Re: [PATCH 3/3] s390/mm: Define arch_get_mappable_range()

On 12/8/20 8:57 PM, Heiko Carstens wrote:

On Tue, Dec 08, 2020 at 09:46:18AM +0530, Anshuman Khandual wrote:

quoted

This overrides arch_get_mappabble_range() on s390 platform which will be
used with recently added generic framework. It drops a redundant similar
check in vmem_add_mapping() while compensating __segment_load() with a new
address range check to preserve the existing functionality. It also adds a
VM_BUG_ON() check that would ensure that memhp_range_allowed() has already
been called on the hotplug path.

Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: David Hildenbrand <redacted>
Cc: linux-s390@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <redacted>
---
 arch/s390/mm/extmem.c |  5 +++++
 arch/s390/mm/init.c   | 10 ++++++++++
 arch/s390/mm/vmem.c   |  4 ----
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/s390/mm/extmem.c b/arch/s390/mm/extmem.c
index 5060956b8e7d..cc055a78f7b6 100644
--- a/arch/s390/mm/extmem.c
+++ b/arch/s390/mm/extmem.c

@@ -337,6 +337,11 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long
 		goto out_free_resource;
 	}
 
+	if (seg->end + 1 > VMEM_MAX_PHYS || seg->end + 1 < seg->start_addr) {
+		rc = -ERANGE;
+		goto out_resource;
+	}
+
 	rc = vmem_add_mapping(seg->start_addr, seg->end - seg->start_addr + 1);
 	if (rc)
 		goto out_resource;

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 77767850d0d0..64937baabf93 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c

@@ -278,6 +278,15 @@ device_initcall(s390_cma_mem_init);
 
 #endif /* CONFIG_CMA */
 
+struct range arch_get_mappable_range(void)
+{
+	struct range memhp_range;
+
+	memhp_range.start = 0;
+	memhp_range.end =  VMEM_MAX_PHYS;
+	return memhp_range;
+}
+
 int arch_add_memory(int nid, u64 start, u64 size,
 		    struct mhp_params *params)
 {

@@ -291,6 +300,7 @@ int arch_add_memory(int nid, u64 start, u64 size,
 	if (WARN_ON_ONCE(params->pgprot.pgprot != PAGE_KERNEL.pgprot))
 		return -EINVAL;
 
+	VM_BUG_ON(!memhp_range_allowed(start, size, 1));
 	rc = vmem_add_mapping(start, size);
 	if (rc)
 		return rc;

diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
index b239f2ba93b0..749eab43aa93 100644
--- a/arch/s390/mm/vmem.c
+++ b/arch/s390/mm/vmem.c

@@ -536,10 +536,6 @@ int vmem_add_mapping(unsigned long start, unsigned long size)
 {
 	int ret;
 
-	if (start + size > VMEM_MAX_PHYS ||
-	    start + size < start)
-		return -ERANGE;
-

Is there a reason why you added the memhp_range_allowed() check call
to arch_add_memory() instead of vmem_add_mapping()? If you would do

As I had mentioned previously, memhp_range_allowed() is available with
CONFIG_MEMORY_HOTPLUG but vmem_add_mapping() is always available. Hence
there will be a build failure in vmem_add_mapping() for the range check
memhp_range_allowed() without memory hotplug enabled.

that, then the extra code in __segment_load() wouldn't be
required.
Even though the error message from memhp_range_allowed() might be
highly confusing.

Alternatively leaving __segment_load() and vmem_add_memory() unchanged
will create three range checks i.e two memhp_range_allowed() and the
existing VMEM_MAX_PHYS check in vmem_add_mapping() on all the hotplug
paths, which is not optimal.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel