KVM, pkeys: save/restore PKRU when guest/host switches
Currently XSAVE state of host is not restored after VM-exit and PKRU
is managed by XSAVE so the PKRU from guest is still controlling the
memory access even if the CPU is running the code of host. This is
not safe as KVM needs to access the memory of userspace (e,g QEMU) to
do some emulation.
So we save/restore PKRU when guest/host switches.
Signed-off-by: Huaitong Han <huaitong.han@intel.com>
Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1b8a41f..8766477 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -598,6 +598,10 @@
struct page *pml_pg;
u64 current_tsc_ratio;
+
+ bool guest_pkru_valid;
+ u32 guest_pkru;
+ u32 host_pkru;
};
enum segment_cache_field {
@@ -2107,6 +2111,7 @@
} while (cmpxchg(&pi_desc->control, old.control,
new.control) != old.control);
}
+
/*
* Switches to specified vcpu, until a matching vcpu_put(), but assumes
* vcpu mutex is already taken.
@@ -2167,6 +2172,7 @@
}
vmx_vcpu_pi_load(vcpu, cpu);
+ vmx->host_pkru = read_pkru();
}
static void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu)
@@ -8639,6 +8645,9 @@
if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
vmx_set_interrupt_shadow(vcpu, 0);
+ if (vmx->guest_pkru_valid)
+ __write_pkru(vmx->guest_pkru);
+
atomic_switch_perf_msrs(vmx);
debugctlmsr = get_debugctlmsr();
@@ -8779,6 +8788,20 @@
vmx->exit_reason = vmcs_read32(VM_EXIT_REASON);
/*
+ * eager fpu is enabled if PKEY is supported and CR4 is switched
+ * back on host, so it is safe to read guest PKRU from current
+ * XSAVE.
+ */
+ if (boot_cpu_has(X86_FEATURE_OSPKE)) {
+ vmx->guest_pkru = __read_pkru();
+ if (vmx->guest_pkru != vmx->host_pkru) {
+ vmx->guest_pkru_valid = true;
+ __write_pkru(vmx->host_pkru);
+ } else
+ vmx->guest_pkru_valid = false;
+ }
+
+ /*
* the KVM_REQ_EVENT optimization bit is only on for one entry, and if
* we did not inject a still-pending event to L1 now because of
* nested_run_pending, we need to re-enable this bit.
