makedumpfile: Support for x86_64 1G pages
Subsystems (2)
PATCH 1/1 makedumpfile: Support for x86_64 1G pages
The PS bit is not recognized in the Page-Directory-Pointer Table (pgdir in Linux terms), so virtual addresses that map to a 1G page will be translated incorrectly.
This bug affects both Xen and bare metal. I don't think it can be easily triggered in practice, because 1G mappings are created only for:
1. direct 1:1 mapping of physical memory, for which we don't walk the page tables, but instead subtract the corresponding virtual offset, and
2. 1G hugepages, which are only used for userspace data.
Anyway, if we ever happen to hit a 1G page now, the virtual address will be translated correctly.
While fixing this, I consolidated the vtop() translation routines and changed some of the constants. The basic idea is that the format of a page table entry is defined by the architecture, so we can use hard-coded constants everywhere.
I also always mask off reserved bits, because they might get defined in a later revision of the specification.
--- arch/x86_64.c | 33 +++++++++++++++++++-------------- makedumpfile.h | 21 +++++++++++++-------- 2 files changed, 32 insertions(+), 22 deletions(-)
arch/x86_64.c +19 -14
@@ -211,7 +211,7 @@ vtop4_x86_64(unsigned long vaddr)/* * Get PUD. */ - pgd_paddr = pml4 &PHYSICAL_PAGE_MASK ; + pgd_paddr = pml4 &ENTRY_MASK ; pgd_paddr +=pgd_index (vaddr) *sizeof (unsigned long );if (!readmem (PADDR , pgd_paddr, &pgd_pte,sizeof pgd_pte)) {ERRMSG ("Can't get pgd_pte (pgd_paddr:%lx).\n" , pgd_paddr);
@@ -224,11 +224,14 @@ vtop4_x86_64(unsigned long vaddr)ERRMSG ("Can't get a valid pgd_pte.\n" );return NOT_PADDR ; } +if (pgd_pte & _PAGE_PSE)/* 1GB pages */ +return (pgd_pte &ENTRY_MASK &PGDIR_MASK ) + + (vaddr & ~PGDIR_MASK );/* * Get PMD. */ - pmd_paddr = pgd_pte &PHYSICAL_PAGE_MASK ; + pmd_paddr = pgd_pte &ENTRY_MASK ; pmd_paddr +=pmd_index (vaddr) *sizeof (unsigned long );if (!readmem (PADDR , pmd_paddr, &pmd_pte,sizeof pmd_pte)) {ERRMSG ("Can't get pmd_pte (pmd_paddr:%lx).\n" , pmd_paddr);
@@ -241,14 +244,14 @@ vtop4_x86_64(unsigned long vaddr)ERRMSG ("Can't get a valid pmd_pte.\n" );return NOT_PADDR ; } -if (pmd_pte & _PAGE_PSE) -return (PAGEBASE (pmd_pte) &PHYSICAL_PAGE_MASK ) - + (vaddr & ~_2MB_PAGE_MASK); +if (pmd_pte & _PAGE_PSE)/* 2MB pages */ +return (pmd_pte &ENTRY_MASK &PMD_MASK ) + + (vaddr & ~PMD_MASK );/* * Get PTE. */ - pte_paddr = pmd_pte &PHYSICAL_PAGE_MASK ; + pte_paddr = pmd_pte &ENTRY_MASK ; pte_paddr +=pte_index (vaddr) *sizeof (unsigned long );if (!readmem (PADDR , pte_paddr, &pte,sizeof pte)) {ERRMSG ("Can't get pte (pte_paddr:%lx).\n" , pte_paddr);
@@ -261,7 +264,7 @@ vtop4_x86_64(unsigned long vaddr)ERRMSG ("Can't get a valid pte.\n" );return NOT_PADDR ; } -return (PAGEBASE (pte) &PHYSICAL_PAGE_MASK ) +PAGEOFFSET (vaddr); +return (pte &ENTRY_MASK ) +PAGEOFFSET (vaddr); }unsigned long long
@@ -330,6 +333,10 @@ kvtop_xen_x86_64(unsigned long kvaddr)if (!(entry & _PAGE_PRESENT))return NOT_PADDR ; +if (entry & _PAGE_PSE)/* 1GB pages */ +return (entry &ENTRY_MASK &PGDIR_MASK ) + + (kvaddr & ~PGDIR_MASK ); + dirp = entry &ENTRY_MASK ; dirp +=pmd_index (kvaddr) *sizeof (unsigned long long );if (!readmem (MADDR_XEN , dirp, &entry,sizeof (entry)))
@@ -338,10 +345,10 @@ kvtop_xen_x86_64(unsigned long kvaddr)if (!(entry & _PAGE_PRESENT))return NOT_PADDR ; -if (entry & _PAGE_PSE) { - entry = (entry &ENTRY_MASK ) + (kvaddr & ((1UL <<PMD_SHIFT ) -1 )); -return entry; - } +if (entry & _PAGE_PSE)/* 2MB pages */ +return (entry &ENTRY_MASK &PMD_MASK ) + + (kvaddr & ~PMD_MASK ); + dirp = entry &ENTRY_MASK ; dirp +=pte_index (kvaddr) *sizeof (unsigned long long );if (!readmem (MADDR_XEN , dirp, &entry,sizeof (entry)))
