[PATCH v4 3/3] arm64: kvm: inject SError with user space specified syndrome

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when SError happen, kvm notifies user space to record the CPER,
user space specifies and passes the contents of ESR_EL1 on taking
a virtual SError interrupt to KVM, KVM enables virtual system
error or asynchronous abort with this specifies syndrome. This
patch modify the world-switch to restore VSESR_EL2, VSESR_EL2
saves the virtual SError syndrome, it becomes the ESR_EL1 value when
HCR_EL2.VSE injects an SError. This register is added by the
RAS Extensions.

Changes since v3:
(1) Move restore VSESR_EL2 value logic to a helper method
(2) In the world-switch, not save VSESR_EL2, because no one cares the
    old VSESR_EL2 value
(3) Add a new KVM_ARM_SEI ioctl to set the VSESR_EL2 value and pend
    a virtual system error

Signed-off-by: Dongjiu Geng <gengdongjiu@xxxxxxxxxx>
Signed-off-by: Quanming Wu <wuquanming@xxxxxxxxxx>
---
 Documentation/virtual/kvm/api.txt    | 10 ++++++++++
 arch/arm/include/asm/kvm_host.h      |  1 +
 arch/arm/kvm/arm.c                   |  7 +++++++
 arch/arm/kvm/guest.c                 |  5 +++++
 arch/arm64/include/asm/esr.h         |  2 ++
 arch/arm64/include/asm/kvm_emulate.h | 10 ++++++++++
 arch/arm64/include/asm/kvm_host.h    |  2 ++
 arch/arm64/include/asm/sysreg.h      |  3 +++
 arch/arm64/kvm/guest.c               | 14 ++++++++++++++
 arch/arm64/kvm/handle_exit.c         | 25 +++++++++++++++++++------
 arch/arm64/kvm/hyp/switch.c          | 14 ++++++++++++++
 include/uapi/linux/kvm.h             |  8 ++++++++
 12 files changed, 95 insertions(+), 6 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 3c248f7..852ac55 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3377,6 +3377,16 @@ struct kvm_ppc_resize_hpt {
 	__u32 pad;
 };
 
+4.104 KVM_ARM_SEI
+
+Capability: KVM_EXIT_SERROR_INTR
+Architectures: arm/arm64
+Type: vcpu ioctl
+Parameters: u64 (syndrome)
+Returns: 0 in case of success
+
+Pend an virtual system error or asynchronous abort with user space specified.
+
 5. The kvm_run structure
 ------------------------
 
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 31ee468..566292a 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -244,6 +244,7 @@ int kvm_arm_coproc_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *);
 
 int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
 		int exception_index);
+int kvm_vcpu_ioctl_sei(struct kvm_vcpu *vcpu, u64 *syndrome);
 
 static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr,
 				       unsigned long hyp_stack_ptr,
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 96dba7c..583294f 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -987,6 +987,13 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 			return -EFAULT;
 		return kvm_arm_vcpu_has_attr(vcpu, &attr);
 	}
+	case KVM_ARM_SEI: {
+		u64 syndrome;
+
+		if (copy_from_user(&syndrome, argp, sizeof(syndrome)))
+			return -EFAULT;
+		return kvm_vcpu_ioctl_sei(vcpu, &syndrome);
+	}
 	default:
 		return -EINVAL;
 	}
diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c
index fa6182a..72505bf 100644
--- a/arch/arm/kvm/guest.c
+++ b/arch/arm/kvm/guest.c
@@ -248,6 +248,11 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
 	return -EINVAL;
 }
 
+int kvm_vcpu_ioctl_sei(struct kvm_vcpu *vcpu, u64 *syndrome)
+{
+	return 0;
+}
+
 int __attribute_const__ kvm_target_cpu(void)
 {
 	switch (read_cpuid_part()) {
diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 22f9c90..d009c99 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -127,6 +127,8 @@
 #define ESR_ELx_WFx_ISS_WFE	(UL(1) << 0)
 #define ESR_ELx_xVC_IMM_MASK	((1UL << 16) - 1)
 
