Re: Add "--mem-usage" support for s390x

[Michael Holzheu <holzheu@linux.vnet.ibm.com>]

On Thu, 25 Sep 2014 17:44:12 +0800
Baoquan He <bhe@redhat.com> wrote:

> On 09/24/14 at 05:19pm, Michael Holzheu wrote:
> > On Tue, 23 Sep 2014 10:40:58 +0800
> > Baoquan He <bhe@redhat.com> wrote:

[snip]

> > > 
> > > Hi Michael, 
> > > 
> > > Please alse provide a get_versiondep_info_s390x since page_offset is
> > > needed in set_kcore_vmcoreinfo() and other information need it too, such
> > > as VMALLOC_START/VMEMMAP_START/MODULES_VADDR, if you want to provide a
> > > is_vmalloc_addr_s390x before initial() is called.
> > 
> > Hello Baoquan,
> > 
> > Thanks for the hint! I looked into the x86_64 implementation of 
> > get_versiondep_info() where version dependent constants are used
> > for vmalloc_start and others.
> > 
> > For s390x this is not so easy because vmalloc_start is dependent
> > on the memory size of the system (see setup_memory_end()
> > in arch/s390/kernel/setup.c). Unfortunately "info->max_mapnr"
> > is not set at that time.
> 
> I am not aware of s390 arch and memory layout. But I can explain what
> those versiondep_info are used for, hope they can help. In fact in
> x86_64, page_offset is got for set_kcore_vmcoreinfo(), there the
> vmcoreinfo_addr need be converted to kvaddr. Since vmcoreinfo_addr is a
> physical addr, we can't use it directly. And
> VMALLOC_START/VMEMMAP_START/MODULES_VADDR are all used to filter this
> virtual addr space region since our vmcore only care about the physical
> ram addr region.
> 
> If you need get these before they are used for s390 arch. If necessary
> you can build a different code flow if you can achive the goal. All
> these are all used to get dumpable load segments from kcore.

Isn't this a chicken-and-egg problem? In order to determine vmalloc start
I have to be able to read memory. But in order to read memory I have
to call get_kcore_dump_loads() first.

What about using /proc/iomem to find out if an address is a real address?

The following patch seems to work for me:
---
 elf_info.c     |    4 ++--
 makedumpfile.c |   26 ++++++++++++++++++++++++++
 makedumpfile.h |    1 +
 3 files changed, 29 insertions(+), 2 deletions(-)

--- a/elf_info.c
+++ b/elf_info.c
@@ -854,7 +854,7 @@ int get_kcore_dump_loads(void)
 
 	for (i = 0; i < num_pt_loads; ++i) {
 		struct pt_load_segment *p = &pt_loads[i];
-		if (is_vmalloc_addr(p->virt_start))
+		if (!is_real_addr(p->virt_start))
 			continue;
 		loads++;
 	}
@@ -874,7 +874,7 @@ int get_kcore_dump_loads(void)
 
 	for (i = 0, j = 0; i < num_pt_loads; ++i) {
 		struct pt_load_segment *p = &pt_loads[i];
-		if (is_vmalloc_addr(p->virt_start))
+		if (!is_real_addr(p->virt_start))
 			continue;
 		if (j >= loads)
 			return FALSE;
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -9227,6 +9227,32 @@ int is_crashkernel_mem_reserved(void)
 	return !!crash_reserved_mem_nr;
 }
 
+struct addr_check {
+	unsigned long addr;
+	int found;
+};
+
+static int real_addr_callback(void *data, int nr, char *str,
+			      unsigned long base, unsigned long length)
+{
+	struct addr_check *addr_check = data;
+	unsigned long addr = addr_check->addr;
+
+	if (addr >= base && addr < base + length) {
+		addr_check->found = 1;
+		return -1;
+	}
+	return 0;
+}
+
+int is_real_addr(unsigned long addr)
+{
+	struct addr_check addr_check = {addr, 0};
+
+	iomem_for_each_line("System RAM\n", real_addr_callback, &addr_check);
+	return addr_check.found;
+}
+
 static int get_page_offset(void)
 {
 	struct utsname utsname;
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -1567,6 +1567,7 @@ int read_disk_dump_header(struct disk_du
 int read_kdump_sub_header(struct kdump_sub_header *kh, char *filename);
 void close_vmcoreinfo(void);
 int close_files_for_creating_dumpfile(void);
+int is_real_addr(unsigned long addr);
 
 
 /*


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