[PATCH v2 1/7] xen: Improve calculation of beginning of virtual address space

[Daniel Kiper <daniel.kiper-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

Xen commit 4b28bf6ae90bd83fd1113d8bdc53c3266ffeb328 (x86: re-introduce
map_domain_page() et al) once again altered virtual address space.
Current algorithm calculating its start could not cope with that change.
New version establishes this value on the base of domain_list placement
and is more generic.

Similar patch was applied to crash tool.

Signed-off-by: Daniel Kiper <daniel.kiper-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
---
 arch/x86_64.c  |   16 +++++++++++-----
 makedumpfile.h |    2 --
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/x86_64.c b/arch/x86_64.c
index 8e61b20..d864a06 100644
--- a/arch/x86_64.c
+++ b/arch/x86_64.c
@@ -372,14 +372,20 @@ int get_xen_basic_info_x86_64(void)
 		info->xen_phys_start = info->xen_crash_info.v2->xen_phys_start;
 	}
 
+	info->xen_virt_start = SYMBOL(domain_list);
+
+	/*
+	 * Xen virtual mapping is aligned to 1 GiB boundary.
+	 * domain_list lives in bss which sits no more than
+	 * 1 GiB below beginning of virtual address space.
+	 */
+	info->xen_virt_start &= 0xffffffffc0000000;
+
 	if (info->xen_crash_info.com &&
-	    info->xen_crash_info.com->xen_major_version >= 4) {
-		info->xen_virt_start = XEN_VIRT_START_V4;
+	    info->xen_crash_info.com->xen_major_version >= 4)
 		info->directmap_virt_end = DIRECTMAP_VIRT_END_V4;
-	} else {
-		info->xen_virt_start = XEN_VIRT_START_V3;
+	else
 		info->directmap_virt_end = DIRECTMAP_VIRT_END_V3;
-	}
 
 	if (SYMBOL(pgd_l4) == NOT_FOUND_SYMBOL) {
 		ERRMSG("Can't get pml4.\n");
diff --git a/makedumpfile.h b/makedumpfile.h
index a5826e0..1a87500 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -1473,8 +1473,6 @@ int get_xen_info_x86(void);
 #define DIRECTMAP_VIRT_END_V3 (0xffff840000000000)
 #define DIRECTMAP_VIRT_END_V4 (0xffff880000000000)
 #define DIRECTMAP_VIRT_END    (info->directmap_virt_end)
-#define XEN_VIRT_START_V3     (0xffff828c80000000)
-#define XEN_VIRT_START_V4     (0xffff82c480000000)
 #define XEN_VIRT_START        (info->xen_virt_start)
 #define XEN_VIRT_END          (XEN_VIRT_START + (1UL << 30))
 #define FRAMETABLE_VIRT_START 0xffff82f600000000
-- 
1.7.10.4