linux-kernel - [PATCH] x86/xen: Improve failed hypercall debugging

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Message-Id: <1eda2acc5ed68b41f24ba7ab2672976fd92a7f9e.1493747901.git.luto@kernel.org>
Date:   Tue,  2 May 2017 10:59:22 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     xen-devel@...ts.xenproject.org
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Juergen Gross <jgross@...e.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: [PATCH] x86/xen: Improve failed hypercall debugging

When fiddling with xen_exit_mmap(), I noticed that failed multicall
debugging doesn't work if the multicall is just one call.  Fix it.

Cc: Juergen Gross <jgross@...e.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/xen/multicalls.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/arch/x86/xen/multicalls.c b/arch/x86/xen/multicalls.c
index ea54a08d8301..b6b3f024d342 100644
--- a/arch/x86/xen/multicalls.c
+++ b/arch/x86/xen/multicalls.c
@@ -96,23 +96,23 @@ void xen_mc_flush(void)
 		for (i = 0; i < b->mcidx; i++)
 			if (b->entries[i].result < 0)
 				ret++;
+	}
 
 #if MC_DEBUG
-		if (ret) {
-			printk(KERN_ERR "%d multicall(s) failed: cpu %d\n",
-			       ret, smp_processor_id());
-			dump_stack();
-			for (i = 0; i < b->mcidx; i++) {
-				printk(KERN_DEBUG "  call %2d/%d: op=%lu arg=[%lx] result=%ld\t%pF\n",
-				       i+1, b->mcidx,
-				       b->debug[i].op,
-				       b->debug[i].args[0],
-				       b->entries[i].result,
-				       b->caller[i]);
-			}
+	if (ret) {
+		printk(KERN_ERR "%d multicall(s) failed: cpu %d\n",
+		       ret, smp_processor_id());
+		dump_stack();
+		for (i = 0; i < b->mcidx; i++) {
+			printk(KERN_DEBUG "  call %2d/%d: op=%lu arg=[%lx] result=%ld\t%pF\n",
+			       i+1, b->mcidx,
+			       b->debug[i].op,
+			       b->debug[i].args[0],
+			       b->entries[i].result,
+			       b->caller[i]);
 		}
-#endif
 	}
+#endif
 
 	b->mcidx = 0;
 	b->argidx = 0;
-- 
2.9.3