[PATCH] makedumpfile: Enable compressed dump formats for Xen

[Petr Tesarik]

On Tue, 28 Jul 2015 07:45:04 +0000
Atsushi Kumagai <ats-kumagai at wm.jp.nec.com> wrote:

> Hello Petr,
> 
> >Hello all,
> >
> >this patch enables compressed file formats for Xen. I was suprized
> >that nobody noticed earlier, given how trivial the change is. ;-)
> 
> Good catch.
> Since there is no Xen dump in the kdump-compressed format, is it also
> necessary to fix the crash ?

Yes, I have a patch set for crash, but I wanted to make sure the change
gets accepted in makedumpfile first. The crash patch set is rather
intrusive; if makedumpfile can actually produce such files, it makes it
easier for me to negotiate with Dave Anderson. ;-)

> BTW, I think we should fix the manuals as well. There are some wrong
> statements "-E option must be specified with this option" and
> some examples implicate that -E option is necessary to Xen dump.

Good point. Should I send it as a separate patch, or include it in a
patch set and resend?

Petr T

> Thanks
> Atsushi Kumagai
> 
> >Originally, the compressed KDUMP format was not sufficient for Xen
> >Dom0 dumps, because it did not contain required Xen-specific
> >information. However, all this info is stored in ELF notes, which
> >have been present in the compressed file since version 4, so there
> >is no longer any reason to restrict Xen dumps to ELF only.
> >
> >One minor fix is necessary. In a Xen dump, PFN refers to physical
> >pages _inside_ Dom0, but when compressing the whole file, the machine
> >pages are used in fact (although the variable is still called pfn).
> >Consequently, readmem() must interpret the address as a machine
> >address rather than Dom0 physical address when saving Xen files.
> >
> >Signed-off-by: Petr Tesarik <ptesarik at suse.com>
> >
> >diff --git a/makedumpfile.c b/makedumpfile.c
> >index de40932..2636036 100644
> >--- a/makedumpfile.c
> >+++ b/makedumpfile.c
> >@@ -6015,9 +6015,11 @@ int
> > read_pfn(mdf_pfn_t pfn, unsigned char *buf)
> > {
> > 	unsigned long long paddr;
> >+	int type_addr;
> >
> > 	paddr = pfn_to_paddr(pfn);
> >-	if (!readmem(PADDR, paddr, buf, info->page_size)) {
> >+	type_addr = is_xen_memory() ? MADDR_XEN : PADDR;
> >+	if (!readmem(type_addr, paddr, buf, info->page_size)) {
> > 		ERRMSG("Can't get the page data.\n");
> > 		return FALSE;
> > 	}
> >@@ -7654,12 +7656,6 @@ initial_xen(void)
> > 	MSG("Xen is not supported on powerpc.\n");
> > 	return FALSE;
> > #else
> >-	if(!info->flag_elf_dumpfile && !info->flag_dmesg) {
> >-		MSG("Specify '-E' option for Xen.\n");
> >-		MSG("Commandline parameter is invalid.\n");
> >-		MSG("Try `makedumpfile --help' for more
> >information.\n");
> >-		return FALSE;
> >-	}
> > #ifndef __x86_64__
> > 	if (DL_EXCLUDE_ZERO < info->max_dump_level) {
> > 		MSG("Dump_level is invalid. It should be 0 or
> > 1.\n");
> 
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