[xen stable-4.16] IOMMU/x86: work around bogus gcc12 warning in hvm_gsi_eoi()

[patchbot@xxxxxxx]

commit 460b08d6c6c16b3f32aa138e772b759ae02a4479
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Jul 12 11:10:34 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Jul 12 11:10:34 2022 +0200

    IOMMU/x86: work around bogus gcc12 warning in hvm_gsi_eoi()
    
    As per [1] the expansion of the pirq_dpci() macro causes a -Waddress
    controlled warning (enabled implicitly in our builds, if not by default)
    tying the middle part of the involved conditional expression to the
    surrounding boolean context. Work around this by introducing a local
    inline function in the affected source file.
    
    Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    
    [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102967
    master commit: 80ad8db8a4d9bb24952f0aea788ce6f47566fa76
    master date: 2022-06-15 10:19:32 +0200
---
 xen/drivers/passthrough/x86/hvm.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/xen/drivers/passthrough/x86/hvm.c 
b/xen/drivers/passthrough/x86/hvm.c
index 0b37cd145b..ba0f6c53d7 100644
--- a/xen/drivers/passthrough/x86/hvm.c
+++ b/xen/drivers/passthrough/x86/hvm.c
@@ -25,6 +25,18 @@
 #include <asm/hvm/support.h>
 #include <asm/io_apic.h>
 
+/*
+ * Gcc12 takes issue with pirq_dpci() being used in boolean context (see gcc
+ * bug 102967). While we can't replace the macro definition in the header by an
+ * inline function, we can do so here.
+ */
+static inline struct hvm_pirq_dpci *_pirq_dpci(struct pirq *pirq)
+{
+    return pirq_dpci(pirq);
+}
+#undef pirq_dpci
+#define pirq_dpci(pirq) _pirq_dpci(pirq)
+
 static DEFINE_PER_CPU(struct list_head, dpci_list);
 
 /*
--
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