[RFC PATCH v2 13/26] KVM: arm64: Enable access to sanitized CPU features at EL2

[Quentin Perret]

Introduce the infrastructure in KVM enabling to copy CPU feature
registers into EL2-owned data-structures, to allow reading sanitised
values directly at EL2 in nVHE.

Given that only a subset of these features are being read by the
hypervisor, the ones that need to be copied are to be listed under
<asm/kvm_cpufeature.h> together with the name of the nVHE variable that
will hold the copy.

While at it, introduce the first user of this infrastructure by
implementing __flush_dcache_area at EL2, which needs
arm64_ftr_reg_ctrel0.

Signed-off-by: Quentin Perret <qperret at google.com>
---
 arch/arm64/include/asm/cpufeature.h     |  1 +
 arch/arm64/include/asm/kvm_cpufeature.h | 17 ++++++++++++++
 arch/arm64/kernel/cpufeature.c          | 12 ++++++++++
 arch/arm64/kvm/arm.c                    | 31 +++++++++++++++++++++++++
 arch/arm64/kvm/hyp/nvhe/Makefile        |  3 ++-
 arch/arm64/kvm/hyp/nvhe/cache.S         | 13 +++++++++++
 arch/arm64/kvm/hyp/nvhe/cpufeature.c    |  8 +++++++
 7 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/include/asm/kvm_cpufeature.h
 create mode 100644 arch/arm64/kvm/hyp/nvhe/cache.S
 create mode 100644 arch/arm64/kvm/hyp/nvhe/cpufeature.c

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 16063c813dcd..742e9bcc051b 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -600,6 +600,7 @@ void __init setup_cpu_features(void);
 void check_local_cpu_capabilities(void);
 
 u64 read_sanitised_ftr_reg(u32 id);
+int copy_ftr_reg(u32 id, struct arm64_ftr_reg *dst);
 
 static inline bool cpu_supports_mixed_endian_el0(void)
 {
diff --git a/arch/arm64/include/asm/kvm_cpufeature.h b/arch/arm64/include/asm/kvm_cpufeature.h
new file mode 100644
index 000000000000..d34f85cba358
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_cpufeature.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 - Google LLC
+ * Author: Quentin Perret <qperret at google.com>
+ */
+
+#include <asm/cpufeature.h>
+
+#ifndef KVM_HYP_CPU_FTR_REG
+#if defined(__KVM_NVHE_HYPERVISOR__)
+#define KVM_HYP_CPU_FTR_REG(id, name) extern struct arm64_ftr_reg name;
+#else
+#define KVM_HYP_CPU_FTR_REG(id, name) DECLARE_KVM_NVHE_SYM(name);
+#endif
+#endif
+
+KVM_HYP_CPU_FTR_REG(SYS_CTR_EL0, arm64_ftr_reg_ctrel0)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index bc3549663957..c2019aaaadc3 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1113,6 +1113,18 @@ u64 read_sanitised_ftr_reg(u32 id)
 }
 EXPORT_SYMBOL_GPL(read_sanitised_ftr_reg);
 
+int copy_ftr_reg(u32 id, struct arm64_ftr_reg *dst)
+{
+	struct arm64_ftr_reg *regp = get_arm64_ftr_reg(id);
+
+	if (!regp)
+		return -EINVAL;
+
+	memcpy(dst, regp, sizeof(*regp));
+
+	return 0;
+}
+
 #define read_sysreg_case(r)	\
 	case r:		return read_sysreg_s(r)
 
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 51b53ca36dc5..9fd769349e9e 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -34,6 +34,7 @@
 #include <asm/virt.h>
 #include <asm/kvm_arm.h>
 #include <asm/kvm_asm.h>
+#include <asm/kvm_cpufeature.h>
 #include <asm/kvm_mmu.h>
 #include <asm/kvm_emulate.h>
 #include <asm/sections.h>
@@ -1697,6 +1698,29 @@ static void teardown_hyp_mode(void)
 	}
 }
 
+#undef KVM_HYP_CPU_FTR_REG
+#define KVM_HYP_CPU_FTR_REG(id, name) \
+	{ .sys_id = id, .dst = (struct arm64_ftr_reg *)&kvm_nvhe_sym(name) },
+static const struct __ftr_reg_copy_entry {
+	u32			sys_id;
+	struct arm64_ftr_reg	*dst;
+} hyp_ftr_regs[] = {
+	#include <asm/kvm_cpufeature.h>
+};
+
+static int copy_cpu_ftr_regs(void)
+{
+	int i, ret;
+
+	for (i = 0; i < ARRAY_SIZE(hyp_ftr_regs); i++) {
+		ret = copy_ftr_reg(hyp_ftr_regs[i].sys_id, hyp_ftr_regs[i].dst);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 /**
  * Inits Hyp-mode on all online CPUs
  */
@@ -1705,6 +1729,13 @@ static int init_hyp_mode(void)
 	int cpu;
 	int err = 0;
 
+	/*
+	 * Copy the required CPU feature register in their EL2 counterpart
+	 */
+	err = copy_cpu_ftr_regs();
+	if (err)
+		return err;
+
 	/*
 	 * Allocate Hyp PGD and setup Hyp identity mapping
 	 */
diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index 9e5eacfec6ec..72cfe53f106f 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -10,7 +10,8 @@ lib-objs := clear_page.o copy_page.o memcpy.o memset.o
 lib-objs := $(addprefix ../../../lib/, $(lib-objs))
 
 obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
-	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o stub.o page_alloc.o
+	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o stub.o page_alloc.o \
+	 cache.o cpufeature.o
 obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
 	 ../fpsimd.o ../hyp-entry.o ../exception.o
 obj-y += $(lib-objs)
diff --git a/arch/arm64/kvm/hyp/nvhe/cache.S b/arch/arm64/kvm/hyp/nvhe/cache.S
new file mode 100644
index 000000000000..36cef6915428
--- /dev/null
+++ b/arch/arm64/kvm/hyp/nvhe/cache.S
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Code copied from arch/arm64/mm/cache.S.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+#include <asm/alternative.h>
+
+SYM_FUNC_START_PI(__flush_dcache_area)
+	dcache_by_line_op civac, sy, x0, x1, x2, x3
+	ret
+SYM_FUNC_END_PI(__flush_dcache_area)
diff --git a/arch/arm64/kvm/hyp/nvhe/cpufeature.c b/arch/arm64/kvm/hyp/nvhe/cpufeature.c
new file mode 100644
index 000000000000..a887508f996f
--- /dev/null
+++ b/arch/arm64/kvm/hyp/nvhe/cpufeature.c
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 - Google LLC
+ * Author: Quentin Perret <qperret at google.com>
+ */
+
+#define KVM_HYP_CPU_FTR_REG(id, name) struct arm64_ftr_reg name;
+#include <asm/kvm_cpufeature.h>
-- 
2.30.0.284.gd98b1dd5eaa7-goog