[PATCH 1/1] kvm: add support for guest physical bits

[Gerd Hoffmann <kraxel@xxxxxxxxxx>]

query kvm for supported guest physical address bits using
KVM_CAP_VM_GPA_BITS.  Expose the value to the guest via cpuid
(leaf 0x80000008, eax, bits 16-23).

Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
---
 target/i386/cpu.h     | 1 +
 target/i386/cpu.c     | 1 +
 target/i386/kvm/kvm.c | 8 ++++++++
 3 files changed, 10 insertions(+)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 952174bb6f52..d427218827f6 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -2026,6 +2026,7 @@ struct ArchCPU {
 
     /* Number of physical address bits supported */
     uint32_t phys_bits;
+    uint32_t guest_phys_bits;
 
     /* in order to simplify APIC support, we leave this pointer to the
        user */
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 2666ef380891..1a6cfc75951e 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6570,6 +6570,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         if (env->features[FEAT_8000_0001_EDX] & CPUID_EXT2_LM) {
             /* 64 bit processor */
              *eax |= (cpu_x86_virtual_addr_width(env) << 8);
+             *eax |= (cpu->guest_phys_bits << 16);
         }
         *ebx = env->features[FEAT_8000_0008_EBX];
         if (cs->nr_cores * cs->nr_threads > 1) {
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 42970ab046fa..e06c9d66bb01 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1716,6 +1716,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
     X86CPU *cpu = X86_CPU(cs);
     CPUX86State *env = &cpu->env;
     uint32_t limit, i, j, cpuid_i;
+    uint32_t guest_phys_bits;
     uint32_t unused;
     struct kvm_cpuid_entry2 *c;
     uint32_t signature[3];
@@ -1751,6 +1752,13 @@ int kvm_arch_init_vcpu(CPUState *cs)
 
     env->apic_bus_freq = KVM_APIC_BUS_FREQUENCY;
 
+    guest_phys_bits = kvm_check_extension(cs->kvm_state, KVM_CAP_VM_GPA_BITS);
+    if (guest_phys_bits &&
+        (cpu->guest_phys_bits == 0 ||
+         cpu->guest_phys_bits > guest_phys_bits)) {
+        cpu->guest_phys_bits = guest_phys_bits;
+    }
+
     /*
      * kvm_hyperv_expand_features() is called here for the second time in case
      * KVM_CAP_SYS_HYPERV_CPUID is not supported. While we can't possibly handle
-- 
2.44.0