linux-kernel - [PATCH v2 2/3] kernel/resource: make walk_mem_res() find all busy IORESOURCE

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Date:   Thu, 25 Mar 2021 12:53:25 +0100
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Keith Busch <keith.busch@...el.com>,
        Michal Hocko <mhocko@...e.com>, Qian Cai <cai@....pw>,
        Oscar Salvador <osalvador@...e.de>,
        Eric Biederman <ebiederm@...ssion.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Brijesh Singh <brijesh.singh@....com>, x86@...nel.org,
        kexec@...ts.infradead.org
Subject: [PATCH v2 2/3] kernel/resource: make walk_mem_res() find all busy IORESOURCE_MEM resources

It used to be true that we can have system RAM (IORESOURCE_SYSTEM_RAM |
IORESOURCE_BUSY) only on the first level in the resource tree. However,
this is no longer holds for driver-managed system RAM (i.e., added via
dax/kmem and virtio-mem), which gets added on lower levels, for example,
inside device containers.

IORESOURCE_SYSTEM_RAM is defined as IORESOURCE_MEM | IORESOURCE_SYSRAM
and just a special type of IORESOURCE_MEM.

The function walk_mem_res() only consideres the first level and is
used in arch/x86/mm/ioremap.c:__ioremap_check_mem() only. We currently
fail to identify System RAM added by dax/kmem and virtio-mem as
"IORES_MAP_SYSTEM_RAM", for example, allowing for remapping of such
"normal RAM" in __ioremap_caller().

Let's find all IORESOURCE_MEM | IORESOURCE_BUSY resources, making the
function behave similar to walk_system_ram_res().

Fixes: ebf71552bb0e ("virtio-mem: Add parent resource for all added "System RAM"")
Fixes: c221c0b0308f ("device-dax: "Hotplug" persistent memory for use like normal RAM")
Reviewed-by: Dan Williams <dan.j.williams@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Cc: Dave Young <dyoung@...hat.com>
Cc: Baoquan He <bhe@...hat.com>
Cc: Vivek Goyal <vgoyal@...hat.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Keith Busch <keith.busch@...el.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Qian Cai <cai@....pw>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: Eric Biederman <ebiederm@...ssion.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Brijesh Singh <brijesh.singh@....com>
Cc: x86@...nel.org
Cc: kexec@...ts.infradead.org
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 kernel/resource.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 4efd6e912279..16e0c7e8ed24 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -470,7 +470,7 @@ int walk_mem_res(u64 start, u64 end, void *arg,
 {
 	unsigned long flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 
-	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, true,
+	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, false,
 				     arg, func);
 }
 
-- 
2.29.2