diff mbox series

[v4,05/19] KVM: VMX: Initialize VMCS FRED fields

Message ID 20250328171205.2029296-6-xin@zytor.com (mailing list archive)
State New
Headers show
Series Enable FRED with KVM VMX | expand

Commit Message

Xin Li (Intel) March 28, 2025, 5:11 p.m. UTC 
From: Xin Li <xin3.li@intel.com>

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

FRED CPU state is managed in 9 new FRED MSRs:
        IA32_FRED_CONFIG,
        IA32_FRED_STKLVLS,
        IA32_FRED_RSP0,
        IA32_FRED_RSP1,
        IA32_FRED_RSP2,
        IA32_FRED_RSP3,
        IA32_FRED_SSP1,
        IA32_FRED_SSP2,
        IA32_FRED_SSP3,
as well as a few existing CPU registers and MSRs:
        CR4.FRED,
        IA32_STAR,
        IA32_KERNEL_GS_BASE,
        IA32_PL0_SSP (also known as IA32_FRED_SSP0).

CR4, IA32_KERNEL_GS_BASE and IA32_STAR are already well managed.
Except IA32_FRED_RSP0 and IA32_FRED_SSP0, all other FRED CPU state
MSRs have corresponding VMCS fields in both the host-state and
guest-state areas.  So KVM just needs to initialize them, and with
proper VM entry/exit FRED controls, a FRED CPU will keep tracking
host and guest FRED CPU state in VMCS automatically.

Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Tested-by: Shan Kang <shan.kang@intel.com>
---

Change in v4:
* Initialize host SSP[1-3] to 0s in vmx_set_constant_host_state()
  because Linux doesn't support kernel shadow stacks (Chao Gao).

Change in v3:
* Use structure kvm_host_values to keep host fred config & stack levels
  (Sean Christopherson).

Changes in v2:
* Use kvm_cpu_cap_has() instead of cpu_feature_enabled() to decouple
  KVM's capability to virtualize a feature and host's enabling of a
  feature (Chao Gao).
* Move guest FRED state init into __vmx_vcpu_reset() (Chao Gao).
---
 arch/x86/include/asm/vmx.h | 32 ++++++++++++++++++++++++++++++++
 arch/x86/kvm/vmx/vmx.c     | 36 ++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/x86.h         |  3 +++
 3 files changed, 71 insertions(+)
diff mbox series

Patch

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 5598517617a5..8a2b097aadf2 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -289,12 +289,44 @@  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_CONFIG_HIGH	= 0x0000281b,
+	GUEST_IA32_FRED_RSP1		= 0x0000281c,
+	GUEST_IA32_FRED_RSP1_HIGH	= 0x0000281d,
+	GUEST_IA32_FRED_RSP2		= 0x0000281e,
+	GUEST_IA32_FRED_RSP2_HIGH	= 0x0000281f,
+	GUEST_IA32_FRED_RSP3		= 0x00002820,
+	GUEST_IA32_FRED_RSP3_HIGH	= 0x00002821,
+	GUEST_IA32_FRED_STKLVLS		= 0x00002822,
+	GUEST_IA32_FRED_STKLVLS_HIGH	= 0x00002823,
+	GUEST_IA32_FRED_SSP1		= 0x00002824,
+	GUEST_IA32_FRED_SSP1_HIGH	= 0x00002825,
+	GUEST_IA32_FRED_SSP2		= 0x00002826,
+	GUEST_IA32_FRED_SSP2_HIGH	= 0x00002827,
+	GUEST_IA32_FRED_SSP3		= 0x00002828,
+	GUEST_IA32_FRED_SSP3_HIGH	= 0x00002829,
 	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_CONFIG_HIGH	= 0x00002c09,
+	HOST_IA32_FRED_RSP1		= 0x00002c0a,
+	HOST_IA32_FRED_RSP1_HIGH	= 0x00002c0b,
+	HOST_IA32_FRED_RSP2		= 0x00002c0c,
+	HOST_IA32_FRED_RSP2_HIGH	= 0x00002c0d,
+	HOST_IA32_FRED_RSP3		= 0x00002c0e,
+	HOST_IA32_FRED_RSP3_HIGH	= 0x00002c0f,
+	HOST_IA32_FRED_STKLVLS		= 0x00002c10,
+	HOST_IA32_FRED_STKLVLS_HIGH	= 0x00002c11,
+	HOST_IA32_FRED_SSP1		= 0x00002c12,
+	HOST_IA32_FRED_SSP1_HIGH	= 0x00002c13,
+	HOST_IA32_FRED_SSP2		= 0x00002c14,
+	HOST_IA32_FRED_SSP2_HIGH	= 0x00002c15,
+	HOST_IA32_FRED_SSP3		= 0x00002c16,
+	HOST_IA32_FRED_SSP3_HIGH	= 0x00002c17,
 	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 ab84939ace96..ac6aa2d091c3 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1505,6 +1505,15 @@  void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu,
 				    (unsigned long)(cpu_entry_stack(cpu) + 1));
 		}
 
