[Xen-ia64-devel] [PATCH] Fix SMP-unsafe with XENMEM_add_to_physmap on HVM

[Kouya Shimura <kouya@xxxxxxxxxxxxxx>]

XENMEM_add_to_physmap hypercall on HVM is SMP-unsafe
and may cause a xen crash.

Actually I've met:

(XEN) ia64_fault, vector=0x18, ifa=0xe0000165c98814f0, iip=0xf0000000040a1b80, 
ipsr=0x0000121008226010, isr=0x0000008000000030
(XEN) General Exception: IA-64 Reserved Register/Field fault (data access).
...
(XEN) ****************************************
(XEN) Panic on CPU 2:
(XEN) Fault in Xen.
(XEN) ****************************************

This patch fixes it.

Signed-off-by: Kouya Shimura <kouya@xxxxxxxxxxxxxx>

diff -r 08f77df14cba xen/arch/ia64/xen/vhpt.c
--- a/xen/arch/ia64/xen/vhpt.c  Wed Jul 02 11:30:37 2008 +0900
+++ b/xen/arch/ia64/xen/vhpt.c  Fri Jul 04 09:35:32 2008 +0900
@@ -243,37 +243,34 @@
        }
 }
 
+static void __vmx_vcpu_flush_vtlb_all(void *arg)
+{
+       struct vcpu *v = arg;
+
+       BUG_ON(vcpu_runnable(v) || v->is_running);
+       thash_purge_all(v);
+}
+
 // SMP: we can't assume v == current, vcpu might move to another physical cpu.
 // So memory barrier is necessary.
 // if we can guranttee that vcpu can run on only this physical cpu
 // (e.g. vcpu == current), smp_mb() is unnecessary.
 void vcpu_flush_vtlb_all(struct vcpu *v)
 {
-       if (VMX_DOMAIN(v)) {
-               /* This code may be call for remapping shared_info and
-                  grant_table share page from guest_physmap_remove_page()
-                  in arch_memory_op() XENMEM_add_to_physmap to realize
-                  PV-on-HVM feature. */
-               /* FIXME: This is not SMP-safe yet about p2m table */
-               /* Purge vTLB for VT-i domain */
-               thash_purge_all(v);
-       }
-       else {
-               /* First VCPU tlb.  */
-               vcpu_purge_tr_entry(&PSCBX(v,dtlb));
-               vcpu_purge_tr_entry(&PSCBX(v,itlb));
-               smp_mb();
+       /* First VCPU tlb.  */
+       vcpu_purge_tr_entry(&PSCBX(v,dtlb));
+       vcpu_purge_tr_entry(&PSCBX(v,itlb));
+       smp_mb();
 
-               /* Then VHPT.  */
-               if (HAS_PERVCPU_VHPT(v->domain))
-                       vcpu_vhpt_flush(v);
-               else
-                       local_vhpt_flush();
-               smp_mb();
+       /* Then VHPT.  */
+       if (HAS_PERVCPU_VHPT(v->domain))
+               vcpu_vhpt_flush(v);
+       else
+               local_vhpt_flush();
+       smp_mb();
 
-               /* Then mTLB.  */
-               local_flush_tlb_all();
-       }
+       /* Then mTLB.  */
+       local_flush_tlb_all();
 
        /* We could clear bit in d->domain_dirty_cpumask only if domain d in
           not running on this processor.  There is currently no easy way to
@@ -296,6 +293,30 @@
        for_each_vcpu(d, v) {
                if (!v->is_initialised)
                        continue;
+
+               if (VMX_DOMAIN(v)) {
+                       /*
+                        * This code may be call for remapping shared_info
+                        * and grant_table from guest_physmap_remove_page()
+                        * in arch_memory_op() XENMEM_add_to_physmap to realize
+                        * PV-on-HVM feature.
+                        */
+
+                       if (v == current) {
+                               /* Purge vTLB for VT-i domain */
+                               thash_purge_all(v);
+                               continue;
+                       }
+
+                       vcpu_pause(v);
+                       if (v->processor == cpu)
+                               thash_purge_all(v);
+                       else
+                               smp_call_function_single(v->processor,
+                                       __vmx_vcpu_flush_vtlb_all, v, 1, 1);
+                       vcpu_unpause(v);
+                       continue;
+               }
 
                if (v->processor == cpu)
                        vcpu_flush_vtlb_all(v);

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