[PATCH v5 09/15] KVM: arm64: Handle HDBSS faults

[Tian Zheng]

From: Eillon <yezhenyu2@xxxxxxxxxx>

Once the buffer is full, hardware stops promoting writable-clean
descriptors and raises a stage-2 Permission fault with
ESR_EL2.ISS2.HDBSSF instead. Failed HDBSS accesses, such as external
aborts and granule protection faults, are reported the same way.

Dispatch from kvm_handle_guest_abort() via the new esr_iss2_is_hdbssf()
helper. FSC == OK means the exit path already flushed, so resume the
guest; any other FSC is an error - clear it and report -EFAULT.

Signed-off-by: Eillon <yezhenyu2@xxxxxxxxxx>
Signed-off-by: Tian Zheng <zhengtian10@xxxxxxxxxx>
---
 arch/arm64/include/asm/esr.h           |  5 +++++
 arch/arm64/include/asm/kvm_dirty_bit.h |  1 +
 arch/arm64/kvm/dirty_bit.c             | 29 ++++++++++++++++++++++++++
 arch/arm64/kvm/mmu.c                   |  4 ++++
 4 files changed, 39 insertions(+)

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index f816f5d77f1a..4b3ccd407faa 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -437,6 +437,11 @@
 #ifndef __ASSEMBLER__
 #include <asm/types.h>

+static inline bool esr_iss2_is_hdbssf(unsigned long esr)
+{
+	return !!(ESR_ELx_ISS2(esr) & ESR_ELx_HDBSSF);
+}
+
 static inline unsigned long esr_brk_comment(unsigned long esr)
 {
 	return esr & ESR_ELx_BRK64_ISS_COMMENT_MASK;
diff --git a/arch/arm64/include/asm/kvm_dirty_bit.h b/arch/arm64/include/asm/kvm_dirty_bit.h
index d828e6b43fe9..eb2039820777 100644
--- a/arch/arm64/include/asm/kvm_dirty_bit.h
+++ b/arch/arm64/include/asm/kvm_dirty_bit.h
@@ -39,5 +39,6 @@ static inline bool vcpu_hdbss_enabled(struct kvm_vcpu *vcpu)
 int kvm_arm_vcpu_alloc_hdbss(struct kvm_vcpu *vcpu);
 void kvm_arm_vcpu_free_hdbss(struct kvm_vcpu *vcpu);
 void kvm_flush_hdbss_buffer(struct kvm_vcpu *vcpu);
+int kvm_handle_hdbss_fault(struct kvm_vcpu *vcpu);

 #endif /* __ARM64_KVM_DIRTY_BIT_H__ */
diff --git a/arch/arm64/kvm/dirty_bit.c b/arch/arm64/kvm/dirty_bit.c
index be0d12555c84..893a8c4248bc 100644
--- a/arch/arm64/kvm/dirty_bit.c
+++ b/arch/arm64/kvm/dirty_bit.c
@@ -98,3 +98,32 @@ void kvm_flush_hdbss_buffer(struct kvm_vcpu *vcpu)
 	vcpu->arch.hdbss.hdbssprod_el2 = prod;
 	isb();
 }
+
+int kvm_handle_hdbss_fault(struct kvm_vcpu *vcpu)
+{
+	u64 prod;
+	u64 fsc;
+
+	if (WARN_ON_ONCE(!system_supports_hdbss()))
+		return -EFAULT;
+
+	if (WARN_ON_ONCE(!vcpu_hdbss_enabled(vcpu)))
+		return -EFAULT;
+
+	prod = read_sysreg_s(SYS_HDBSSPROD_EL2);
+	fsc = FIELD_GET(HDBSSPROD_EL2_FSC_MASK, prod);
+
+	if (fsc == HDBSSPROD_EL2_FSC_OK)
+		/* Buffer full: the exit path drained it before handle_exit. */
+		return 1;
+
+	if (fsc != HDBSSPROD_EL2_FSC_ExternalAbort &&
+	    fsc != HDBSSPROD_EL2_FSC_GPF)
+		WARN_ONCE(1,
+			  "Unexpected HDBSS fault type, FSC: 0x%llx (prod=0x%llx, vcpu=%d)\n",
+			  fsc, prod, vcpu->vcpu_id);
+
+	/* Clear FSC so hardware dirty state updates can resume. */
+	write_sysreg_s(prod & ~HDBSSPROD_EL2_FSC_MASK, SYS_HDBSSPROD_EL2);
+	return -EFAULT;
+}
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 85a98d2c23a9..7bf82d65041c 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -15,6 +15,7 @@
 #include <asm/pgalloc.h>
 #include <asm/cacheflush.h>
 #include <asm/kvm_arm.h>
+#include <asm/kvm_dirty_bit.h>
 #include <asm/kvm_mmu.h>
 #include <asm/kvm_pgtable.h>
 #include <asm/kvm_pkvm.h>
@@ -2315,6 +2316,9 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)

 	is_iabt = kvm_vcpu_trap_is_iabt(vcpu);

+	if (esr_iss2_is_hdbssf(esr))
+		return kvm_handle_hdbss_fault(vcpu);
+
 	if (esr_fsc_is_translation_fault(esr)) {
 		/* Beyond sanitised PARange (which is the IPA limit) */
 		if (fault_ipa >= BIT_ULL(get_kvm_ipa_limit())) {
--
2.43.0