+#define VSESR_ELx_IDS_ISS_MASK    ((1UL << 25) - 1)
+
 /* ESR value templates for specific events */
 
 /* BRK instruction trap from AArch64 state */
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 5f64ab2..93dc3d1 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -155,6 +155,16 @@ static inline u32 kvm_vcpu_get_hsr(const struct kvm_vcpu *vcpu)
 	return vcpu->arch.fault.esr_el2;
 }
 
+static inline u32 kvm_vcpu_get_vsesr(const struct kvm_vcpu *vcpu)
+{
+		return vcpu->arch.fault.vsesr_el2;
+}
+
+static inline void kvm_vcpu_set_vsesr(struct kvm_vcpu *vcpu, unsigned long val)
+{
+		vcpu->arch.fault.vsesr_el2 = val;
+}
+
 static inline int kvm_vcpu_get_condition(const struct kvm_vcpu *vcpu)
 {
 	u32 esr = kvm_vcpu_get_hsr(vcpu);
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index e7705e7..b6242fb 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -86,6 +86,7 @@ struct kvm_vcpu_fault_info {
 	u32 esr_el2;		/* Hyp Syndrom Register */
 	u64 far_el2;		/* Hyp Fault Address Register */
 	u64 hpfar_el2;		/* Hyp IPA Fault Address Register */
+	u32 vsesr_el2;		/* Virtual SError Exception Syndrome Register */
 };
 
 /*
@@ -385,6 +386,7 @@ int kvm_arm_vcpu_arch_get_attr(struct kvm_vcpu *vcpu,
 			       struct kvm_device_attr *attr);
 int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
 			       struct kvm_device_attr *attr);
+int kvm_vcpu_ioctl_sei(struct kvm_vcpu *vcpu, u64 *syndrome);
 
 static inline void __cpu_init_stage2(void)
 {
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 32964c7..3af6907 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -125,6 +125,9 @@
 #define REG_PSTATE_PAN_IMM		sys_reg(0, 0, 4, 0, 4)
 #define REG_PSTATE_UAO_IMM		sys_reg(0, 0, 4, 0, 3)
 
+/* virtual SError exception syndrome register in armv8.2 */
+#define REG_VSESR_EL2			sys_reg(3, 4, 5, 2, 3)
+
 #define SET_PSTATE_PAN(x) __emit_inst(0xd5000000 | REG_PSTATE_PAN_IMM |	\
 				      (!!x)<<8 | 0x1f)
 #define SET_PSTATE_UAO(x) __emit_inst(0xd5000000 | REG_PSTATE_UAO_IMM |	\
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index b37446a..21c20b0 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -277,6 +277,20 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
 	return -EINVAL;
 }
 
+int kvm_vcpu_ioctl_sei(struct kvm_vcpu *vcpu, u64 *syndrome)
+{
+	u64 reg = *syndrome;
+
+	if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN) && reg)
+		/* set vsesr_el2[24:0] with value that user space specified */
+		kvm_vcpu_set_vsesr(vcpu, reg & VSESR_ELx_IDS_ISS_MASK);
+
+	/* inject virtual system Error or asynchronous abort */
+	kvm_inject_vabt(vcpu);
+
+	return 0;
+}
+
 int __attribute_const__ kvm_target_cpu(void)
 {
 	unsigned long implementor = read_cpuid_implementor();
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index c89d83a..23c02c2 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -180,7 +180,11 @@ static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
 
 static int kvm_handle_guest_sei(struct kvm_vcpu *vcpu, struct kvm_run *run)
 {
-	unsigned long fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
+	unsigned long hva, fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
+	struct kvm_memory_slot *memslot;
+	int hsr, ret = 1;
+	bool writable;
+	gfn_t gfn;
 
 	if (handle_guest_sei((unsigned long)fault_ipa,
 				kvm_vcpu_get_hsr(vcpu))) {
@@ -190,9 +194,20 @@ static int kvm_handle_guest_sei(struct kvm_vcpu *vcpu, struct kvm_run *run)
 				(unsigned long)kvm_vcpu_get_hsr(vcpu));
 
