On 8/2/2025 10:33 AM, Xin Li wrote:
@@ -4531,6 +4593,27 @@ static void sync_vmcs02_to_vmcs12_rare(struct
kvm_vcpu *vcpu,
vmcs12->guest_tr_base = vmcs_readl(GUEST_TR_BASE);
vmcs12->guest_gdtr_base = vmcs_readl(GUEST_GDTR_BASE);
vmcs12->guest_idtr_base = vmcs_readl(GUEST_IDTR_BASE);
+
+ vmx->nested.pre_vmexit_fred_config =
vmcs_read64(GUEST_IA32_FRED_CONFIG);
+ vmx->nested.pre_vmexit_fred_rsp1 =
vmcs_read64(GUEST_IA32_FRED_RSP1);
+ vmx->nested.pre_vmexit_fred_rsp2 =
vmcs_read64(GUEST_IA32_FRED_RSP2);
+ vmx->nested.pre_vmexit_fred_rsp3 =
vmcs_read64(GUEST_IA32_FRED_RSP3);
+ vmx->nested.pre_vmexit_fred_stklvls =
vmcs_read64(GUEST_IA32_FRED_STKLVLS);
+ vmx->nested.pre_vmexit_fred_ssp1 =
vmcs_read64(GUEST_IA32_FRED_SSP1);
+ vmx->nested.pre_vmexit_fred_ssp2 =
vmcs_read64(GUEST_IA32_FRED_SSP2);
+ vmx->nested.pre_vmexit_fred_ssp3 =
vmcs_read64(GUEST_IA32_FRED_SSP3);
This ...
+
+ if (nested_cpu_save_guest_fred_state(vmcs12)) {
+ vmcs12->guest_ia32_fred_config = vmx-
>nested.pre_vmexit_fred_config;
+ vmcs12->guest_ia32_fred_rsp1 = vmx->nested.pre_vmexit_fred_rsp1;
+ vmcs12->guest_ia32_fred_rsp2 = vmx->nested.pre_vmexit_fred_rsp2;
+ vmcs12->guest_ia32_fred_rsp3 = vmx->nested.pre_vmexit_fred_rsp3;
+ vmcs12->guest_ia32_fred_stklvls = vmx-
>nested.pre_vmexit_fred_stklvls;
+ vmcs12->guest_ia32_fred_ssp1 = vmx->nested.pre_vmexit_fred_ssp1;
+ vmcs12->guest_ia32_fred_ssp2 = vmx->nested.pre_vmexit_fred_ssp2;
+ vmcs12->guest_ia32_fred_ssp3 = vmx->nested.pre_vmexit_fred_ssp3;
+ }
+
vmcs12->guest_pending_dbg_exceptions =
vmcs_readl(GUEST_PENDING_DBG_EXCEPTIONS);
@@ -4761,6 +4860,26 @@ static void load_vmcs12_host_state(struct
kvm_vcpu *vcpu,
vmcs_write32(GUEST_IDTR_LIMIT, 0xFFFF);
vmcs_write32(GUEST_GDTR_LIMIT, 0xFFFF);
+ if (nested_cpu_load_host_fred_state(vmcs12)) {
+ vmcs_write64(GUEST_IA32_FRED_CONFIG, vmcs12-
>host_ia32_fred_config);
+ vmcs_write64(GUEST_IA32_FRED_RSP1, vmcs12->host_ia32_fred_rsp1);
+ vmcs_write64(GUEST_IA32_FRED_RSP2, vmcs12->host_ia32_fred_rsp2);
+ vmcs_write64(GUEST_IA32_FRED_RSP3, vmcs12->host_ia32_fred_rsp3);
+ vmcs_write64(GUEST_IA32_FRED_STKLVLS, vmcs12-
>host_ia32_fred_stklvls);
+ vmcs_write64(GUEST_IA32_FRED_SSP1, vmcs12->host_ia32_fred_ssp1);
+ vmcs_write64(GUEST_IA32_FRED_SSP2, vmcs12->host_ia32_fred_ssp2);
+ vmcs_write64(GUEST_IA32_FRED_SSP3, vmcs12->host_ia32_fred_ssp3);
+ } else {
+ vmcs_write64(GUEST_IA32_FRED_CONFIG, vmx-
>nested.pre_vmexit_fred_config);
+ vmcs_write64(GUEST_IA32_FRED_RSP1, vmx-
>nested.pre_vmexit_fred_rsp1);
+ vmcs_write64(GUEST_IA32_FRED_RSP2, vmx-
>nested.pre_vmexit_fred_rsp2);
+ vmcs_write64(GUEST_IA32_FRED_RSP3, vmx-
>nested.pre_vmexit_fred_rsp3);
+ vmcs_write64(GUEST_IA32_FRED_STKLVLS, vmx-
>nested.pre_vmexit_fred_stklvls);
+ vmcs_write64(GUEST_IA32_FRED_SSP1, vmx-
>nested.pre_vmexit_fred_ssp1);
+ vmcs_write64(GUEST_IA32_FRED_SSP2, vmx-
>nested.pre_vmexit_fred_ssp2);
+ vmcs_write64(GUEST_IA32_FRED_SSP3, vmx-
>nested.pre_vmexit_fred_ssp3);
And this are actually nops. IOW, if I don't add this snippet of code,
the CPU still retains the guest FRED MSRs, i.e., using guest FRED state
from vmcs02 as that of vmcs01.
I confused myself. They are NOT nops, because __nested_vmx_vmexit()
switches from vmcs02 to vmcs01. The code should be (as the patch does):
__nested_vmx_vmexit()
{
...
/*
* Save guest FRED state of vmcs02 to nested.pre_vmexit_fred
* no matter if SECONDARY_VM_EXIT_SAVE_IA32_FRED is set.
*/
sync_vmcs02_to_vmcs12();
...
vmx_switch_vmcs();
...
/*
* Load nested.pre_vmexit_fred to guest FRED state of vmcs01
* if SECONDARY_VM_EXIT_LOAD_IA32_FRED is NOT set.
*/
load_vmcs12_host_state();
...
}
As not setting any of the two FRED VM-Exit controls are rare cases, we
need to add KVM tests with L1 that:
1) doesn't set SECONDARY_VM_EXIT_SAVE_IA32_FRED in VM-Exit controls.
2) doesn't set SECONDARY_VM_EXIT_LOAD_IA32_FRED in VM-Exit controls.
3) doesn't set both of the FRED VM-Exit controls.
Looks we need a framework for all VM-Exit controls which control whether
to save/load specific MSRs related to CPU features during VM-Exit?
