[xen staging] xen/smp: Support NULL IPI function pointers

[patchbot@xxxxxxx]

commit 06c30ad7662f0c9fc8bc1c356f8aeaa63fb731ec
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Nov 17 16:16:23 2021 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Mon Nov 29 13:53:05 2021 +0000

    xen/smp: Support NULL IPI function pointers
    
    There are several cases where the act of interrupting a remote processor has
    the required side effect.  Explicitly allow NULL function pointers so the
    calling code doesn't have to provide a stub implementation.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/mm/hap/hap.c | 11 +----------
 xen/arch/x86/mm/p2m-ept.c | 11 ++---------
 xen/common/smp.c          |  6 +++++-
 3 files changed, 8 insertions(+), 20 deletions(-)

diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c
index 73575deb0d..5b269ef8b3 100644
--- a/xen/arch/x86/mm/hap/hap.c
+++ b/xen/arch/x86/mm/hap/hap.c
@@ -696,15 +696,6 @@ static void hap_update_cr3(struct vcpu *v, int do_locking, 
bool noflush)
     hvm_update_guest_cr3(v, noflush);
 }
 
-/*
- * Dummy function to use with on_selected_cpus in order to trigger a vmexit on
- * selected pCPUs. When the VM resumes execution it will get a new ASID/VPID
- * and thus a clean TLB.
- */
-static void dummy_flush(void *data)
-{
-}
-
 static bool flush_tlb(bool (*flush_vcpu)(void *ctxt, struct vcpu *v),
                       void *ctxt)
 {
@@ -737,7 +728,7 @@ static bool flush_tlb(bool (*flush_vcpu)(void *ctxt, struct 
vcpu *v),
      * not currently running will already be flushed when scheduled because of
      * the ASID tickle done in the loop above.
      */
-    on_selected_cpus(mask, dummy_flush, NULL, 0);
+    on_selected_cpus(mask, NULL, NULL, 0);
 
     return true;
 }
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index b2d57a3ee8..1459f66c00 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -1236,14 +1236,6 @@ static void ept_memory_type_changed(struct p2m_domain 
*p2m)
         ept_sync_domain(p2m);
 }
 
-static void __ept_sync_domain(void *info)
-{
-    /*
-     * The invalidation will be done before VMENTER (see
-     * vmx_vmenter_helper()).
-     */
-}
-
 static void ept_sync_domain_prepare(struct p2m_domain *p2m)
 {
     struct domain *d = p2m->domain;
@@ -1269,7 +1261,8 @@ static void ept_sync_domain_prepare(struct p2m_domain 
*p2m)
 
 static void ept_sync_domain_mask(struct p2m_domain *p2m, const cpumask_t *mask)
 {
-    on_selected_cpus(mask, __ept_sync_domain, p2m, 1);
+    /* Invalidation will be done in vmx_vmenter_helper(). */
+    on_selected_cpus(mask, NULL, NULL, 1);
 }
 
 void ept_sync_domain(struct p2m_domain *p2m)
diff --git a/xen/common/smp.c b/xen/common/smp.c
index 79f4ebd145..781bcf2c24 100644
--- a/xen/common/smp.c
+++ b/xen/common/smp.c
@@ -87,7 +87,11 @@ void smp_call_function_interrupt(void)
 
     irq_enter();
 
-    if ( call_data.wait )
+    if ( unlikely(!func) )
+    {
+        cpumask_clear_cpu(cpu, &call_data.selected);
+    }
+    else if ( call_data.wait )
     {
         (*func)(info);
         smp_mb();
--
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