[PATCH] x86/hap: Defer P2M TLB flushes

[Ross Lagerwall <ross.lagerwall@citrix.com>]

Like the EPT code, defer TLB flushes to reduce the number of flushes and
avoid holding the P2M lock while flushing. This can substantially
improve performance in some scenarios.

The cases where the TLB needs to be flushed without deferring are
already handled by the call to p2m_tlb_flush_sync() in p2m_free_ptp().

Suggested-by: Roger Pau Monne <roger.pau@citrix.com>
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
---
 xen/arch/x86/mm/hap/hap.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c
index a337752bf488..1eba995c7b39 100644
--- a/xen/arch/x86/mm/hap/hap.c
+++ b/xen/arch/x86/mm/hap/hap.c
@@ -813,16 +813,26 @@ static void cf_check hap_update_paging_modes(struct vcpu *v)
 
 static void cf_check
 hap_write_p2m_entry_post(struct p2m_domain *p2m, unsigned int oflags)
+{
+    if ( oflags & _PAGE_PRESENT )
+    {
+        ASSERT(p2m->defer_flush);
+        p2m->need_flush = true;
+    }
+}
+
+static void cf_check
+hap_p2m_tlb_flush(struct p2m_domain *p2m)
 {
     struct domain *d = p2m->domain;
 
-    if ( oflags & _PAGE_PRESENT )
-        guest_flush_tlb_mask(d, d->dirty_cpumask);
+    guest_flush_tlb_mask(d, d->dirty_cpumask);
 }
 
 void hap_p2m_init(struct p2m_domain *p2m)
 {
     p2m->write_p2m_entry_post = hap_write_p2m_entry_post;
+    p2m->tlb_flush = hap_p2m_tlb_flush;
 }
 
 static unsigned long cf_check hap_gva_to_gfn_real_mode(
-- 
2.53.0