[PATCH v3 1/9] KVM: SVM: Initialize FRED VMCB fields

[Shivansh Dhiman]

The AMD FRED (Flexible Return and Event Delivery) feature introduces
several new fields to the VMCB save area. These fields include
FRED-specific stack pointers (fred_rsp[1-3], fred_ssp[1-3]), stack level
tracking (fred_stklvls), and configuration (fred_config), and the
control-area fields exit_int_data and event_inj_data. Note that
fred_rsp0 is only saved/restored for SEV-ES guests.

All FRED MSRs are zeroed on RESET. Reproduce the HW behavior here to
ensure that vCPU starts with a valid FRED state. Also update the size
of save areas of VMCB.

Co-developed-by: Neeraj Upadhyay <Neeraj.Upadhyay@xxxxxxx>
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@xxxxxxx>
Signed-off-by: Shivansh Dhiman <shivansh.dhiman@xxxxxxx>
Reviewed-by: Nikunj A Dadhania <nikunj@xxxxxxx>
---

Changes in v3:
* Update the fields and offsets of FRED MSRs according to the latest APM.
* Dropped fred_rsp0 from vmcb_save_area. Hardware doesn't save/restore
  it for non-SEV-ES guests. Move its handling to patch 3.
* Updated the commit message.

Changes in v2:
* Modified the zeroing of FRED MSRs from INIT to RESET and updated the commit
  message (Sean Christopherson).

---
 arch/x86/include/asm/svm.h | 31 ++++++++++++++++++++++++++++---
 arch/x86/kvm/svm/svm.c     | 11 +++++++++++
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index aa63431ba92c..0570581e251a 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -165,7 +165,10 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
 	u8 reserved_9[22];
 	u64 allowed_sev_features;	/* Offset 0x138 */
 	u64 guest_sev_features;		/* Offset 0x140 */
-	u8 reserved_10[664];
+	u8 reserved_10[40];
+	u64 exit_int_data;		/* Offset 0x170 */
+	u64 event_inj_data;
+	u8 reserved_11[608];
 	/*
 	 * Offset 0x3e0, 32 bytes reserved
 	 * for use by hypervisor/software.
@@ -370,6 +373,15 @@ struct vmcb_save_area {
 	u64 last_excp_to;
 	u8 reserved_0x298[72];
 	u64 spec_ctrl;		/* Guest version of SPEC_CTRL at 0x2E0 */
+	u8 reserved_0x2e8[1496];
+	u64 fred_rsp1;
+	u64 fred_rsp2;
+	u64 fred_rsp3;
+	u64 fred_stklvls;
+	u64 fred_ssp1;
+	u64 fred_ssp2;
+	u64 fred_ssp3;
+	u64 fred_config;
 } __packed;
 
 /* Save area definition for SEV-ES and SEV-SNP guests */
@@ -482,6 +494,18 @@ struct sev_es_save_area {
 	u8 fpreg_x87[80];
 	u8 fpreg_xmm[256];
 	u8 fpreg_ymm[256];
+	u8 reserved_0x670[568];
+	u64 guest_exit_int_data;
+	u64 guest_event_inj_data;
+	u64 fred_rsp0;
+	u64 fred_rsp1;
+	u64 fred_rsp2;
+	u64 fred_rsp3;
+	u64 fred_stklvls;
+	u64 fred_ssp1;
+	u64 fred_ssp2;
+	u64 fred_ssp3;
+	u64 fred_config;
 } __packed;
 
 struct ghcb_save_area {
@@ -552,9 +576,9 @@ struct vmcb {
 	};
 } __packed;
 
-#define EXPECTED_VMCB_SAVE_AREA_SIZE		744
+#define EXPECTED_VMCB_SAVE_AREA_SIZE		2304
 #define EXPECTED_GHCB_SAVE_AREA_SIZE		1032
-#define EXPECTED_SEV_ES_SAVE_AREA_SIZE		1648
+#define EXPECTED_SEV_ES_SAVE_AREA_SIZE		2304
 #define EXPECTED_VMCB_CONTROL_AREA_SIZE		1024
 #define EXPECTED_GHCB_SIZE			PAGE_SIZE
 
@@ -578,6 +602,7 @@ static inline void __unused_size_checks(void)
 	BUILD_BUG_RESERVED_OFFSET(vmcb_save_area, 0x180);
 	BUILD_BUG_RESERVED_OFFSET(vmcb_save_area, 0x248);
 	BUILD_BUG_RESERVED_OFFSET(vmcb_save_area, 0x298);
+	BUILD_BUG_RESERVED_OFFSET(vmcb_save_area, 0x2e8);
 
 	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0xc8);
 	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0xcc);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index dd19c7b4e904..6d55b0a576d9 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1217,6 +1217,17 @@ static void init_vmcb(struct kvm_vcpu *vcpu, bool init_event)
 	save->idtr.base = 0;
 	save->idtr.limit = 0xffff;
 
+	if (!init_event) {
+		save->fred_rsp1 = 0;
+		save->fred_rsp2 = 0;
+		save->fred_rsp3 = 0;
+		save->fred_stklvls = 0;
+		save->fred_ssp1 = 0;
+		save->fred_ssp2 = 0;
+		save->fred_ssp3 = 0;
+		save->fred_config = 0;
+	}
+
 	init_sys_seg(&save->ldtr, SEG_TYPE_LDT);
 	init_sys_seg(&save->tr, SEG_TYPE_BUSY_TSS16);
 
-- 
2.43.0