@@ -351,9 +358,7 @@ kvtop_xen_x86_64(unsigned long kvaddr)return NOT_PADDR ; } - entry = (entry &ENTRY_MASK ) + (kvaddr & ((1UL <<PTE_SHIFT ) -1 )); - -return entry; +return (entry &ENTRY_MASK ) +PAGEOFFSET (kvaddr); }int get_xen_basic_info_x86_64 (void )
makedumpfile.h +8 -7
@@ -143,7 +143,6 @@ isAnon(unsigned long mapping)#define PAGESHIFT () (info->page_shift)#define PAGEOFFSET (X ) (((unsigned long)(X)) & (PAGESIZE() - 1))#define PAGEBASE (X ) (((unsigned long)(X)) & ~(PAGESIZE() - 1)) -#define _2MB_PAGE_MASK (~((2*1048576)-1))/* * for SPARSEMEM
@@ -494,7 +493,10 @@ do { \#define _PAGE_PRESENT (0x001)#define _PAGE_PSE (0x080) -#define ENTRY_MASK (~0x8000000000000fffULL) +/* Physical addresses are up to 52 bits (AMD64). +* Mask off bits 52-62 (reserved) and bit 63 (NX). +*/ +#define ENTRY_MASK (~0xfff0000000000fffULL)#endif /* x86 */
@@ -527,8 +529,12 @@ do { \#define PML4_SHIFT (39)#define PTRS_PER_PML4 (512)#define PGDIR_SHIFT (30) +#define PGDIR_SIZE (1UL << PGDIR_SHIFT) +#define PGDIR_MASK (~(PGDIR_SIZE - 1))#define PTRS_PER_PGD (512)#define PMD_SHIFT (21) +#define PMD_SIZE (1UL << PMD_SHIFT) +#define PMD_MASK (~(PMD_SIZE - 1))#define PTRS_PER_PMD (512)#define PTRS_PER_PTE (512)#define PTE_SHIFT (12)
@@ -539,11 +545,7 @@ do { \#define pte_index (address) (((address) >> PTE_SHIFT) & (PTRS_PER_PTE - 1))#define _PAGE_PRESENT (0x001) -#define _PAGE_PSE (0x080)/* 2MB page */ - -#define __PHYSICAL_MASK_SHIFT (40) -#define __PHYSICAL_MASK ((1UL << __PHYSICAL_MASK_SHIFT) - 1) -#define PHYSICAL_PAGE_MASK (~(PAGESIZE()-1) & (__PHYSICAL_MASK <<
PAGESHIFT()))
+#define _PAGE_PSE (0x080) /* 2MB or 1GB page */
#endif /* x86_64 */
@@ -1379,7 +1381,10 @@ int get_xen_info_x86(void);
#ifdef __x86_64__
-#define ENTRY_MASK (~0x8000000000000fffULL)
+/* The architectural limit for physical addresses is 52 bits.
+ * Mask off bits 52-62 (available for OS use) and bit 63 (NX).
+ */
+#define ENTRY_MASK (~0xfff0000000000fffULL)
#define MAX_X86_64_FRAMES (info->page_size / sizeof(unsigned long))
#define PAGE_OFFSET_XEN_DOM0 (0xffff880000000000) /* different from linux */
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Quoted 12 lines
-----Original Message-----
From: Petr Tesarik [mailto:[email protected]]
Sent: Tuesday, August 28, 2012 5:11 PM
To: [email protected]
Cc: Trapp, Norbert
Subject: [PATCH] makedumpfile: Support forx86_641G pagesThe PS bit is not recognized in the Page-Directory-Pointer Table (pgdir in Linux terms), so virtual addresses that map to a 1G page will be translated incorrectly.
Quoted 6 lines
This bug affects both Xen and bare metal. I don't think it can be easily triggered in practice, because 1G mappings are created only for:
1. direct 1:1 mapping of physical memory, for which we don't walk the page tables, but instead subtract the corresponding virtual offset, and
2. 1G hugepages, which are only used for userspace data.
...
Hello again,
With Xen not only the Linux kernel has to be considered, but the Xen hypervisor, too. The usage of 1 GB pages by the hypervisor is relevant for machines with recent types of processors and more than a small amount of memory.
With kind reagards
Norbert
Norbert Trapp
PBG PDG ES&S SWE OS 6
FUJITSU
Fujitsu Technology Solutions GmbH
Domagkstraße 28, D-80807 München, Germany
E-mail: [email protected]
Web: ts.fujitsu.com
Company details: ts.fujitsu.com/imprint
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