From: Tim Deegan Date: Fri, 18 Aug 2017 14:23:44 +0000 (+0100) Subject: xen/x86/shadow: adjust barriers around gtable_dirty_version. X-Git-Tag: archive/raspbian/4.11.1-1+rpi1~1^2~66^2~1637 X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https://%22%22/%22http:/www.example.com/cgi/%22https:/%22%22?a=commitdiff_plain;h=82d510c88dc12c8aa31aa97bab633b922737bdf4;p=xen.git xen/x86/shadow: adjust barriers around gtable_dirty_version. Use the smp_ variants, as we're only synchronizing against other CPUs. Add a write barrier before incrementing the version. x86's memory ordering rules and the presence of various out-of-unit function calls mean that this code worked OK before, and the barriers are mostly decorative. Signed-off-by: Tim Deegan Reviewed-by: Andrew Cooper --- diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c index c9c2252746..f8a89287ca 100644 --- a/xen/arch/x86/mm/shadow/multi.c +++ b/xen/arch/x86/mm/shadow/multi.c @@ -206,6 +206,7 @@ shadow_check_gwalk(struct vcpu *v, unsigned long va, walk_t *gw, int version) ASSERT(paging_locked_by_me(d)); + /* No need for smp_rmb() here; taking the paging lock was enough. */ if ( version == atomic_read(&d->arch.paging.shadow.gtable_dirty_version) ) return 1; @@ -3112,7 +3113,7 @@ static int sh_page_fault(struct vcpu *v, * will make sure no inconsistent mapping being translated into * shadow page table. */ version = atomic_read(&d->arch.paging.shadow.gtable_dirty_version); - rmb(); + smp_rmb(); walk_ok = sh_walk_guest_tables(v, va, &gw, error_code); #if (SHADOW_OPTIMIZATIONS & SHOPT_OUT_OF_SYNC) @@ -3188,6 +3189,7 @@ static int sh_page_fault(struct vcpu *v, * overlapping with this one may be inconsistent */ perfc_incr(shadow_rm_write_flush_tlb); + smp_wmb(); atomic_inc(&d->arch.paging.shadow.gtable_dirty_version); flush_tlb_mask(d->domain_dirty_cpumask); }