linux-kernel - [PATCH v3 02/12] KVM: arm64: selftests: Add write_sysreg_s and read_sysreg

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Message-Id: <20210901211412.4171835-3-rananta@google.com>
Date:   Wed,  1 Sep 2021 21:14:02 +0000
From:   Raghavendra Rao Ananta <rananta@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Peter Shier <pshier@...gle.com>,
        Ricardo Koller <ricarkol@...gle.com>,
        Oliver Upton <oupton@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Raghavendra Rao Anata <rananta@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH v3 02/12] KVM: arm64: selftests: Add write_sysreg_s and read_sysreg_s

For register names that are unsupported by the assembler or the ones
without architectural names, add the macros write_sysreg_s and
read_sysreg_s to support them.

The functionality is derived from kvm-unit-tests and kernel's
arch/arm64/include/asm/sysreg.h.

Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
---
 .../selftests/kvm/include/aarch64/processor.h | 61 +++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/aarch64/processor.h b/tools/testing/selftests/kvm/include/aarch64/processor.h
index 3cbaf5c1e26b..082cc97ad8d3 100644
--- a/tools/testing/selftests/kvm/include/aarch64/processor.h
+++ b/tools/testing/selftests/kvm/include/aarch64/processor.h
@@ -118,6 +118,67 @@ void vm_install_exception_handler(struct kvm_vm *vm,
 void vm_install_sync_handler(struct kvm_vm *vm,
 		int vector, int ec, handler_fn handler);
 
+/*
+ * ARMv8 ARM reserves the following encoding for system registers:
+ * (Ref: ARMv8 ARM, Section: "System instruction class encoding overview",
+ *  C5.2, version:ARM DDI 0487A.f)
+ *	[20-19] : Op0
+ *	[18-16] : Op1
+ *	[15-12] : CRn
+ *	[11-8]  : CRm
+ *	[7-5]   : Op2
+ */
+#define Op0_shift	19
+#define Op0_mask	0x3
+#define Op1_shift	16
+#define Op1_mask	0x7
+#define CRn_shift	12
+#define CRn_mask	0xf
+#define CRm_shift	8
+#define CRm_mask	0xf
+#define Op2_shift	5
+#define Op2_mask	0x7
+
+/*
+ * When accessed from guests, the ARM64_SYS_REG() doesn't work since it
+ * generates a different encoding for additional KVM processing, and is
+ * only suitable for userspace to access the register via ioctls.
+ * Hence, define a 'pure' sys_reg() here to generate the encodings as per spec.
+ */
+#define sys_reg(op0, op1, crn, crm, op2) \
+	(((op0) << Op0_shift) | ((op1) << Op1_shift) | \
+	 ((crn) << CRn_shift) | ((crm) << CRm_shift) | \
+	 ((op2) << Op2_shift))
+
+asm(
+"	.irp	num,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30\n"
+"	.equ	.L__reg_num_x\\num, \\num\n"
+"	.endr\n"
+"	.equ	.L__reg_num_xzr, 31\n"
+"\n"
+"	.macro	mrs_s, rt, sreg\n"
+"	.inst	0xd5200000|(\\sreg)|(.L__reg_num_\\rt)\n"
+"	.endm\n"
+"\n"
+"	.macro	msr_s, sreg, rt\n"
+"	.inst	0xd5000000|(\\sreg)|(.L__reg_num_\\rt)\n"
+"	.endm\n"
+);
+
+/*
+ * read_sysreg_s() and write_sysreg_s()'s 'reg' has to be encoded via sys_reg()
+ */
+#define read_sysreg_s(reg) ({						\
+	u64 __val;							\
+	asm volatile("mrs_s %0, "__stringify(reg) : "=r" (__val));	\
+	__val;								\
+})
+
+#define write_sysreg_s(reg, val) do {					\
+	u64 __val = (u64)val;						\
+	asm volatile("msr_s "__stringify(reg) ", %x0" : : "rZ" (__val));\
+} while (0)
+
 #define write_sysreg(reg, val)						  \
 ({									  \
 	u64 __val = (u64)(val);						  \
-- 
2.33.0.153.gba50c8fa24-goog