On Wed, Mar 28, 2007 at 06:46:40AM +1000, Herbert Xu wrote:

Here is a completely untested patch that demonstrates how this could be done on x86.

Cheers,

-- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <herb...@gondor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

-- diff -r 3ac19fda0bc2 xen/arch/x86/mm.c --- a/xen/arch/x86/mm.c Fri Mar 02 12:11:52 2007 +0000 +++ b/xen/arch/x86/mm.c Wed Mar 28 22:58:45 2007 +1000 @@ -1262,6 +1262,36 @@ static void free_l4_table(struct page_in #endif

+static inline int cmpxchg_intpte(intpte_t *p, + intpte_t *old, + intpte_t new, + unsigned long mfn, + struct vcpu *v) +{ + int rv; + + for ( ; ; ) + { + intpte_t t = *old; + + rv = paging_cmpxchg_guest_entry(v, p, old, new, _mfn(mfn)); + if ( unlikely(rv == 0) ) + { + MEM_LOG("Failed to update %" PRIpte " -> %" PRIpte + ": saw %" PRIpte, t, new, t); + break; + } + + if ( t == *old ) + break; + + /* Allowed to change in Accessed/Dirty flags only. */ + BUG_ON((t ^ *old) & ~(intpte_t)(_PAGE_ACCESSED|_PAGE_DIRTY)); + } + + return rv; +} + /* How to write an entry to the guest pagetables. * Returns 0 for failure (pointer not valid), 1 for success. */ static inline int update_intpte(intpte_t *p, @@ -1274,27 +1304,7 @@ static inline int update_intpte(intpte_t #ifndef PTE_UPDATE_WITH_CMPXCHG rv = paging_write_guest_entry(v, p, new, _mfn(mfn)); #else - { - intpte_t t = old; - for ( ; ; ) - { - rv = paging_cmpxchg_guest_entry(v, p, &t, new, _mfn(mfn)); - if ( unlikely(rv == 0) ) - { - MEM_LOG("Failed to update %" PRIpte " -> %" PRIpte - ": saw %" PRIpte, old, new, t); - break; - } - - if ( t == old ) - break; - - /* Allowed to change in Accessed/Dirty flags only. */ - BUG_ON((t ^ old) & ~(intpte_t)(_PAGE_ACCESSED|_PAGE_DIRTY)); - - old = t; - } - } + rv = cmpxchg_intpte(p, &old, new, mfn, v); #endif return rv; } @@ -2598,6 +2608,7 @@ static int destroy_grant_va_mapping( unsigned long addr, unsigned long frame, struct vcpu *v) { l1_pgentry_t *pl1e, ol1e; + intpte_t *ptep, opte, npte; unsigned long gl1mfn; int rc = 0;

@@ -2619,12 +2630,19 @@ static int destroy_grant_va_mapping( }

/* Delete pagetable entry. */ - if ( unlikely(!UPDATE_ENTRY(l1, pl1e, ol1e, l1e_empty(), gl1mfn, v)) ) + ptep = (intpte_t *)pl1e; + opte = l1e_get_intpte(ol1e); + npte = l1e_get_intpte(l1e_empty()); + + if ( unlikely(!cmpxchg_intpte(ptep, opte, npte, mfn, v)) ) { MEM_LOG("Cannot delete PTE entry at %p", (unsigned long *)pl1e); rc = GNTST_general_error; goto out; } + + if (!(opte & (intpte_t)_PAGE_ACCESSED)) + rc = GNTST_unused;

out: guest_unmap_l1e(v, pl1e); diff -r 3ac19fda0bc2 xen/common/grant_table.c --- a/xen/common/grant_table.c Fri Mar 02 12:11:52 2007 +0000 +++ b/xen/common/grant_table.c Wed Mar 28 22:58:45 2007 +1000 @@ -394,7 +394,7 @@ gnttab_map_grant_ref( return 0; }

-static void +static int __gnttab_unmap_grant_ref( struct gnttab_unmap_grant_ref *op) { @@ -416,7 +416,7 @@ __gnttab_unmap_grant_ref( { gdprintk(XENLOG_INFO, "Bad handle (%d).\n", op->handle); op->status = GNTST_bad_handle; - return; + return 0; }

map = &maptrack_entry(ld->grant_table, op->handle); @@ -425,7 +425,7 @@ __gnttab_unmap_grant_ref( { gdprintk(XENLOG_INFO, "Zero flags for handle (%d).\n", op->handle); op->status = GNTST_bad_handle; - return; + return 0; }

dom = map->domid; @@ -437,7 +437,7 @@ __gnttab_unmap_grant_ref( /* This can happen when a grant is implicitly unmapped. */ gdprintk(XENLOG_INFO, "Could not find domain %d\n", dom); domain_crash(ld); /* naughty... */ - return; + return 0; }

TRACE_1D(TRC_MEM_PAGE_GRANT_UNMAP, dom); @@ -511,9 +511,17 @@ __gnttab_unmap_grant_ref( gnttab_clear_flag(_GTF_reading, &sha->flags);

unmap_out: - op->status = rc; spin_unlock(&rd->grant_table->lock); rcu_unlock_domain(rd); + + op->status = rc; + + if (rc == GNTST_unused) { + op->status = GNTST_okay; + return 0; + } + + return 1; }

static long @@ -521,23 +529,25 @@ gnttab_unmap_grant_ref( XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t) uop, unsigned int count) { int i; + int used = 0; + int err = -EFAULT; struct gnttab_unmap_grant_ref op;

for ( i = 0; i < count; i++ ) { if ( unlikely(__copy_from_guest_offset(&op, uop, i, 1)) ) goto fault; - __gnttab_unmap_grant_ref(&op); + used |= __gnttab_unmap_grant_ref(&op); if ( unlikely(__copy_to_guest_offset(uop, i, &op, 1)) ) goto fault; }

- flush_tlb_mask(current->domain->domain_dirty_cpumask); - return 0; + err = 0;

fault: - flush_tlb_mask(current->domain->domain_dirty_cpumask); - return -EFAULT; + if (used) + flush_tlb_mask(current->domain->domain_dirty_cpumask); + return err; }

int diff -r 3ac19fda0bc2 xen/include/public/grant_table.h --- a/xen/include/public/grant_table.h Fri Mar 02 12:11:52 2007 +0000 +++ b/xen/include/public/grant_table.h Wed Mar 28 22:58:45 2007 +1000 @@ -360,6 +360,7 @@ DEFINE_XEN_GUEST_HANDLE(gnttab_query_siz /* * Values for error status returns. All errors are -ve. */ +#define GNTST_unused (1) /* Entry is unused (internal status). */ #define GNTST_okay (0) /* Normal return. */ #define GNTST_general_error (-1) /* General undefined error. */ #define GNTST_bad_domain (-2) /* Unrecognsed domain id. */