+		/* Per-CPU FRED MSRs */
+		if (kvm_cpu_cap_has(X86_FEATURE_FRED)) {
+#ifdef CONFIG_X86_64
+			vmcs_write64(HOST_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB));
+			vmcs_write64(HOST_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI));
+			vmcs_write64(HOST_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF));
+#endif
+		}
+
 		vmx->loaded_vmcs->cpu = cpu;
 	}
 }
@@ -4388,6 +4397,17 @@  void vmx_set_constant_host_state(struct vcpu_vmx *vmx)
 	 */
 	vmcs_write16(HOST_DS_SELECTOR, 0);
 	vmcs_write16(HOST_ES_SELECTOR, 0);
+
+	if (kvm_cpu_cap_has(X86_FEATURE_FRED)) {
+		/* FRED CONFIG and STKLVLS are the same on all CPUs */
+		vmcs_write64(HOST_IA32_FRED_CONFIG, kvm_host.fred_config);
+		vmcs_write64(HOST_IA32_FRED_STKLVLS, kvm_host.fred_stklvls);
+
+		/* Linux doesn't support kernel shadow stacks, thus SSPs are 0s */
+		vmcs_write64(HOST_IA32_FRED_SSP1, 0);
+		vmcs_write64(HOST_IA32_FRED_SSP2, 0);
+		vmcs_write64(HOST_IA32_FRED_SSP3, 0);
+	}
 #else
 	vmcs_write16(HOST_DS_SELECTOR, __KERNEL_DS);  /* 22.2.4 */
 	vmcs_write16(HOST_ES_SELECTOR, __KERNEL_DS);  /* 22.2.4 */
@@ -4889,6 +4909,17 @@  static void init_vmcs(struct vcpu_vmx *vmx)
 	}
 
 	vmx_setup_uret_msrs(vmx);
+
+	if (kvm_cpu_cap_has(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);
+	}
 }
 
 static void __vmx_vcpu_reset(struct kvm_vcpu *vcpu)
@@ -8705,6 +8736,11 @@  __init int vmx_hardware_setup(void)
 
 	kvm_set_posted_intr_wakeup_handler(pi_wakeup_handler);
 
+	if (kvm_cpu_cap_has(X86_FEATURE_FRED)) {
+		rdmsrl(MSR_IA32_FRED_CONFIG, kvm_host.fred_config);
+		rdmsrl(MSR_IA32_FRED_STKLVLS, kvm_host.fred_stklvls);
+	}
+
 	return r;
 }
 
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 9dc32a409076..02514f5b9c0b 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -46,6 +46,9 @@  struct kvm_host_values {
 	u64 xcr0;
 	u64 xss;
 	u64 arch_capabilities;
+
+	u64 fred_config;
+	u64 fred_stklvls;
 };
 
 void kvm_spurious_fault(void);