Xen project Mailing List

Re: [Xen-devel] [RESEND] Question about recursive mappings

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>

From: Mathieu Ropert <mro@xxxxxxxxxx>

Date: Fri, 26 May 2006 11:27:08 +0200

Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx

Delivery-date: Tue, 30 May 2006 09:06:21 -0700

List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Keir Fraser wrote:


On 24 May 2006, at 21:12, Mathieu Ropert wrote:

Ok, i've done a little patch which seems to resolve the issue on mytest setup. Basically, i've modified get_linear_pagetable(), added alevel parameter and call it for each level but level 1.I need to do a little more test before i post the patch. As tomorrowis a national day, it should be ready friday.

Can you try creating some mutually recursive pagetables (i.e., onelinearly maps the other, and vice versa) and then try 'xm destroy'ingthe domain?


 -- Keir

Here's the patch that solves my issue. I've only tested it for x86_64,

so any feedback on x86/PAE would be appreciated.

Tried to make mutually recursive tables and destroy the domain as you

suggested, no problem encountered.

Note that the union i used may seem a bit overkill, but i didn't saw any

other way to make it generic (even if brutal casting should work on any

x86/x86_64 arch).

Applies to cset 10166. Mathieu Signed-off-by: Mathieu Ropert <mro@xxxxxxxxxx>

diff -u -r a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c --- a/xen/arch/x86/mm.c 2006-05-26 11:05:08.000000000 +0200 +++ b/xen/arch/x86/mm.c 2006-05-26 11:14:33.000000000 +0200 @@ -415,7 +415,7 @@ */ static int get_linear_pagetable( - root_pgentry_t re, unsigned long re_pfn, struct domain *d) + pgentry_t re, unsigned long re_pfn, struct domain *d, int level) { unsigned long x, y; struct page_info *page; @@ -423,13 +423,13 @@ ASSERT( !shadow_mode_refcounts(d) ); - if ( (root_get_flags(re) & _PAGE_RW) ) + if ( (pgentry_get_flags(re, level) & _PAGE_RW) ) { MEM_LOG("Attempt to create linear p.t. with write perms"); return 0; } - if ( (pfn = root_get_pfn(re)) != re_pfn ) + if ( (pfn = pgentry_get_pfn(re, level)) != re_pfn ) { /* Make sure the mapped frame belongs to the correct domain. */ if ( unlikely(!get_page_from_pagenr(pfn, d)) ) @@ -444,8 +444,7 @@ do { x = y; if ( unlikely((x & PGT_count_mask) == PGT_count_mask) || - unlikely((x & (PGT_type_mask|PGT_validated)) != - (PGT_root_page_table|PGT_validated)) ) + unlikely(!(x & PGT_validated) || !is_ptp(x))) { put_page(page); return 0; @@ -532,9 +531,12 @@ vaddr <<= PGT_va_shift; rc = get_page_and_type_from_pagenr( l2e_get_pfn(l2e), PGT_l1_page_table | vaddr, d); -#if CONFIG_PAGING_LEVELS == 2 - if ( unlikely(!rc) ) - rc = get_linear_pagetable(l2e, pfn, d); +#if CONFIG_PAGING_LEVELS >= 2 + if ( unlikely(!rc) ) { + pgentry_t re; + re.l2.l2 = l2e.l2; + rc = get_linear_pagetable(re, pfn, d, 2); + } #endif return rc; } @@ -564,9 +566,12 @@ rc = get_page_and_type_from_pagenr( l3e_get_pfn(l3e), PGT_l2_page_table | vaddr, d); -#if CONFIG_PAGING_LEVELS == 3 - if ( unlikely(!rc) ) - rc = get_linear_pagetable(l3e, pfn, d); +#if CONFIG_PAGING_LEVELS >= 3 + if ( unlikely(!rc) ) { + pgentry_t re; + re.l3.l3 = l3e.l3; + rc = get_linear_pagetable(re, pfn, d, 3); + } #endif return rc; } @@ -597,8 +602,11 @@ l4e_get_pfn(l4e), PGT_l3_page_table | vaddr, d); - if ( unlikely(!rc) ) - rc = get_linear_pagetable(l4e, pfn, d); + if ( unlikely(!rc) ) { + pgentry_t re; + re.l4.l4 = l4e.l4; + rc = get_linear_pagetable(re, pfn, d, 4); + } return rc; } diff -u -r a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h --- a/xen/include/asm-x86/page.h 2006-05-26 11:05:09.000000000 +0200 +++ b/xen/include/asm-x86/page.h 2006-05-24 12:49:42.000000000 +0200 @@ -176,6 +176,67 @@ #define pagetable_get_pfn(x) ((x).pfn) #define mk_pagetable(pa) \ ({ pagetable_t __p; __p.pfn = (pa) >> PAGE_SHIFT; __p; }) + +typedef union { + l1_pgentry_t l1; +#if CONFIG_PAGING_LEVELS >= 2 + l2_pgentry_t l2; +#if CONFIG_PAGING_LEVELS >= 3 + l3_pgentry_t l3; +#if CONFIG_PAGING_LEVELS == 4 + l4_pgentry_t l4; +#endif /* LEVELS == 4 */ +#endif /* LEVELS >= 3 */ +#endif /* LEVELS >= 2 */ +} pgentry_t; + +static inline intpte_t pgentry_get_flags(pgentry_t p, int level) +{ + switch (level) + { + case 1: + return l1e_get_flags(p.l1); +#if CONFIG_PAGING_LEVELS >= 2 + case 2: + return l2e_get_flags(p.l2); +#if CONFIG_PAGING_LEVELS >= 3 + case 3: + return l3e_get_flags(p.l3); +#if CONFIG_PAGING_LEVELS == 4 + case 4: + return l4e_get_flags(p.l4); +#endif /* LEVELS == 4 */ +#endif /* LEVELS >= 3 */ +#endif /* LEVELS >= 2 */ + default: + /* should not happen */ + return 0; + } +} + +static inline intpte_t pgentry_get_pfn(pgentry_t p, int level) +{ + switch (level) + { + case 1: + return l1e_get_pfn(p.l1); +#if CONFIG_PAGING_LEVELS >= 2 + case 2: + return l2e_get_pfn(p.l2); +#if CONFIG_PAGING_LEVELS >= 3 + case 3: + return l3e_get_pfn(p.l3); +#if CONFIG_PAGING_LEVELS == 4 + case 4: + return l4e_get_pfn(p.l4); +#endif /* LEVELS == 4 */ +#endif /* LEVELS >= 3 */ +#endif /* LEVELS >= 2 */ + default: + /* should not happen */ + return 0; + } +} #endif #define clear_page(_p) memset((void *)(_p), 0, PAGE_SIZE) diff -u -r a/xen/include/asm-x86/x86_32/page-2level.h b/xen/include/asm-x86/x86_32/page-2level.h --- a/xen/include/asm-x86/x86_32/page-2level.h 2006-05-26 11:05:09.000000000 +0200 +++ b/xen/include/asm-x86/x86_32/page-2level.h 2006-05-26 11:09:56.000000000 +0200 @@ -28,6 +28,11 @@ #endif /* !__ASSEMBLY__ */ +/* Check if page type is page table (any level) */ +#define is_ptp(x) \ + ((x & PGT_type_mask) == PGT_l1_page_table \ + || (x & PGT_type_mask) == PGT_l2_page_table) + /* root table */ #define root_get_pfn l2e_get_pfn #define root_get_flags l2e_get_flags diff -u -r a/xen/include/asm-x86/x86_32/page-3level.h b/xen/include/asm-x86/x86_32/page-3level.h --- a/xen/include/asm-x86/x86_32/page-3level.h 2006-05-26 11:05:09.000000000 +0200 +++ b/xen/include/asm-x86/x86_32/page-3level.h 2006-05-26 11:10:47.000000000 +0200 @@ -38,6 +38,12 @@ #endif /* !__ASSEMBLY__ */ +/* Check if page type is page table (any level) */ +#define is_ptp(x) \ + ((x & PGT_type_mask) == PGT_l1_page_table \ + || (x & PGT_type_mask) == PGT_l2_page_table \ + || (x & PGT_type_mask) == PGT_l3_page_table) + /* root table */ #define root_get_pfn l3e_get_pfn #define root_get_flags l3e_get_flags diff -u -r a/xen/include/asm-x86/x86_64/page.h b/xen/include/asm-x86/x86_64/page.h --- a/xen/include/asm-x86/x86_64/page.h 2006-05-26 11:05:09.000000000 +0200 +++ b/xen/include/asm-x86/x86_64/page.h 2006-05-26 11:07:46.000000000 +0200 @@ -41,6 +41,13 @@ #endif /* !__ASSEMBLY__ */ +/* Check if page type is page table (any level) */ +#define is_ptp(x) \ + ((x & PGT_type_mask) == PGT_l1_page_table \ + || (x & PGT_type_mask) == PGT_l2_page_table \ + || (x & PGT_type_mask) == PGT_l3_page_table \ + || (x & PGT_type_mask) == PGT_l4_page_table) + /* Given a virtual address, get an entry offset into a linear page table. */ #define l1_linear_offset(_a) (((_a) & VADDR_MASK) >> L1_PAGETABLE_SHIFT) #define l2_linear_offset(_a) (((_a) & VADDR_MASK) >> L2_PAGETABLE_SHIFT)

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