[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 5/6] x86/pagewalk: Improve the logic behind setting access and dirty bits
The boolean pse2M is misnamed, because it might refer to a 4M superpage. Switch the logic to be in terms of the level of the leaf entry, and rearrange the calls to set_ad_bits() to be a fallthrough switch statement, to make it easier to follow. Alter set_ad_bits() to take properly typed pointers and booleans rather than integers. Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> --- CC: Jan Beulich <JBeulich@xxxxxxxx> CC: Tim Deegan <tim@xxxxxxx> CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx> v3: * Pass properly-typed pointers. * Correct some comments * Drop redundant leaf_level == 1 check v2: * New --- xen/arch/x86/mm/guest_walk.c | 82 +++++++++++++++++++++++++------------------- 1 file changed, 47 insertions(+), 35 deletions(-) diff --git a/xen/arch/x86/mm/guest_walk.c b/xen/arch/x86/mm/guest_walk.c index e34a5ec..d57fb4d 100644 --- a/xen/arch/x86/mm/guest_walk.c +++ b/xen/arch/x86/mm/guest_walk.c @@ -32,24 +32,28 @@ asm(".file \"" __OBJECT_FILE__ "\""); #include <asm/page.h> #include <asm/guest_pt.h> -/* Modify a guest pagetable entry to set the Accessed and Dirty bits. - * Returns non-zero if it actually writes to guest memory. */ -static uint32_t set_ad_bits(void *guest_p, void *walk_p, int set_dirty) +/* + * Modify a guest pagetable entry to set the Accessed and Dirty bits. + * Returns true if it actually writes to guest memory. + */ +static bool set_ad_bits(guest_intpte_t *guest_p, guest_intpte_t *walk_p, + bool set_dirty) { - guest_intpte_t old, new; + guest_intpte_t new, old = *walk_p; - old = *(guest_intpte_t *)walk_p; new = old | _PAGE_ACCESSED | (set_dirty ? _PAGE_DIRTY : 0); - if ( old != new ) + if ( old != new ) { - /* Write the new entry into the walk, and try to write it back + /* + * Write the new entry into the walk, and try to write it back * into the guest table as well. If the guest table has changed - * under out feet then leave it alone. */ - *(guest_intpte_t *)walk_p = new; - if ( cmpxchg(((guest_intpte_t *)guest_p), old, new) == old ) - return 1; + * under our feet then leave it alone. + */ + *walk_p = new; + if ( cmpxchg(guest_p, old, new) == old ) + return true; } - return 0; + return false; } /* @@ -89,7 +93,7 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m, guest_l4e_t *l4p; #endif uint32_t gflags, rc; - bool_t pse1G = 0, pse2M = 0; + unsigned int leaf_level; p2m_query_t qt = P2M_ALLOC | P2M_UNSHARE; #define AR_ACCUM_AND (_PAGE_USER | _PAGE_RW) @@ -179,9 +183,7 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m, ar_and &= gflags; ar_or |= gflags; - pse1G = !!(gflags & _PAGE_PSE); - - if ( pse1G ) + if ( gflags & _PAGE_PSE ) { /* Generate a fake l1 table entry so callers don't all * have to understand superpages. */ @@ -204,6 +206,7 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m, ((va >> PAGE_SHIFT) & GUEST_L3_GFN_MASK)); gw->l1e = guest_l1e_from_gfn(start, flags); gw->l2mfn = gw->l1mfn = INVALID_MFN; + leaf_level = 3; goto leaf; } @@ -273,9 +276,7 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m, ar_and &= gflags; ar_or |= gflags; - pse2M = !!(gflags & _PAGE_PSE); - - if ( pse2M ) + if ( gflags & _PAGE_PSE ) { /* Special case: this guest VA is in a PSE superpage, so there's * no guest l1e. We make one up so that the propagation code @@ -309,6 +310,7 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m, gw->l1e = guest_l1e_from_gfn(start, flags); #endif gw->l1mfn = INVALID_MFN; + leaf_level = 2; goto leaf; } @@ -340,6 +342,8 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m, ar_and &= gflags; ar_or |= gflags; + leaf_level = 1; + leaf: gw->pfec |= PFEC_page_present; @@ -413,24 +417,32 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m, * success. Although the PRMs say higher-level _PAGE_ACCESSED bits * get set whenever a lower-level PT is used, at least some hardware * walkers behave this way. */ -#if GUEST_PAGING_LEVELS == 4 /* 64-bit only... */ - if ( set_ad_bits(l4p + guest_l4_table_offset(va), &gw->l4e, 0) ) - paging_mark_dirty(d, gw->l4mfn); - if ( set_ad_bits(l3p + guest_l3_table_offset(va), &gw->l3e, - (pse1G && (walk & PFEC_write_access))) ) - paging_mark_dirty(d, gw->l3mfn); -#endif - if ( !pse1G ) + switch ( leaf_level ) { - if ( set_ad_bits(l2p + guest_l2_table_offset(va), &gw->l2e, - (pse2M && (walk & PFEC_write_access))) ) + default: + ASSERT_UNREACHABLE(); + break; + + case 1: + if ( set_ad_bits(&l1p[guest_l1_table_offset(va)].l1, &gw->l1e.l1, + (walk & PFEC_write_access)) ) + paging_mark_dirty(d, gw->l1mfn); + /* Fallthrough */ + case 2: + if ( set_ad_bits(&l2p[guest_l2_table_offset(va)].l2, &gw->l2e.l2, + (walk & PFEC_write_access) && leaf_level == 2) ) paging_mark_dirty(d, gw->l2mfn); - if ( !pse2M ) - { - if ( set_ad_bits(l1p + guest_l1_table_offset(va), &gw->l1e, - (walk & PFEC_write_access)) ) - paging_mark_dirty(d, gw->l1mfn); - } + /* Fallthrough */ +#if GUEST_PAGING_LEVELS == 4 /* 64-bit only... */ + case 3: + if ( set_ad_bits(&l3p[guest_l3_table_offset(va)].l3, &gw->l3e.l3, + (walk & PFEC_write_access) && leaf_level == 3) ) + paging_mark_dirty(d, gw->l3mfn); + + if ( set_ad_bits(&l4p[guest_l4_table_offset(va)].l4, &gw->l4e.l4, + false) ) + paging_mark_dirty(d, gw->l4mfn); +#endif } out: -- 2.1.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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