On 3/1/2024 6:17 PM, Gerd Hoffmann wrote:
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);
I think you misunderstand this field.
If you expose this field to guest, it's the information for nested
guest. i.e., the guest itself runs as a hypervisor will know its nested
guest can have guest_phys_bits for physical addr.
}
*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
