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[Qemu-devel] [PATCH 3/3] mask out forbidden cpuid features
From: |
Glauber Costa |
Subject: |
[Qemu-devel] [PATCH 3/3] mask out forbidden cpuid features |
Date: |
Wed, 28 Jan 2009 14:02:05 -0500 |
KVM has a (so far unused) ioctl to inform userspace
about supported cpuid bits in the current host.
The lack of this kind of checking can lead to bugs in which
a cpuid bit is exposed but not supported by the host kernel
(an example is fedora bug https://bugzilla.redhat.com/show_bug.cgi?id=481274)
Signed-off-by: Glauber Costa <address@hidden>
---
target-i386/kvm.c | 44 +++++++++++++++++++++++++++++++++++++++-----
1 files changed, 39 insertions(+), 5 deletions(-)
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 87ddff5..08584dd 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -68,8 +68,18 @@ int kvm_arch_init_vcpu(CPUState *env)
struct kvm_cpuid2 cpuid;
struct kvm_cpuid_entry2 entries[100];
} __attribute__((packed)) cpuid_data;
- uint32_t limit, i, cpuid_i = 0;
+
+ struct {
+ struct kvm_cpuid2 cpuid;
+ struct kvm_cpuid_entry2 entries[100];
+ } __attribute__((packed)) cpuid_base_data;
+
+ uint32_t limit, i, r, cpuid_i = 0;
uint32_t eax, ebx, ecx, edx;
+ struct kvm_cpuid_entry2 *func1 = NULL;
+ struct kvm_cpuid_entry2 *ext_func1 = NULL;
+ uint32_t ecx_mask = ~0U;
+ uint32_t edx_mask = ~0U;
#ifdef KVM_CPUID_SIGNATURE
struct kvm_cpuid_entry2 *pv_ent;
@@ -89,32 +99,56 @@ int kvm_arch_init_vcpu(CPUState *env)
#endif
+ cpuid_base_data.cpuid.nent = 100;
+ r = kvm_ioctl(env->kvm_state, KVM_GET_SUPPORTED_CPUID, &cpuid_base_data);
+ if (r == -1)
+ cpuid_base_data.cpuid.nent = 0;
+
+ for (i = 0; i < cpuid_base_data.cpuid.nent; i++) {
+ if (cpuid_base_data.entries[i].function == 1)
+ func1 = &cpuid_base_data.entries[i];
+ if (cpuid_base_data.entries[i].function == 0x80000001)
+ ext_func1 = &cpuid_base_data.entries[i];
+ }
+
cpu_x86_cpuid(env, 0, &eax, &ebx, &ecx, &edx);
limit = eax;
for (i = 0; i <= limit; i++) {
struct kvm_cpuid_entry2 *c = &cpuid_data.entries[cpuid_i++];
+ if (func1 && (i == 1)) {
+ ecx_mask = func1->ecx;
+ edx_mask = func1->edx;
+ } else
+ ecx_mask = edx_mask = ~0U;
+
cpu_x86_cpuid(env, i, &eax, &ebx, &ecx, &edx);
c->function = i;
c->eax = eax;
c->ebx = ebx;
- c->ecx = ecx;
- c->edx = edx;
+ c->ecx = ecx & ecx_mask;
+ c->edx = edx & edx_mask;
}
cpu_x86_cpuid(env, 0x80000000, &eax, &ebx, &ecx, &edx);
limit = eax;
for (i = 0x80000000; i <= limit; i++) {
+
struct kvm_cpuid_entry2 *c = &cpuid_data.entries[cpuid_i++];
+ if (ext_func1 && (i == 0x80000001)) {
+ ecx_mask = ext_func1->ecx;
+ edx_mask = ext_func1->edx;
+ } else
+ ecx_mask = edx_mask = ~0U;
cpu_x86_cpuid(env, i, &eax, &ebx, &ecx, &edx);
c->function = i;
c->eax = eax;
c->ebx = ebx;
- c->ecx = ecx;
- c->edx = edx;
+ c->ecx = ecx & ecx_mask;
+ c->edx = edx & edx_mask;
}
cpuid_data.cpuid.nent = cpuid_i;
--
1.5.6.5