[Xen-devel] [PATCH] x86/MSI: fix guest unmasking when handling IRQ via event channel

["Jan Beulich" <JBeulich@xxxxxxxx>]

Rather than assuming only PV guests need special treatment (and
dealing with that directly when an IRQ gets set up), keep all guest MSI
IRQs masked until either the (HVM) guest unmasks them via vMSI or the
(PV, PVHVM, or PVH) guest sets up an event channel for it.

To not further clutter the common evtchn_bind_pirq() with x86-specific
code, introduce an arch_evtchn_bind_pirq() hook instead.

Reported-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Tested-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>

--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -2502,6 +2502,25 @@ int unmap_domain_pirq_emuirq(struct doma
     return ret;
 }
 
+void arch_evtchn_bind_pirq(struct domain *d, int pirq)
+{
+    int irq = domain_pirq_to_irq(d, pirq);
+    struct irq_desc *desc;
+    unsigned long flags;
+
+    if ( irq <= 0 )
+        return;
+
+    if ( is_hvm_domain(d) )
+        map_domain_emuirq_pirq(d, pirq, IRQ_PT);
+
+    desc = irq_to_desc(irq);
+    spin_lock_irqsave(&desc->lock, flags);
+    if ( desc->msi_desc )
+        guest_mask_msi_irq(desc, 0);
+    spin_unlock_irqrestore(&desc->lock, flags);
+}
+
 bool_t hvm_domain_use_pirq(const struct domain *d, const struct pirq *pirq)
 {
     return is_hvm_domain(d) && pirq &&
--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -422,10 +422,7 @@ void guest_mask_msi_irq(struct irq_desc 
 
 static unsigned int startup_msi_irq(struct irq_desc *desc)
 {
-    bool_t guest_masked = (desc->status & IRQ_GUEST) &&
-                          is_hvm_domain(desc->msi_desc->dev->domain);
-
-    msi_set_mask_bit(desc, 0, guest_masked);
+    msi_set_mask_bit(desc, 0, !!(desc->status & IRQ_GUEST));
     return 0;
 }
 
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -502,10 +502,7 @@ static long evtchn_bind_pirq(evtchn_bind
 
     bind->port = port;
 
-#ifdef CONFIG_X86
-    if ( is_hvm_domain(d) && domain_pirq_to_irq(d, pirq) > 0 )
-        map_domain_emuirq_pirq(d, pirq, IRQ_PT);
-#endif
+    arch_evtchn_bind_pirq(d, pirq);
 
  out:
     spin_unlock(&d->event_lock);
--- a/xen/include/asm-arm/irq.h
+++ b/xen/include/asm-arm/irq.h
@@ -47,6 +47,8 @@ int release_guest_irq(struct domain *d, 
 
 void arch_move_irqs(struct vcpu *v);
 
+#define arch_evtchn_bind_pirq(d, pirq) ((void)((d) + (pirq)))
+
 /* Set IRQ type for an SPI */
 int irq_set_spi_type(unsigned int spi, unsigned int type);
 
--- a/xen/include/xen/irq.h
+++ b/xen/include/xen/irq.h
@@ -172,4 +172,8 @@ unsigned int set_desc_affinity(struct ir
 unsigned int arch_hwdom_irqs(domid_t);
 #endif
 
+#ifndef arch_evtchn_bind_pirq
+void arch_evtchn_bind_pirq(struct domain *, int pirq);
+#endif
+
 #endif /* __XEN_IRQ_H__ */

Attachment: x86-MSI-pv-unmask.patch
Description: Text document

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