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xen.23693
5c7561aa-x86-shadow-dont-use-map_domain_page_gl...
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File 5c7561aa-x86-shadow-dont-use-map_domain_page_global.patch of Package xen.23693
# Commit 43282a5e64da26fad544e0100abf35048cf65b46 # Date 2019-02-26 16:56:26 +0100 # Author Jan Beulich <jbeulich@suse.com> # Committer Jan Beulich <jbeulich@suse.com> x86/shadow: don't use map_domain_page_global() on paths that may not fail The assumption (according to one comment) and hope (according to another) that map_domain_page_global() can't fail are both wrong on large enough systems. Do away with the guest_vtable field altogether, and establish / tear down the desired mapping as necessary. The alternatives, discarded as being undesirable, would have been to either crash the guest in sh_update_cr3() when the mapping fails, or to bubble up an error indicator, which upper layers would have a hard time to deal with (other than again by crashing the guest). Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> Acked-by: Tim Deegan <tim@xen.org> --- a/xen/arch/x86/mm/shadow/multi.c +++ b/xen/arch/x86/mm/shadow/multi.c @@ -175,18 +175,22 @@ static inline bool sh_walk_guest_tables(struct vcpu *v, unsigned long va, walk_t *gw, uint32_t pfec) { - return guest_walk_tables(v, p2m_get_hostp2m(v->domain), va, gw, pfec, #if GUEST_PAGING_LEVELS == 3 /* PAE */ - INVALID_MFN, - v->arch.paging.shadow.gl3e + return guest_walk_tables(v, p2m_get_hostp2m(v->domain), va, gw, pfec, + INVALID_MFN, v->arch.paging.shadow.gl3e); #else /* 32 or 64 */ - (((v->arch.flags & TF_kernel_mode) || - is_pv_32bit_vcpu(v)) - ? pagetable_get_mfn(v->arch.guest_table) - : pagetable_get_mfn(v->arch.guest_table_user)), - v->arch.paging.shadow.guest_vtable + const struct domain *d = v->domain; + mfn_t root_mfn = ((v->arch.flags & TF_kernel_mode) || is_pv_32bit_domain(d) + ? pagetable_get_mfn(v->arch.guest_table) + : pagetable_get_mfn(v->arch.guest_table_user)); + void *root_map = map_domain_page(root_mfn); + bool ok = guest_walk_tables(v, p2m_get_hostp2m(d), va, gw, pfec, + root_mfn, root_map); + + unmap_domain_page(root_map); + + return ok; #endif - ); } /* This validation is called with lock held, and after write permission @@ -226,8 +230,9 @@ shadow_check_gwalk(struct vcpu *v, unsig perfc_incr(shadow_check_gwalk); #if GUEST_PAGING_LEVELS >= 3 /* PAE or 64... */ #if GUEST_PAGING_LEVELS >= 4 /* 64-bit only... */ - l4p = (guest_l4e_t *)v->arch.paging.shadow.guest_vtable; + l4p = map_domain_page(gw->l4mfn); mismatch |= (gw->l4e.l4 != l4p[guest_l4_table_offset(va)].l4); + unmap_domain_page(l4p); l3p = map_domain_page(gw->l3mfn); mismatch |= (gw->l3e.l3 != l3p[guest_l3_table_offset(va)].l3); unmap_domain_page(l3p); @@ -235,13 +240,11 @@ shadow_check_gwalk(struct vcpu *v, unsig mismatch |= (gw->l3e.l3 != v->arch.paging.shadow.gl3e[guest_l3_table_offset(va)].l3); #endif +#endif l2p = map_domain_page(gw->l2mfn); mismatch |= (gw->l2e.l2 != l2p[guest_l2_table_offset(va)].l2); unmap_domain_page(l2p); -#else - l2p = (guest_l2e_t *)v->arch.paging.shadow.guest_vtable; - mismatch |= (gw->l2e.l2 != l2p[guest_l2_table_offset(va)].l2); -#endif + if ( !