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| author | Nadav Har'El | 2011-05-25 22:02:23 +0200 |
|---|---|---|
| committer | Avi Kivity | 2011-07-12 10:45:09 +0200 |
| commit | 801d342432190947928e18f893f073fd87cd8bdf (patch) | |
| tree | 3967b58452246c2064741b0591fd076724c19bc7 /arch/x86/kvm/vmx.c | |
| parent | KVM: x86 emulator: Avoid clearing the whole decode_cache (diff) | |
| download | kernel-qcow2-linux-801d342432190947928e18f893f073fd87cd8bdf.tar.gz kernel-qcow2-linux-801d342432190947928e18f893f073fd87cd8bdf.tar.xz kernel-qcow2-linux-801d342432190947928e18f893f073fd87cd8bdf.zip | |
KVM: nVMX: Add "nested" module option to kvm_intel
This patch adds to kvm_intel a module option "nested". This option controls
whether the guest can use VMX instructions, i.e., whether we allow nested
virtualization. A similar, but separate, option already exists for the
SVM module.
This option currently defaults to 0, meaning that nested VMX must be
explicitly enabled by giving nested=1. When nested VMX matures, the default
should probably be changed to enable nested VMX by default - just like
nested SVM is currently enabled by default.
Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'arch/x86/kvm/vmx.c')
| -rw-r--r-- | arch/x86/kvm/vmx.c | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 1444e4149c4d..263be2debde8 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -74,6 +74,14 @@ module_param(vmm_exclusive, bool, S_IRUGO); static int __read_mostly yield_on_hlt = 1; module_param(yield_on_hlt, bool, S_IRUGO); +/* + * If nested=1, nested virtualization is supported, i.e., guests may use + * VMX and be a hypervisor for its own guests. If nested=0, guests may not + * use VMX instructions. + */ +static int __read_mostly nested = 0; +module_param(nested, bool, S_IRUGO); + #define KVM_GUEST_CR0_MASK_UNRESTRICTED_GUEST \ (X86_CR0_WP | X86_CR0_NE | X86_CR0_NW | X86_CR0_CD) #define KVM_GUEST_CR0_MASK \ @@ -1292,6 +1300,23 @@ static u64 vmx_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc) return target_tsc - native_read_tsc(); } +static bool guest_cpuid_has_vmx(struct kvm_vcpu *vcpu) +{ + struct kvm_cpuid_entry2 *best = kvm_find_cpuid_entry(vcpu, 1, 0); + return best && (best->ecx & (1 << (X86_FEATURE_VMX & 31))); +} + +/* + * nested_vmx_allowed() checks whether a guest should be allowed to use VMX + * instructions and MSRs (i.e., nested VMX). Nested VMX is disabled for + * all guests if the "nested" module option is off, and can also be disabled + * for a single guest by disabling its VMX cpuid bit. + */ +static inline bool nested_vmx_allowed(struct kvm_vcpu *vcpu) +{ + return nested && guest_cpuid_has_vmx(vcpu); +} + /* * Reads an msr value (of 'msr_index') into 'pdata'. * Returns 0 on success, non-0 otherwise. |