[xen staging] x86/hap: Defer NPT P2M TLB flushes

[patchbot@xxxxxxx]

commit e1604ea8270096e5bb15866a1db75fbe56a730c7
Author:     Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
AuthorDate: Mon Mar 23 11:17:06 2026 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Mar 23 11:17:06 2026 +0100

    x86/hap: Defer NPT P2M TLB flushes
    
    Like the EPT code, defer TLB flushes for NPT 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@xxxxxxxxxx>
    Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/mm/hap/hap.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c
index a337752bf4..5ccb80bda5 100644
--- a/xen/arch/x86/mm/hap/hap.c
+++ b/xen/arch/x86/mm/hap/hap.c
@@ -814,15 +814,33 @@ 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)
 {
-    struct domain *d = p2m->domain;
+    if ( !(oflags & _PAGE_PRESENT) )
+        return;
+
+    if ( unlikely(!p2m->defer_flush) )
+    {
+        const struct domain *d = p2m->domain;
 
-    if ( oflags & _PAGE_PRESENT )
+        ASSERT_UNREACHABLE();
         guest_flush_tlb_mask(d, d->dirty_cpumask);
+        return;
+    }
+
+    p2m->need_flush = true;
+}
+
+static void cf_check
+hap_p2m_tlb_flush(struct p2m_domain *p2m)
+{
+    const struct domain *d = p2m->domain;
+
+    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(
--
generated by git-patchbot for /home/xen/git/xen.git#staging