(guest_can_use_l2_superpages(v) && (guest_l2e_get_flags(gw->l2e) & _PAGE_PSE)) ) { @@ -3887,7 +3890,8 @@ sh_update_linear_entries(struct vcpu *v) } -/* Removes vcpu->arch.paging.shadow.guest_vtable and vcpu->arch.shadow_table[]. +/* + * Removes vcpu->arch.shadow_table[]. * Does all appropriate management/bookkeeping/refcounting/etc... */ static void @@ -3898,23 +3902,6 @@ sh_detach_old_tables(struct vcpu *v) int i = 0; //// - //// vcpu->arch.paging.shadow.guest_vtable - //// - -#if GUEST_PAGING_LEVELS == 3 - /* PAE guests don't have a mapping of the guest top-level table */ - ASSERT(v->arch.paging.shadow.guest_vtable == NULL); -#else - if ( v->arch.paging.shadow.guest_vtable ) - { - if ( shadow_mode_external(d) || shadow_mode_translate(d) ) - unmap_domain_page_global(v->arch.paging.shadow.guest_vtable); - v->arch.paging.shadow.guest_vtable = NULL; - } -#endif // !NDEBUG - - - //// //// vcpu->arch.shadow_table[] //// @@ -4071,28 +4058,10 @@ sh_update_cr3(struct vcpu *v, int do_loc #endif gmfn = pagetable_get_mfn(v->arch.guest_table); - - //// - //// vcpu->arch.paging.shadow.guest_vtable - //// -#if GUEST_PAGING_LEVELS == 4 - if ( shadow_mode_external(d) || shadow_mode_translate(d) ) - { - if ( v->arch.paging.shadow.guest_vtable ) - unmap_domain_page_global(v->arch.paging.shadow.guest_vtable); - v->arch.paging.shadow.guest_vtable = map_domain_page_global(gmfn); - /* PAGING_LEVELS==4 implies 64-bit, which means that - * map_domain_page_global can't fail */ - BUG_ON(v->arch.paging.shadow.guest_vtable == NULL); - } - else - v->arch.paging.shadow.guest_vtable = __linear_l4_table; -#elif GUEST_PAGING_LEVELS == 3 +#if GUEST_PAGING_LEVELS == 3 /* On PAE guests we don't use a mapping of the guest's own top-level * table. We cache the current state of that table and shadow that, * until the next CR3 write makes us refresh our cache. */ - ASSERT(v->arch.paging.shadow.guest_vtable == NULL); - if ( shadow_mode_external(d) ) /* Find where in the page the l3 table is */ guest_idx = guest_index((void *)v->arch.hvm_vcpu.guest_cr[3]); @@ -4108,20 +4077,6 @@ sh_update_cr3(struct vcpu *v, int do_loc for ( i = 0; i < 4 ; i++ ) v->arch.paging.shadow.gl3e[i] = gl3e[i]; unmap_domain_page(gl3e); -#elif GUEST_PAGING_LEVELS == 2 - if ( shadow_mode_external(d) || shadow_mode_translate(d) ) - { - if ( v->arch.paging.shadow.guest_vtable ) - unmap_domain_page_global(v->arch.paging.shadow.guest_vtable); - v->arch.paging.shadow.guest_vtable = map_domain_page_global(gmfn); - /* Does this really need map_domain_page_global? Handle the - * error properly if so. */ - BUG_ON(v->arch.paging.shadow.guest_vtable == NULL); /* XXX */ - } - else - v->arch.paging.shadow.guest_vtable = __linear_l2_table; -#else -#error this should never happen #endif --- a/xen/include/asm-x86/domain.h +++ b/xen/include/asm-x86/domain.h @@ -135,8 +135,6 @@ struct shadow_vcpu { l3_pgentry_t l3table[4] __attribute__((__aligned__(32))); /* PAE guests: per-vcpu cache of the top-level *guest* entries */ l3_pgentry_t gl3e[4] __attribute__((__aligned__(32))); - /* Non-PAE guests: pointer to guest top-level pagetable */ - void *guest_vtable; /* Last MFN that we emulated a write to as unshadow heuristics. */ unsigned long last_emulated_mfn_for_unshadow; /* MFN of the last shadow that we shot a writeable mapping in */
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