linux-kernel - [RFC PATCH v2 4/4] mm,memory_hotplug: Enable MHP_MEMMAP_ON

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Date:   Wed, 25 Nov 2020 12:20:48 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     david@...hat.com
Cc:     mhocko@...nel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, vbabka@...e.cz, pasha.tatashin@...een.com,
        Oscar Salvador <osalvador@...e.de>
Subject: [RFC PATCH v2 4/4] mm,memory_hotplug: Enable MHP_MEMMAP_ON_MEMORY when supported

Let the callers check whether they can use MHP_MEMMAP_ON_MEMORY by
checking mhp_supports_memmap_on_memory().
Currently, we only support MHP_MEMMAP_ON_MEMORY in case
CONFIG_SPARSEMEM_VMEMMAP is enabled, the architecture supports altmap,
and the range to be added spans a single memory block.

Signed-off-by: Oscar Salvador <osalvador@...e.de>
---
 drivers/acpi/acpi_memhotplug.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index b02fd51e5589..1fe645ef0b6c 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -172,6 +172,7 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
 	int result, num_enabled = 0;
 	struct acpi_memory_info *info;
 	int node;
+	mhp_t mhp_flags = MHP_NONE;
 
 	node = acpi_get_node(handle);
 	/*
@@ -194,8 +195,10 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
 		if (node < 0)
 			node = memory_add_physaddr_to_nid(info->start_addr);
 
+		if (mhp_supports_memmap_on_memory(info->length))
+			mhp_flags |= MHP_MEMMAP_ON_MEMORY;
 		result = __add_memory(node, info->start_addr, info->length,
-				      MHP_NONE);
+				      mhp_flags);
 
 		/*
 		 * If the memory block has been used by the kernel, add_memory()
-- 
2.26.2