 		kvm_inject_vabt(vcpu);
+	} else {
+		hsr = kvm_vcpu_get_hsr(vcpu);
+
+		gfn = fault_ipa >> PAGE_SHIFT;
+		memslot = gfn_to_memslot(vcpu->kvm, gfn);
+		hva = gfn_to_hva_memslot_prot(memslot, gfn, &writable);
+
+		run->exit_reason = KVM_EXIT_SERROR_INTR;
+		run->serror_intr.syndrome_info = hsr;
+		run->serror_intr.address = hva;
+		ret = 0;
 	}
 
-	return 0;
+	return ret;
 }
 
 /*
@@ -218,8 +233,7 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
 			*vcpu_pc(vcpu) -= adj;
 		}
 
-		kvm_handle_guest_sei(vcpu, run);
-		return 1;
+		return kvm_handle_guest_sei(vcpu, run);
 	}
 
 	exception_index = ARM_EXCEPTION_CODE(exception_index);
@@ -228,8 +242,7 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
 	case ARM_EXCEPTION_IRQ:
 		return 1;
 	case ARM_EXCEPTION_EL1_SERROR:
-		kvm_handle_guest_sei(vcpu, run);
-		return 1;
+		return kvm_handle_guest_sei(vcpu, run);
 	case ARM_EXCEPTION_TRAP:
 		/*
 		 * See ARM ARM B1.14.1: "Hyp traps on instructions
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index aede165..6d17c97 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -67,6 +67,13 @@ static hyp_alternate_select(__activate_traps_arch,
 			    __activate_traps_nvhe, __activate_traps_vhe,
 			    ARM64_HAS_VIRT_HOST_EXTN);
 
+static void __hyp_text __sysreg_set_vsesr(struct kvm_vcpu *vcpu)
+{
+	if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN) &&
+			(vcpu->arch.hcr_el2 & HCR_VSE))
+		write_sysreg_s(vcpu->arch.fault.vsesr_el2, REG_VSESR_EL2);
+}
+
 static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
 {
 	u64 val;
@@ -86,6 +93,13 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
 		isb();
 	}
 	write_sysreg(val, hcr_el2);
+
+	/*
+	 * If the virtual SError interrupt is taken to EL1 using AArch64,
+	 * then VSESR_EL2 provides the syndrome value reported in ESR_EL1.
+	 */
+	__sysreg_set_vsesr(vcpu);
+
 	/* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
 	write_sysreg(1 << 15, hstr_el2);
 	/*
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 27fe556..ab91fe3 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -205,6 +205,7 @@ struct kvm_hyperv_exit {
 #define KVM_EXIT_S390_STSI        25
 #define KVM_EXIT_IOAPIC_EOI       26
 #define KVM_EXIT_HYPERV           27
+#define KVM_EXIT_SERROR_INTR      28
 
 /* For KVM_EXIT_INTERNAL_ERROR */
 /* Emulate instruction failed. */
@@ -360,6 +361,11 @@ struct kvm_run {
 		struct {
 			__u8 vector;
 		} eoi;
+		/* KVM_EXIT_SERROR_INTR */
+		struct {
+			__u32 syndrome_info;
+			__u64 address;
+		} serror_intr;
 		/* KVM_EXIT_HYPERV */
 		struct kvm_hyperv_exit hyperv;
 		/* Fix the size of the union. */
@@ -1301,6 +1307,8 @@ struct kvm_s390_ucas_mapping {
 #define KVM_S390_GET_IRQ_STATE	  _IOW(KVMIO, 0xb6, struct kvm_s390_irq_state)
 /* Available with KVM_CAP_X86_SMM */
 #define KVM_SMI                   _IO(KVMIO,   0xb7)
+/* Available with KVM_EXIT_SERROR_INTR */
+#define KVM_ARM_SEI               _IO(KVMIO,   0xb8)
 
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
 #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
-- 
2.10.1

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