linux-kernel - [PATCH v2 1/7] KVM: LoongArch: selftests: Add system registers save and restore on exception

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Message-Id: <20251104113700.1561752-2-maobibo@loongson.cn>
Date: Tue,  4 Nov 2025 19:36:53 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Paolo Bonzini <pbonzini@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Huacai Chen <chenhuacai@...nel.org>,
	Tianrui Zhao <zhaotianrui@...ngson.cn>,
	Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	loongarch@...ts.linux.dev,
	linux-kselftest@...r.kernel.org
Subject: [PATCH v2 1/7] KVM: LoongArch: selftests: Add system registers save and restore on exception

When system returns from exception with ertn instruction, PC comes
from LOONGARCH_CSR_ERA, and CSR_CRMD comes LOONGARCH_CSR_PRMD.

Here save CSR register CSR_ERA and CSR_PRMD in stack, and restore them
from stack. So it can be modified by exception handler in future.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
 tools/testing/selftests/kvm/include/loongarch/processor.h | 5 ++++-
 tools/testing/selftests/kvm/lib/loongarch/exception.S     | 6 ++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/include/loongarch/processor.h b/tools/testing/selftests/kvm/include/loongarch/processor.h
index 6427a3275e6a..374caddfb0db 100644
--- a/tools/testing/selftests/kvm/include/loongarch/processor.h
+++ b/tools/testing/selftests/kvm/include/loongarch/processor.h
@@ -124,18 +124,21 @@ struct ex_regs {
 	unsigned long pc;
 	unsigned long estat;
 	unsigned long badv;
+	unsigned long prmd;
 };
 
 #define PC_OFFSET_EXREGS		offsetof(struct ex_regs, pc)
 #define ESTAT_OFFSET_EXREGS		offsetof(struct ex_regs, estat)
 #define BADV_OFFSET_EXREGS		offsetof(struct ex_regs, badv)
+#define PRMD_OFFSET_EXREGS		offsetof(struct ex_regs, prmd)
 #define EXREGS_SIZE			sizeof(struct ex_regs)
 
 #else
 #define PC_OFFSET_EXREGS		((EXREGS_GPRS + 0) * 8)
 #define ESTAT_OFFSET_EXREGS		((EXREGS_GPRS + 1) * 8)
 #define BADV_OFFSET_EXREGS		((EXREGS_GPRS + 2) * 8)
-#define EXREGS_SIZE			((EXREGS_GPRS + 3) * 8)
+#define PRMD_OFFSET_EXREGS		((EXREGS_GPRS + 3) * 8)
+#define EXREGS_SIZE			((EXREGS_GPRS + 4) * 8)
 #endif
 
 #endif /* SELFTEST_KVM_PROCESSOR_H */
diff --git a/tools/testing/selftests/kvm/lib/loongarch/exception.S b/tools/testing/selftests/kvm/lib/loongarch/exception.S
index 88bfa505c6f5..3f1e4b67c5ae 100644
--- a/tools/testing/selftests/kvm/lib/loongarch/exception.S
+++ b/tools/testing/selftests/kvm/lib/loongarch/exception.S
@@ -51,9 +51,15 @@ handle_exception:
 	st.d   t0, sp, ESTAT_OFFSET_EXREGS
 	csrrd  t0, LOONGARCH_CSR_BADV
 	st.d   t0, sp, BADV_OFFSET_EXREGS
+	csrrd  t0, LOONGARCH_CSR_PRMD
+	st.d   t0, sp, PRMD_OFFSET_EXREGS
 
 	or     a0, sp, zero
 	bl route_exception
+	ld.d   t0, sp, PC_OFFSET_EXREGS
+	csrwr  t0, LOONGARCH_CSR_ERA
+	ld.d   t0, sp, PRMD_OFFSET_EXREGS
+	csrwr  t0, LOONGARCH_CSR_PRMD
 	restore_gprs sp
 	csrrd  sp, LOONGARCH_CSR_KS0
 	ertn
-- 
2.39.3