From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
A special case based on the previous phys-bits property; if it's
the magic value 0 then use the hosts capabilities.
This becomes the default on new machine types.
Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
---
include/hw/i386/pc.h | 5 +++++
target-i386/cpu.c | 36 +++++++++++++++++++++++++++++++++++-
2 files changed, 40 insertions(+), 1 deletion(-)
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index d85e924..bf31609 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -379,6 +379,11 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
.driver = TYPE_X86_CPU,\
.property = "fill-mtrr-mask",\
.value = "off",\
+ },\
+ {\
+ .driver = TYPE_X86_CPU,\
+ .property = "phys-bits",\
+ .value = "40",\
},
#define PC_COMPAT_2_5 \
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 5737aba..d45d2a6 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -2957,6 +2957,40 @@ static void x86_cpu_realizefn(DeviceState *dev, Error
**errp)
& CPUID_EXT2_AMD_ALIASES);
}
+ /* For 64bit systems think about the number of physical bits to present.
+ * ideally this should be the same as the host; anything other than
matching
+ * the host can cause incorrect guest behaviour.
+ * QEMU used to pick the magic value of 40 bits that corresponds to
+ * consumer AMD devices but nothing esle.
+ */
+ if (env->features[FEAT_8000_0001_EDX] & CPUID_EXT2_LM) {
+ uint32_t eax;
+ /* Read the hosts physical address size, and compare it to what we
+ * were asked for; note old machine types default to 40 bits
+ */
+ uint32_t host_phys_bits = 0;
+ host_cpuid(0x80000000, 0, &eax, NULL, NULL, NULL);
+ if (eax >= 0x80000008) {
+ host_cpuid(0x80000008, 0, &eax, NULL, NULL, NULL);
+ /* Note: According to AMD doc 25481 rev 2.34 they have a field
+ * at 23:16 that can specify a maximum physical address bits for
+ * the guest that can override this value; but I've not seen
+ * anything with that set.
+ */
+ host_phys_bits = eax & 0xff;
+ } else {
+ /* It's an odd 64 bit machine that doesn't have the leaf for
+ * physical address bits; fall back to 36 that's most older Intel.
+ */
+ host_phys_bits = 36;
+ }
+
+ if (cpu->phys_bits == 0) {
+ /* The user asked for us to use the host physical bits */
+ cpu->phys_bits = host_phys_bits;
+
+ }
+ }
cpu_exec_init(cs, &error_abort);
@@ -3259,7 +3293,7 @@ static Property x86_cpu_properties[] = {
DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false),
DEFINE_PROP_BOOL("kvm", X86CPU, expose_kvm, true),
DEFINE_PROP_BOOL("fill-mtrr-mask", X86CPU, fill_mtrr_mask, true),
- DEFINE_PROP_UINT32("phys-bits", X86CPU, phys_bits, 40),
+ DEFINE_PROP_UINT32("phys-bits", X86CPU, phys_bits, 0),
DEFINE_PROP_UINT32("level", X86CPU, env.cpuid_level, 0),
DEFINE_PROP_UINT32("xlevel", X86CPU, env.cpuid_xlevel, 0),
DEFINE_PROP_UINT32("xlevel2", X86CPU, env.cpuid_xlevel2, 0),
--
2.7.4
