[PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Yan Li <elliot.li.tech@gmail.com>]

Since the mtrr empty was detected very early before we can use DMI or
PCI to check whether we are running as a VMware guest or not, we now
only print an info there. Warning will only be issued later when we
are sure that we are not running as a VMware guest.

mtrr_trim_uncached_memory() is modified to return meaningful codes for
later warning decision.

Signed-off-by: Yan Li <elliot.li.tech@gmail.com>
---
 arch/x86/kernel/cpu/mtrr/main.c |   16 +++++++++++++++-
 arch/x86/kernel/setup.c         |   27 ++++++++++++++++++++++++++-
 include/asm-x86/mtrr.h          |    2 ++
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index b117d7f..95d1cc0 100644
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -1453,6 +1453,11 @@ static u64 __init real_trim_memory(unsigned long start_pfn,
  * all of the memory the kernel is intending to use. If not, it'll trim any
  * memory off the end by adjusting end_pfn, removing it from the kernel's
  * allocation pools, warning the user with an obnoxious message.
+ *
+ * Return code:
+ * EMTRR_ALL_BLANK (-1):  not trimmed due to CPU MTRRs all blank
+ *                    0:  not trimmed due to other reasons
+ *                    1:  trimmed successfully
  */
 int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
 {
@@ -1494,11 +1499,20 @@ int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
 			highest_pfn = base + size;
 	}
 
-	/* kvm/qemu doesn't have mtrr set right, don't trim them all */
+	/* kvm/qemu/VMware doesn't have mtrr set right, don't trim them all */
 	if (!highest_pfn) {
+#ifdef CONFIG_VMWARE_GUEST_DETECT
+		/* the "mtrr all blank" warning will be deferred until
+		 * after DMI scanning and we know the machine is not a
+		 * VMware guest
+		 */
+		printk(KERN_INFO "CPU MTRRs all blank\n");
+		return EMTRR_ALL_BLANK;
+#else
 		WARN(!kvm_para_available(), KERN_WARNING
 				"WARNING: strange, CPU MTRRs all blank?\n");
 		return 0;
+#endif
 	}
 
 	/* check entries number */
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 9838f25..4cbec10 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -102,6 +102,7 @@
 #include <asm/percpu.h>
 #include <asm/topology.h>
 #include <asm/apicdef.h>
+#include <asm/vmware.h>
 #ifdef CONFIG_X86_64
 #include <asm/numa_64.h>
 #endif
@@ -593,6 +594,13 @@ struct x86_quirks *x86_quirks __initdata = &default_x86_quirks;
 
 void __init setup_arch(char **cmdline_p)
 {
+#ifdef CONFIG_VMWARE_GUEST_DETECT
+	/* the "mtrr all blank" warning will be deferred until after
+	 * DMI scanning and we know the machine is not a VMware guest
+	 */
+	int cpu_mtrr_all_blank_later_warning = 0;
+#endif
+
 #ifdef CONFIG_X86_32
 	memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
 	visws_early_detect();
@@ -733,8 +741,16 @@ void __init setup_arch(char **cmdline_p)
 	early_reserve_e820_mpc_new();
 	/* update e820 for memory not covered by WB MTRRs */
 	mtrr_bp_init();
-	if (mtrr_trim_uncached_memory(max_pfn))
+	switch (mtrr_trim_uncached_memory(max_pfn)) {
+	case 1:
 		max_pfn = e820_end_of_ram_pfn();
+		break;
+#ifdef CONFIG_VMWARE_GUEST_DETECT
+	case EMTRR_ALL_BLANK:
+		cpu_mtrr_all_blank_later_warning = 1;
+		break;
+#endif
+	}
 
 #ifdef CONFIG_X86_32
 	/* max_low_pfn get updated here */
@@ -783,6 +799,15 @@ void __init setup_arch(char **cmdline_p)
 
 	dmi_scan_machine();
 
+#ifdef CONFIG_VMWARE_GUEST_DETECT
+	if (cpu_mtrr_all_blank_later_warning) {
+		WARN(!(kvm_para_available() || (is_vmware_guest())),
+		     KERN_WARNING
+		     "WARNING: strange, CPU MTRRs all blank? "
+		     "Deferred from mtrr_trim_uncached_memory()\n");
+	}
+#endif
+
 	io_delay_init();
 
 	/*
diff --git a/include/asm-x86/mtrr.h b/include/asm-x86/mtrr.h
index a69a01a..b6d8fcb 100644
--- a/include/asm-x86/mtrr.h
+++ b/include/asm-x86/mtrr.h
@@ -26,6 +26,8 @@
 #include <linux/ioctl.h>
 #include <linux/errno.h>
 
+#define	EMTRR_ALL_BLANK (-1)
+
 #define	MTRR_IOCTL_BASE	'M'
 
 struct mtrr_sentry {
-- 
1.5.4.3


-- 
Li, Yan

"Everything that is really great and inspiring is created by the
individual who can labor in freedom."
              - Albert Einstein, in Out of My Later Years (1950)