[PATCH v1 08/23] KVM: VMX: Initialize VMCS FRED fields

Xin Li
2023-11-08T19:00:29Z

Initialize host VMCS FRED fields with host FRED MSRs' value and
guest VMCS FRED fields to 0.

FRED CPU states are managed in 9 new FRED MSRs, as well as a few
existing CPU registers and MSRs, e.g., CR4.FRED. To support FRED
context management, new VMCS fields corresponding to most of FRED
CPU state MSRs are added to both the host-state and guest-state
areas of VMCS.

Specifically no VMCS fields are added for FRED RSP0 and SSP0 MSRs,
because the 2 FRED MSRs are used during ring 3 event delivery only,
thus KVM, running on ring 0, can run safely even with guest FRED
RSP0 and SSP0. It can be deferred to load host FRED RSP0 and SSP0
until before returning to user level.

Tested-by: Shan Kang <shan.kang@intel.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
---
arch/x86/include/asm/vmx.h | 16 ++++++++++++++++
arch/x86/kvm/vmx/vmx.c | 32 ++++++++++++++++++++++++++++++++
2 files changed, 48 insertions(+)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 41796a733bc9..d54a1a1057b0 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -277,12 +277,28 @@ enum vmcs_field {
GUEST_BNDCFGS_HIGH = 0x00002813,
GUEST_IA32_RTIT_CTL = 0x00002814,
GUEST_IA32_RTIT_CTL_HIGH = 0x00002815,
+ GUEST_IA32_FRED_CONFIG = 0x0000281a,
+ GUEST_IA32_FRED_RSP1 = 0x0000281c,
+ GUEST_IA32_FRED_RSP2 = 0x0000281e,
+ GUEST_IA32_FRED_RSP3 = 0x00002820,
+ GUEST_IA32_FRED_STKLVLS = 0x00002822,
+ GUEST_IA32_FRED_SSP1 = 0x00002824,
+ GUEST_IA32_FRED_SSP2 = 0x00002826,
+ GUEST_IA32_FRED_SSP3 = 0x00002828,
HOST_IA32_PAT = 0x00002c00,
HOST_IA32_PAT_HIGH = 0x00002c01,
HOST_IA32_EFER = 0x00002c02,
HOST_IA32_EFER_HIGH = 0x00002c03,
HOST_IA32_PERF_GLOBAL_CTRL = 0x00002c04,
HOST_IA32_PERF_GLOBAL_CTRL_HIGH = 0x00002c05,
+ HOST_IA32_FRED_CONFIG = 0x00002c08,
+ HOST_IA32_FRED_RSP1 = 0x00002c0a,
+ HOST_IA32_FRED_RSP2 = 0x00002c0c,
+ HOST_IA32_FRED_RSP3 = 0x00002c0e,
+ HOST_IA32_FRED_STKLVLS = 0x00002c10,
+ HOST_IA32_FRED_SSP1 = 0x00002c12,
+ HOST_IA32_FRED_SSP2 = 0x00002c14,
+ HOST_IA32_FRED_SSP3 = 0x00002c16,
PIN_BASED_VM_EXEC_CONTROL = 0x00004000,
CPU_BASED_VM_EXEC_CONTROL = 0x00004002,
EXCEPTION_BITMAP = 0x00004004,
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 327e052d90c1..41772ecdd368 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1477,6 +1477,18 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu,
(unsigned long)(cpu_entry_stack(cpu) + 1));
}

+#ifdef CONFIG_X86_64
+ /* Per-CPU FRED MSRs */
+ if (cpu_feature_enabled(X86_FEATURE_FRED)) {
+ vmcs_write64(HOST_IA32_FRED_RSP1, read_msr(MSR_IA32_FRED_RSP1));
+ vmcs_write64(HOST_IA32_FRED_RSP2, read_msr(MSR_IA32_FRED_RSP2));
+ vmcs_write64(HOST_IA32_FRED_RSP3, read_msr(MSR_IA32_FRED_RSP3));
+ vmcs_write64(HOST_IA32_FRED_SSP1, read_msr(MSR_IA32_FRED_SSP1));
+ vmcs_write64(HOST_IA32_FRED_SSP2, read_msr(MSR_IA32_FRED_SSP2));
+ vmcs_write64(HOST_IA32_FRED_SSP3, read_msr(MSR_IA32_FRED_SSP3));
+ }
+#endif
+
vmx->loaded_vmcs->cpu = cpu;
}
}
@@ -4375,6 +4387,15 @@ void vmx_set_constant_host_state(struct vcpu_vmx *vmx)

if (cpu_has_load_ia32_efer())
vmcs_write64(HOST_IA32_EFER, host_efer);
+
+ /*
+ * FRED MSRs are per-cpu, however FRED CONFIG and STKLVLS MSRs
+ * are the same on all CPUs, thus they are initialized here.
+ */
+ if (cpu_feature_enabled(X86_FEATURE_FRED)) {
+ vmcs_write64(HOST_IA32_FRED_CONFIG, read_msr(MSR_IA32_FRED_CONFIG));
+ vmcs_write64(HOST_IA32_FRED_STKLVLS, read_msr(MSR_IA32_FRED_STKLVLS));
+ }
}

void set_cr4_guest_host_mask(struct vcpu_vmx *vmx)
@@ -4936,6 +4957,17 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
vmcs_writel(GUEST_IDTR_BASE, 0);
vmcs_write32(GUEST_IDTR_LIMIT, 0xffff);

+ if (cpu_feature_enabled(X86_FEATURE_FRED)) {
+ vmcs_write64(GUEST_IA32_FRED_CONFIG, 0);
+ vmcs_write64(GUEST_IA32_FRED_RSP1, 0);
+ vmcs_write64(GUEST_IA32_FRED_RSP2, 0);
+ vmcs_write64(GUEST_IA32_FRED_RSP3, 0);
+ vmcs_write64(GUEST_IA32_FRED_STKLVLS, 0);
+ vmcs_write64(GUEST_IA32_FRED_SSP1, 0);
+ vmcs_write64(GUEST_IA32_FRED_SSP2, 0);
+ vmcs_write64(GUEST_IA32_FRED_SSP3, 0);
+ }
+
vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE);
vmcs_write32(GUEST_INTERRUPTIBILITY_INFO, 0);
vmcs_writel(GUEST_PENDING_DBG_EXCEPTIONS, 0);
--
2.42.0