[xen staging] x86/dpci: do not remove pirqs from domain tree on unbind

[patchbot@xxxxxxx]

commit 58427889f5a420cc5226f88524b3228f90b72a58
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Thu Jan 21 16:11:41 2021 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Jan 21 16:11:41 2021 +0100

    x86/dpci: do not remove pirqs from domain tree on unbind
    
    A fix for a previous issue removed the pirqs from the domain tree when
    they are unbound in order to prevent shared pirqs from triggering a
    BUG_ON in __pirq_guest_unbind if they are unbound multiple times. That
    caused free_domain_pirqs to no longer unmap the pirqs because they
    are gone from the domain pirq tree, thus leaving stale unbound pirqs
    after domain destruction if the domain had mapped dpci pirqs after
    shutdown.
    
    Take a different approach to fix the original issue, instead of
    removing the pirq from d->pirq_tree clear the flags of the dpci pirq
    struct to signal that the pirq is now unbound. This prevents calling
    pirq_guest_unbind multiple times for the same pirq without having to
    remove it from the domain pirq tree.
    
    This is XSA-360.
    
    Fixes: 5b58dad089 ('x86/pass-through: avoid double IRQ unbind during domain 
cleanup')
    Reported-by: Samuel Verschelde <samuel.verschelde@xxxxxxxx>
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/irq.c                |  2 +-
 xen/drivers/passthrough/x86/hvm.c | 27 ++++++++-------------------
 xen/include/asm-x86/hvm/irq.h     |  2 --
 3 files changed, 9 insertions(+), 22 deletions(-)

diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 21881a1345..032fe82167 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -1349,7 +1349,7 @@ void (pirq_cleanup_check)(struct pirq *pirq, struct 
domain *d)
     }
 
     if ( radix_tree_delete(&d->pirq_tree, pirq->pirq) != pirq )
-        BUG_ON(!d->is_dying);
+        BUG();
 }
 
 /* Flush all ready EOIs from the top of this CPU's pending-EOI stack. */
diff --git a/xen/drivers/passthrough/x86/hvm.c 
b/xen/drivers/passthrough/x86/hvm.c
index edc8059518..a6e2863c14 100644
--- a/xen/drivers/passthrough/x86/hvm.c
+++ b/xen/drivers/passthrough/x86/hvm.c
@@ -1036,6 +1036,10 @@ static int pci_clean_dpci_irq(struct domain *d,
 {
     struct dev_intx_gsi_link *digl, *tmp;
 
+    if ( !pirq_dpci->flags )
+        /* Already processed. */
+        return 0;
+
     pirq_guest_unbind(d, dpci_pirq(pirq_dpci));
 
     if ( pt_irq_need_timer(pirq_dpci->flags) )
@@ -1046,15 +1050,10 @@ static int pci_clean_dpci_irq(struct domain *d,
         list_del(&digl->list);
         xfree(digl);
     }
+    /* Note the pirq is now unbound. */
+    pirq_dpci->flags = 0;
 
-    radix_tree_delete(&d->pirq_tree, dpci_pirq(pirq_dpci)->pirq);
-
-    if ( !pt_pirq_softirq_active(pirq_dpci) )
-        return 0;
-
-    domain_get_irq_dpci(d)->pending_pirq_dpci = pirq_dpci;
-
-    return -ERESTART;
+    return pt_pirq_softirq_active(pirq_dpci) ? -ERESTART : 0;
 }
 
 int arch_pci_clean_pirqs(struct domain *d)
@@ -1071,18 +1070,8 @@ int arch_pci_clean_pirqs(struct domain *d)
     hvm_irq_dpci = domain_get_irq_dpci(d);
     if ( hvm_irq_dpci != NULL )
     {
-        int ret = 0;
-
-        if ( hvm_irq_dpci->pending_pirq_dpci )
-        {
-            if ( pt_pirq_softirq_active(hvm_irq_dpci->pending_pirq_dpci) )
-                 ret = -ERESTART;
-            else
-                 hvm_irq_dpci->pending_pirq_dpci = NULL;
-        }
+        int ret = pt_pirq_iterate(d, pci_clean_dpci_irq, NULL);
 
-        if ( !ret )
-            ret = pt_pirq_iterate(d, pci_clean_dpci_irq, NULL);
         if ( ret )
         {
             spin_unlock(&d->event_lock);
diff --git a/xen/include/asm-x86/hvm/irq.h b/xen/include/asm-x86/hvm/irq.h
index 532880d497..7f76f6c437 100644
--- a/xen/include/asm-x86/hvm/irq.h
+++ b/xen/include/asm-x86/hvm/irq.h
@@ -160,8 +160,6 @@ struct hvm_irq_dpci {
     DECLARE_BITMAP(isairq_map, NR_ISAIRQS);
     /* Record of mapped Links */
     uint8_t link_cnt[NR_LINK];
-    /* Clean up: Entry with a softirq invocation pending / in progress. */
-    struct hvm_pirq_dpci *pending_pirq_dpci;
 };
 
 /* Machine IRQ to guest device/intx mapping. */
--
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