[PATCH v9 6/7] arm64: kvm: Set Virtual SError Exception Syndrome for guest

[Dongjiu Geng]

RAS Extension add a VSESR_EL2 register which can provide
the syndrome value reported to software on taking a virtual
SError interrupt exception. This patch supports to specify
this Syndrome.

In the RAS Extensions we can not set all-zero syndrome value
for SError, which means 'RAS error: Uncategorized' instead of
'no valid ISS'. So set it to IMPLEMENTATION DEFINED syndrome
by default.

We also need to support userspace to specify a valid syndrome
value, Because in some case, the recovery is driven by userspace.
This patch can support that userspace specify it.

In the guest/host world switch, restore this value to VSESR_EL2
only when HCR_EL2.VSE is set. This value no need to be saved
because it is stale vale when guest exit.

Signed-off-by: Dongjiu Geng <gengdongjiu@xxxxxxxxxx>
[Set an impdef ESR for Virtual-SError]
Signed-off-by: James Morse <james.morse@xxxxxxx>
---
 arch/arm64/include/asm/kvm_emulate.h | 10 ++++++++++
 arch/arm64/include/asm/kvm_host.h    |  1 +
 arch/arm64/include/asm/sysreg.h      |  3 +++
 arch/arm64/kvm/guest.c               | 11 ++++++++++-
 arch/arm64/kvm/hyp/switch.c          | 16 ++++++++++++++++
 arch/arm64/kvm/inject_fault.c        | 13 ++++++++++++-
 6 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 555b28b..73c84d0 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 769cc58..53d1d81 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -88,6 +88,7 @@ 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 */
 };
 
 /*
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 47b967d..3b035cc 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -86,6 +86,9 @@
 #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 */
+#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 738ae90..ffad42b 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -279,7 +279,16 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
 
 int kvm_arm_set_sei_esr(struct kvm_vcpu *vcpu, u32 *syndrome)
 {
-	return -EINVAL;
+	u64 reg = *syndrome;
+
+	/* inject virtual system Error or asynchronous abort */
+	kvm_inject_vabt(vcpu);
+
+	if (reg)
+		/* set vsesr_el2[24:0] with value that user space specified */
+		kvm_vcpu_set_vsesr(vcpu, reg & ESR_ELx_ISS_MASK);
+
+	return 0;
 }
 
 int __attribute_const__ kvm_target_cpu(void)
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index fb5a538..7f08a5d 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -67,6 +67,14 @@ 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, u64 value)
+{
+	if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN) &&
+			       (value & HCR_VSE))
+		write_sysreg_s(kvm_vcpu_get_vsesr(vcpu), REG_VSESR_EL2);
+}
+
+
 static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
 {
 	u64 val;
@@ -86,6 +94,14 @@ 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 ISS field
+	 * of ESR_EL1.
+	 */
+	__sysreg_set_vsesr(vcpu, val);
+
 	/* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
 	write_sysreg(1 << 15, hstr_el2);
 	/*
diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
index 3556715..fb94b5e 100644
--- a/arch/arm64/kvm/inject_fault.c
+++ b/arch/arm64/kvm/inject_fault.c
@@ -246,14 +246,25 @@ void kvm_inject_undefined(struct kvm_vcpu *vcpu)
 		inject_undef64(vcpu);
 }
 
+static void pend_guest_serror(struct kvm_vcpu *vcpu, u64 esr)
+{
+	kvm_vcpu_set_vsesr(vcpu, esr);
+	vcpu_set_hcr(vcpu, vcpu_get_hcr(vcpu) | HCR_VSE);
+}
+
 /**
  * kvm_inject_vabt - inject an async abort / SError into the guest
  * @vcpu: The VCPU to receive the exception
  *
  * It is assumed that this code is called from the VCPU thread and that the
  * VCPU therefore is not currently executing guest code.
+ *
+ * Systems with the RAS Extensions specify an imp-def ESR (ISV/IDS = 1) with
+ * the remaining ISS all-zeros so that this error is not interpreted as an
+ * uncatagorized RAS error. Without the RAS Extensions we can't specify an ESR
+ * value, so the CPU generates an imp-def value.
  */
 void kvm_inject_vabt(struct kvm_vcpu *vcpu)
 {
-	vcpu_set_hcr(vcpu, vcpu_get_hcr(vcpu) | HCR_VSE);
+	pend_guest_serror(vcpu, ESR_ELx_ISV);
 }
-- 
1.9.1