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


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