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Subject[PATCH] x86/hyperv: suppress "PCI: Fatal: No config space access function found"
Date

A Generatin-2 Linux VM on Hyper-V doesn't have the legacy PCI bus, and
users always see the scary warning, which is actually harmless. The patch
is made to suppress the warning.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
---
arch/x86/hyperv/hv_init.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 20c876c..7abb09e 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -17,6 +17,7 @@
*
*/

+#include <linux/efi.h>
#include <linux/types.h>
#include <asm/apic.h>
#include <asm/desc.h>
@@ -253,6 +254,22 @@ static int hv_cpu_die(unsigned int cpu)
return 0;
}

+static int __init hv_pci_init(void)
+{
+ int gen2vm = efi_enabled(EFI_BOOT);
+
+ /*
+ * For Generation-2 VM, we exit from pci_arch_init() by returning 0.
+ * The purpose is to suppress the harmless warning:
+ * "PCI: Fatal: No config space access function found"
+ */
+ if (gen2vm)
+ return 0;
+
+ /* For Generation-1 VM, we'll proceed in pci_arch_init(). */
+ return 1;
+}
+
/*
* This function is to be invoked early in the boot sequence after the
* hypervisor has been detected.
@@ -329,6 +346,8 @@ void __init hyperv_init(void)

hv_apic_init();

+ x86_init.pci.arch_init = hv_pci_init;
+
/*
* Register Hyper-V specific clocksource.
*/
--
2.7.4
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