, as they are used by F/W.
+ */
+static u64 __init fadump_locate_reserve_mem(u64 base, u64 size)
+{
+	struct fadump_memory_range *mrngs;
+	phys_addr_t mstart, mend;
+	int idx = 0;
+	u64 i;
+
+	mrngs = reserved_mrange_info.mem_ranges;
+	for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE,
+				&mstart, &mend, NULL) {
+		pr_debug("%llu) mstart: %llx, mend: %llx, base: %llx\n",
+			 i, mstart, mend, base);
+
+		if (mstart > base)
+			base = PAGE_ALIGN(mstart);
+
+		while ((mend > base) && ((mend - base) >= size)) {
+			if (!overlaps_reserved_ranges(base, base + size, &idx))
+				goto out;
+
+			base = mrngs[idx].base + mrngs[idx].size;
+			base = PAGE_ALIGN(base);