linux-kernel - [PATCH 2/2] kexec_file: Load kernel at top of system RAM if required

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Date:   Thu, 22 Mar 2018 11:37:22 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     kexec@...ts.infradead.org, akpm@...ux-foundation.org,
        takahiro.akashi@...aro.org, ebiederm@...ssion.com,
        vgoyal@...hat.com, dyoung@...hat.com, prudo@...ux.vnet.ibm.com,
        Baoquan He <bhe@...hat.com>
Subject: [PATCH 2/2] kexec_file: Load kernel at top of system RAM if required

For kexec_file loading, if kexec_buf.top_down is 'true', the memory which
is used to load kernel/initrd/purgatory is supposed to be allocated from
top to down. This is also consistent with the old kexec loading interface.

However, the current arch_kexec_walk_mem() doesn't do like this. It ignores
checking kexec_buf.top_down, bug calls walk_system_ram_res() directly to go
through all resources of System RAM, to try to find memory region which can
contain the specific kexec buffer, then call locate_mem_hole_callback() to
allocate memory in that found memory region from top to down. This is not
right.

Here add checking if kexec_buf.top_down is 'true' in arch_kexec_walk_mem(),
if yes, call the newly added walk_system_ram_res_rev() to find memory region
from top to down to load kernel.

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 kernel/kexec_file.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 57ec39995b23..76e6307f8971 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -445,6 +445,8 @@ int __weak arch_kexec_walk_mem(struct kexec_buf *kbuf,
 					   IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
 					   crashk_res.start, crashk_res.end,
 					   kbuf, func);
+	else if (kbuf->top_down)
+		return walk_system_ram_res_rev(0, ULONG_MAX, kbuf, func);
 	else
 		return walk_system_ram_res(0, ULONG_MAX, kbuf, func);
 }
-- 
2.13.6