From a7ab52f9e87c5140b8f0c5444c79d061a6985a2b Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Wed, 18 Nov 2020 12:34:54 +0100 Subject: [PATCH] x86/HAP: move nested-P2M flush calculations out of locked region MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit By latching the old MFN into a local variable, these calculations don't depend on anything but local variables anymore. Hence the point in time when they get performed doesn't matter anymore, so they can be moved past the locked region. Signed-off-by: Jan Beulich Acked-by: Roger Pau Monné --- xen/arch/x86/mm/hap/hap.c | 25 +++++++++++-------------- 1 file changed, 11 insertions(+), 14 deletions(-) diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c index 69b06f19b5..d1ad10003c 100644 --- a/xen/arch/x86/mm/hap/hap.c +++ b/xen/arch/x86/mm/hap/hap.c @@ -780,7 +780,7 @@ hap_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn, l1_pgentry_t *p, { struct domain *d = p2m->domain; uint32_t old_flags; - bool_t flush_nestedp2m = 0; + mfn_t omfn; int rc; /* We know always use the host p2m here, regardless if the vcpu @@ -790,21 +790,11 @@ hap_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn, l1_pgentry_t *p, paging_lock(d); old_flags = l1e_get_flags(*p); - - if ( nestedhvm_enabled(d) && (old_flags & _PAGE_PRESENT) - && !p2m_get_hostp2m(d)->defer_nested_flush ) { - /* We are replacing a valid entry so we need to flush nested p2ms, - * unless the only change is an increase in access rights. */ - mfn_t omfn = l1e_get_mfn(*p); - mfn_t nmfn = l1e_get_mfn(new); - - flush_nestedp2m = !(mfn_eq(omfn, nmfn) - && perms_strictly_increased(old_flags, l1e_get_flags(new)) ); - } + omfn = l1e_get_mfn(*p); rc = p2m_entry_modify(p2m, p2m_flags_to_type(l1e_get_flags(new)), p2m_flags_to_type(old_flags), l1e_get_mfn(new), - l1e_get_mfn(*p), level); + omfn, level); if ( rc ) { paging_unlock(d); @@ -817,7 +807,14 @@ hap_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn, l1_pgentry_t *p, paging_unlock(d); - if ( flush_nestedp2m ) + if ( nestedhvm_enabled(d) && (old_flags & _PAGE_PRESENT) && + !p2m_get_hostp2m(d)->defer_nested_flush && + /* + * We are replacing a valid entry so we need to flush nested p2ms, + * unless the only change is an increase in access rights. + */ + (!mfn_eq(omfn, l1e_get_mfn(new)) || + !perms_strictly_increased(old_flags, l1e_get_flags(new))) ) p2m_flush_nestedp2m(d); return 0; -- 2.30.2