[PATCH Makedumpfile 2/4] x86_64: translate all VA to PA using page table values

[Pratyush Anand]

Currently we translate some of the VA areas using linear mapping while some
other(which can not be linearly mapped) using page table.

However, we will have entry of a page in the page table irrespective of its
virtual region. So, we can always look into page table for any VA to PA
translation. This approach will solve lot of complexity in makedumpfile. It
will in turn remove dependency over variables like VMALLOC_START,
MODULES_VADDR etc whose definition keeps changing in newer kernel version.

Moreover, I do not see any side effect of this approach in terms of
execution timing. I tested with IBM x3950 X6 machine having 4136359 MB of
memory. These are the results of makedumpfile execution time:

Without this patch:
===================
With -d 31:
Trial 1: 237.59526248 S
Trial 2: 235.236914962 S
Trail 3: 237.678712045 S

With -d 1:
Trial 1: 2548.905296877 S
Trial 2: 2549.759881756 S

With this patch:
===================
With -d 31:
Trial 1: 232.713841516 S
Trial 2: 228.45697177 S
Trail 3: 232.942262441 S

With -d 1:
Trial 1: 2768.424565806 S
Trial 2: 2749.622115455 S
Trail 3: 2537.770359073 S

Signed-off-by: Pratyush Anand <panand at redhat.com>
---
 arch/x86_64.c  | 42 ++++++++----------------------------------
 makedumpfile.h |  4 ++--
 2 files changed, 10 insertions(+), 36 deletions(-)

diff --git a/arch/x86_64.c b/arch/x86_64.c
index a96fd8ae00a1..fe2764a8bec2 100644
--- a/arch/x86_64.c
+++ b/arch/x86_64.c
@@ -203,6 +203,12 @@ vtop4_x86_64(unsigned long vaddr)
 {
 	unsigned long page_dir, pml4, pgd_paddr, pgd_pte, pmd_paddr, pmd_pte;
 	unsigned long pte_paddr, pte;
+	unsigned long phys_base;
+
+	if (SYMBOL(phys_base) != NOT_FOUND_SYMBOL)
+		phys_base = info->phys_base;
+	else
+		phys_base = 0;
 
 	if (SYMBOL(init_level4_pgt) == NOT_FOUND_SYMBOL) {
 		ERRMSG("Can't get the symbol of init_level4_pgt.\n");
@@ -212,9 +218,9 @@ vtop4_x86_64(unsigned long vaddr)
 	/*
 	 * Get PGD.
 	 */
-	page_dir  = SYMBOL(init_level4_pgt);
+	page_dir = SYMBOL(init_level4_pgt) - __START_KERNEL_map + phys_base;
 	page_dir += pml4_index(vaddr) * sizeof(unsigned long);
-	if (!readmem(VADDR, page_dir, &pml4, sizeof pml4)) {
+	if (!readmem(PADDR, page_dir, &pml4, sizeof pml4)) {
 		ERRMSG("Can't get pml4 (page_dir:%lx).\n", page_dir);
 		return NOT_PADDR;
 	}
@@ -285,38 +291,6 @@ vtop4_x86_64(unsigned long vaddr)
 	return (pte & ENTRY_MASK) + PAGEOFFSET(vaddr);
 }
 
-unsigned long long
-vaddr_to_paddr_x86_64(unsigned long vaddr)
-{
-	unsigned long phys_base;
-	unsigned long long paddr;
-
-	/*
-	 * Check the relocatable kernel.
-	 */
-	if (SYMBOL(phys_base) != NOT_FOUND_SYMBOL)
-		phys_base = info->phys_base;
-	else
-		phys_base = 0;
-
-	if (is_vmalloc_addr_x86_64(vaddr)) {
-		if ((paddr = vtop4_x86_64(vaddr)) == NOT_PADDR) {
-			ERRMSG("Can't convert a virtual address(%lx) to " \
-			    "physical address.\n", vaddr);
-			return NOT_PADDR;
-		}
-	} else if (vaddr >= __START_KERNEL_map) {
-		paddr = vaddr - __START_KERNEL_map + phys_base;
-
-	} else {
-		if (is_xen_memory())
-			paddr = vaddr - PAGE_OFFSET_XEN_DOM0;
-		else
-			paddr = vaddr - PAGE_OFFSET;
-	}
-	return paddr;
-}
-
 /*
  * for Xen extraction
  */
diff --git a/makedumpfile.h b/makedumpfile.h
index a5955ff750e5..13559651feb6 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -863,12 +863,12 @@ int is_vmalloc_addr_x86_64(ulong vaddr);
 int get_phys_base_x86_64(void);
 int get_machdep_info_x86_64(void);
 int get_versiondep_info_x86_64(void);
-unsigned long long vaddr_to_paddr_x86_64(unsigned long vaddr);
+unsigned long long vtop4_x86_64(unsigned long vaddr);
 #define find_vmemmap()		find_vmemmap_x86_64()
 #define get_phys_base()		get_phys_base_x86_64()
 #define get_machdep_info()	get_machdep_info_x86_64()
 #define get_versiondep_info()	get_versiondep_info_x86_64()
-#define vaddr_to_paddr(X)	vaddr_to_paddr_x86_64(X)
+#define vaddr_to_paddr(X)	vtop4_x86_64(X)
 #define is_phys_addr(X)		(!is_vmalloc_addr_x86_64(X))
 #endif /* x86_64 */
 
-- 
2.7.4