linux-kernel - Re: [PATCH 2/8] kexec_file: Generalize kexec_add

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Date:	Mon, 13 Jun 2016 17:40:43 -0300
From:	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
To:	linuxppc-dev@...ts.ozlabs.org
Cc:	Dave Young <dyoung@...hat.com>, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Eric Biederman <ebiederm@...ssion.com>
Subject: Re: [PATCH 2/8] kexec_file: Generalize kexec_add_buffer.

Hi Dave,

Am Montag, 13 Juni 2016, 16:08:19 schrieb Thiago Jung Bauermann:
> Am Montag, 13 Juni 2016, 15:29:39 schrieb Dave Young:
> > On 06/12/16 at 12:10am, Thiago Jung Bauermann wrote:
> > > Allow architectures to specify different memory walking functions for
> > > kexec_add_buffer. Intel uses iomem to track reserved memory ranges,
> > > but PowerPC uses the memblock subsystem.
> > 
> > Can the crashk_res be inserted to iomem_resource so that only one
> > weak function for system ram is needed?
> 
> Sorry, it's not clear to me what you mean by inserting crashk_res into
> iomem_resource, but I can add a bool for_crashkernel to
> arch_walk_system_ram so that it can decide which kind of memory to
> traverse.

This is the patch implementing that idea. What do you think?
-- 
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center


    kexec_file: Generalize kexec_add_buffer.
    
    Allow architectures to specify different memory walking functions for
    kexec_add_buffer. Intel uses iomem to track reserved memory ranges,
    but PowerPC uses the memblock subsystem.
    
    Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
    Cc: Eric Biederman <ebiederm@...ssion.com>
    Cc: kexec@...ts.infradead.org
    Cc: linux-kernel@...r.kernel.org

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index e8acb2b43dd9..be18cb80c14e 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -315,6 +315,9 @@ int __weak arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr,
 					Elf_Shdr *sechdrs, unsigned int relsec);
 int __weak arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
 					unsigned int relsec);
+int __weak arch_walk_system_ram(bool for_crashkernel, unsigned long start,
+				unsigned long end, bool top_down, void *data,
+				int (*func)(u64, u64, void *));
 void arch_kexec_protect_crashkres(void);
 void arch_kexec_unprotect_crashkres(void);
 
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index b6eec7527e9f..5d0a6a20b12b 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -428,6 +428,38 @@ static int locate_mem_hole_callback(u64 start, u64 end, void *arg)
 	return locate_mem_hole_bottom_up(start, end, kbuf);
 }
 
+/**
+ * arch_walk_system_ram - call func(data) on free memory regions
+ * @for_crashkernel:	Is this for the crash kernel?
+ * @start:		Don't visit memory regions below this address.
+ * @end:		Don't visit memory regions above this address.
+ * @top_down:		Starts from the highest address?
+ * @data:		Argument to pass to @func.
+ * @func:		Function to call for each memory region.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+int __weak arch_walk_system_ram(bool for_crashkernel, unsigned long start,
+				unsigned long end, bool top_down, void *data,
+				int (*func)(u64, u64, void *))
+{
+	int ret;
+
+	if (for_crashkernel)
+		ret = walk_iomem_res_desc(crashk_res.desc,
+					  IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
+					  start, end, data, func);
+	else
+		ret = walk_system_ram_res(start, end, data, func);
+
+	if (ret != 1) {
+		/* A suitable memory range could not be found for buffer */
+		return -EADDRNOTAVAIL;
+	}
+
+	return 0;
+}
+
 /*
  * Helper function for placing a buffer in a kexec segment. This assumes
  * that kexec_mutex is held.
@@ -473,17 +505,14 @@ int kexec_add_buffer(struct kimage *image, char *buffer, unsigned long bufsz,
 
 	/* Walk the RAM ranges and allocate a suitable range for the buffer */
 	if (image->type == KEXEC_TYPE_CRASH)
-		ret = walk_iomem_res_desc(crashk_res.desc,
-				IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
-				crashk_res.start, crashk_res.end, kbuf,
-				locate_mem_hole_callback);
+		ret = arch_walk_system_ram(true, crashk_res.start,
+					   crashk_res.end, top_down, kbuf,
+					   locate_mem_hole_callback);
 	else
-		ret = walk_system_ram_res(0, -1, kbuf,
-					  locate_mem_hole_callback);
-	if (ret != 1) {
-		/* A suitable memory range could not be found for buffer */
-		return -EADDRNOTAVAIL;
-	}
+		ret = arch_walk_system_ram(false, 0, -1, top_down, kbuf,
+					   locate_mem_hole_callback);
+	if (ret)
+		return ret;
 
 	/* Found a suitable memory range */
 	ksegment = &image->segment[image->nr_segments];