On Thu, 20 May 2021 13:55:48 +0100,
Zenghui Yu [off-list ref] wrote:

On 2021/5/11 0:58, Marc Zyngier wrote:

quoted

From: Jintack Lim <redacted>

Support injecting exceptions and performing exception returns to and
from virtual EL2.  This must be done entirely in software except when
taking an exception from vEL0 to vEL2 when the virtual HCR_EL2.{E2H,TGE}
== {1,1}  (a VHE guest hypervisor).

Signed-off-by: Jintack Lim <redacted>
Signed-off-by: Christoffer Dall <redacted>
[maz: switch to common exception injection framework]
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_arm.h     |  17 +++
 arch/arm64/include/asm/kvm_emulate.h |  10 ++
 arch/arm64/kvm/Makefile              |   2 +-
 arch/arm64/kvm/emulate-nested.c      | 176 +++++++++++++++++++++++++++
 arch/arm64/kvm/hyp/exception.c       |  45 +++++--
 arch/arm64/kvm/inject_fault.c        |  63 ++++++++--
 arch/arm64/kvm/trace_arm.h           |  59 +++++++++
 7 files changed, 354 insertions(+), 18 deletions(-)
 create mode 100644 arch/arm64/kvm/emulate-nested.c

[...]

quoted

 static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr)
 {
 	unsigned long cpsr = *vcpu_cpsr(vcpu);
 	bool is_aarch32 = vcpu_mode_is_32bit(vcpu);
 	u32 esr = 0;
 -	vcpu->arch.flags |= (KVM_ARM64_EXCEPT_AA64_EL1		|
-			     KVM_ARM64_EXCEPT_AA64_ELx_SYNC	|
-			     KVM_ARM64_PENDING_EXCEPTION);
-
-	vcpu_write_sys_reg(vcpu, addr, FAR_EL1);
+	pend_sync_exception(vcpu);
  	/*
 	 * Build an {i,d}abort, depending on the level and the

@@ -45,16 +79,22 @@ static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr
 	if (!is_iabt)
 		esr |= ESR_ELx_EC_DABT_LOW << ESR_ELx_EC_SHIFT;
 -	vcpu_write_sys_reg(vcpu, esr | ESR_ELx_FSC_EXTABT, ESR_EL1);
+	esr |= ESR_ELx_FSC_EXTABT;
+
+	if (vcpu->arch.flags & KVM_ARM64_EXCEPT_AA64_EL1) {

This isn't the right way to pick between EL1 and EL2 since
KVM_ARM64_EXCEPT_AA64_EL1 is (0 << 11), we will not be able
to inject abort to EL1 that way.

Indeed, well observed. I'm squashing the following fix in this patch.

Thanks,

	M.

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 27397ecf9a23..fe781557e42c 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h

@@ -524,6 +524,7 @@ struct kvm_vcpu_arch {
 #define KVM_ARM64_EXCEPT_AA64_ELx_SERR	(3 << 9)
 #define KVM_ARM64_EXCEPT_AA64_EL1	(0 << 11)
 #define KVM_ARM64_EXCEPT_AA64_EL2	(1 << 11)
+#define KVM_ARM64_EXCEPT_AA64_EL_MASK	(1 << 11)
 
 /*
  * Overlaps with KVM_ARM64_EXCEPT_MASK on purpose so that it can't be

diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
index 06df0bb848ca..5dcf3f8b08b8 100644
--- a/arch/arm64/kvm/inject_fault.c
+++ b/arch/arm64/kvm/inject_fault.c

@@ -52,6 +52,11 @@ static void pend_sync_exception(struct kvm_vcpu *vcpu)
 	}
 }
 
+static bool match_target_el(struct kvm_vcpu *vcpu, unsigned long target)
+{
+	return (vcpu->arch.flags & KVM_ARM64_EXCEPT_AA64_EL_MASK) == target;
+}
+
 static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr)
 {
 	unsigned long cpsr = *vcpu_cpsr(vcpu);

@@ -81,7 +86,7 @@ static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr
 
 	esr |= ESR_ELx_FSC_EXTABT;
 
-	if (vcpu->arch.flags & KVM_ARM64_EXCEPT_AA64_EL1) {
+	if (match_target_el(vcpu, KVM_ARM64_EXCEPT_AA64_EL1)) {
 		vcpu_write_sys_reg(vcpu, addr, FAR_EL1);
 		vcpu_write_sys_reg(vcpu, esr, ESR_EL1);
 	} else {

@@ -103,7 +108,7 @@ static void inject_undef64(struct kvm_vcpu *vcpu)
 	if (kvm_vcpu_trap_il_is32bit(vcpu))
 		esr |= ESR_ELx_IL;
 
-	if (vcpu->arch.flags & KVM_ARM64_EXCEPT_AA64_EL1)
+	if (match_target_el(vcpu, KVM_ARM64_EXCEPT_AA64_EL1))
 		vcpu_write_sys_reg(vcpu, esr, ESR_EL1);
 	else
 		vcpu_write_sys_reg(vcpu, esr, ESR_EL2);

-- 
Without deviation from the norm, progress is not possible.

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