Advertise UMIP as emulated if and only if the host doesn't natively
support UMIP, otherwise vmx_umip_emulated() is misleading when the host
_does_ support UMIP. Of the four users of vmx_umip_emulated(), two
already check for native support, and the logic in vmx_set_cpu_caps() is
relevant if and only if UMIP isn't natively supported as UMIP is set in
KVM's caps by kvm_set_cpu_caps() when UMIP is present in hardware.
That leaves KVM's stuffing of X86_CR4_UMIP into the default cr4_fixed1
value enumerated for nested VMX. In that case, checking for (lack of)
host support is actually a bug fix of sorts, as enumerating UMIP support
based solely on descriptor table exiting works only because KVM doesn't
sanity check MSR_IA32_VMX_CR4_FIXED1. E.g. if a (very theoretical) host
supported UMIP in hardware but didn't allow UMIP+VMX, KVM would advertise
UMIP but not actually emulate UMIP. Of course, KVM would explode long
before it could run a nested VM on said theoretical CPU, as KVM doesn't
modify host CR4 when enabling VMX, i.e. would load an "illegal" value into
vmcs.HOST_CR4.
Reported-by: Robert Hoo <robert.hu@intel.com>
Link: https://lore.kernel.org/all/20230310125718.1442088-2-robert.hu@intel.com
Link: https://lore.kernel.org/r/20230413231914.1482782-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
static inline bool vmx_umip_emulated(void)
{
- return vmcs_config.cpu_based_2nd_exec_ctrl &
- SECONDARY_EXEC_DESC;
+ return !boot_cpu_has(X86_FEATURE_UMIP) &&
+ (vmcs_config.cpu_based_2nd_exec_ctrl & SECONDARY_EXEC_DESC);
}
static inline bool cpu_has_vmx_rdtscp(void)
* Preset *DT exiting when emulating UMIP, so that vmx_set_cr4()
* will not have to rewrite the controls just for this bit.
*/
- if (!boot_cpu_has(X86_FEATURE_UMIP) && vmx_umip_emulated() &&
- (vmcs12->guest_cr4 & X86_CR4_UMIP))
+ if (vmx_umip_emulated() && (vmcs12->guest_cr4 & X86_CR4_UMIP))
exec_control |= SECONDARY_EXEC_DESC;
if (exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY)
else
hw_cr4 |= KVM_PMODE_VM_CR4_ALWAYS_ON;
- if (!boot_cpu_has(X86_FEATURE_UMIP) && vmx_umip_emulated()) {
+ if (vmx_umip_emulated()) {
if (cr4 & X86_CR4_UMIP) {
secondary_exec_controls_setbit(vmx, SECONDARY_EXEC_DESC);
hw_cr4 &= ~X86_CR4_UMIP;