[PATCH v3 21/25] KVM: VMX: Move LOAD_IA32_PERF_GLOBAL_CTRL errata handling out of setup_vmcs_config()

Vitaly Kuznetsov
2022-07-08T14:44:06Z

As a preparation to reusing the result of setup_vmcs_config() for setting
up nested VMX control MSRs, move LOAD_IA32_PERF_GLOBAL_CTRL errata handling
to vmx_vmexit_ctrl()/vmx_vmentry_ctrl() and print the warning from
hardware_setup(). While it seems reasonable to not expose
LOAD_IA32_PERF_GLOBAL_CTRL controls to L1 hypervisor on buggy CPUs,
such change would inevitably break live migration from older KVMs
where the controls are exposed. Keep the status quo for know, L1 hypervisor
itself is supposed to take care of the errata.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/vmx/vmx.c | 62 ++++++++++++++++++++++++++----------------
1 file changed, 38 insertions(+), 24 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 2dff5b94c535..e462e5b9c0a1 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2416,6 +2416,31 @@ static bool cpu_has_sgx(void)
return cpuid_eax(0) >= 0x12 && (cpuid_eax(0x12) & BIT(0));
}

+/*
+ * Some cpus support VM_{ENTRY,EXIT}_IA32_PERF_GLOBAL_CTRL but they
+ * can't be used due to errata where VM Exit may incorrectly clear
+ * IA32_PERF_GLOBAL_CTRL[34:32]. Work around the errata by using the
+ * MSR load mechanism to switch IA32_PERF_GLOBAL_CTRL.
+ */
+static bool cpu_has_perf_global_ctrl_bug(void)
+{
+ if (boot_cpu_data.x86 == 0x6) {
+ switch (boot_cpu_data.x86_model) {
+ case INTEL_FAM6_NEHALEM_EP: /* AAK155 */
+ case INTEL_FAM6_NEHALEM: /* AAP115 */
+ case INTEL_FAM6_WESTMERE: /* AAT100 */
+ case INTEL_FAM6_WESTMERE_EP: /* BC86,AAY89,BD102 */
+ case INTEL_FAM6_NEHALEM_EX: /* BA97 */
+ return true;
+ default:
+ break;
+ }
+ }
+
+ return false;
+}
+
+
static __init int adjust_vmx_controls(u32 ctl_min, u32 ctl_opt,
u32 msr, u32 *result)
{
@@ -2572,30 +2597,6 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
_vmexit_control &= ~x_ctrl;
}

- /*
- * Some cpus support VM_{ENTRY,EXIT}_IA32_PERF_GLOBAL_CTRL but they
- * can't be used due to an errata where VM Exit may incorrectly clear
- * IA32_PERF_GLOBAL_CTRL[34:32]. Workaround the errata by using the
- * MSR load mechanism to switch IA32_PERF_GLOBAL_CTRL.
- */
- if (boot_cpu_data.x86 == 0x6) {
- switch (boot_cpu_data.x86_model) {
- case INTEL_FAM6_NEHALEM_EP: /* AAK155 */
- case INTEL_FAM6_NEHALEM: /* AAP115 */
- case INTEL_FAM6_WESTMERE: /* AAT100 */
- case INTEL_FAM6_WESTMERE_EP: /* BC86,AAY89,BD102 */
- case INTEL_FAM6_NEHALEM_EX: /* BA97 */
- _vmentry_control &= ~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
- _vmexit_control &= ~VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
- pr_warn_once("kvm: VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL "
- "does not work properly. Using workaround\n");
- break;
- default:
- break;
- }
- }
-
-
rdmsr(MSR_IA32_VMX_BASIC, vmx_msr_low, vmx_msr_high);

/* IA-32 SDM Vol 3B: VMCS size is never greater than 4kB. */
@@ -4184,6 +4185,10 @@ static u32 vmx_vmentry_ctrl(void)
VM_ENTRY_LOAD_IA32_EFER |
VM_ENTRY_IA32E_MODE);

+
+ if (cpu_has_perf_global_ctrl_bug())
+ vmentry_ctrl &= ~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
+
return vmentry_ctrl;
}

@@ -4198,6 +4203,10 @@ static u32 vmx_vmexit_ctrl(void)
if (vmx_pt_mode_is_system())
vmexit_ctrl &= ~(VM_EXIT_PT_CONCEAL_PIP |
VM_EXIT_CLEAR_IA32_RTIT_CTL);
+
+ if (cpu_has_perf_global_ctrl_bug())
+ vmexit_ctrl &= ~VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
+
/* Loading of EFER and PERF_GLOBAL_CTRL are toggled dynamically */
return vmexit_ctrl &
~(VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL | VM_EXIT_LOAD_IA32_EFER);
@@ -8113,6 +8122,11 @@ static __init int hardware_setup(void)
if (setup_vmcs_config(&vmcs_config, &vmx_capability) < 0)
return -EIO;

+ if (cpu_has_perf_global_ctrl_bug()) {
+ pr_warn_once("kvm: VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL "
+ "does not work properly. Using workaround\n");
+ }
+
if (boot_cpu_has(X86_FEATURE_NX))
kvm_enable_efer_bits(EFER_NX);

--
2.35.3