[PATCH v3 13/32] KVM: arm64: Enable access to sanitized CPU features at EL2

Quentin Perret
2021-03-03T19:46:21Z

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@google.com>
---
arch/arm64/include/asm/cpufeature.h | 1 +
arch/arm64/include/asm/kvm_cpufeature.h | 17 +++++++++++++++++
arch/arm64/include/asm/kvm_host.h | 4 ++++
arch/arm64/kernel/cpufeature.c | 13 +++++++++++++
arch/arm64/kvm/hyp/nvhe/Makefile | 3 ++-
arch/arm64/kvm/hyp/nvhe/cache.S | 13 +++++++++++++
arch/arm64/kvm/hyp/nvhe/cpufeature.c | 8 ++++++++
arch/arm64/kvm/sys_regs.c | 21 +++++++++++++++++++++
8 files changed, 79 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 61177bac49fa..a85cea2cac57 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -607,6 +607,7 @@ void check_local_cpu_capabilities(void);

u64 read_sanitised_ftr_reg(u32 id);
u64 __read_sysreg_by_encoding(u32 sys_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@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/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 06ca4828005f..459ee557f87c 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -751,9 +751,13 @@ void kvm_clr_pmu_events(u32 clr);

void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu);
void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
+
+void setup_kvm_el2_caps(void);
#else
static inline void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr) {}
static inline void kvm_clr_pmu_events(u32 clr) {}
+
+static inline void setup_kvm_el2_caps(void) {}
#endif

void kvm_vcpu_load_sysregs_vhe(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 066030717a4c..f2d8b479ff74 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1154,6 +1154,18 @@ 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: val = read_sysreg_s(r); break;

@@ -2773,6 +2785,7 @@ void __init setup_cpu_features(void)

setup_system_capabilities();
setup_elf_hwcaps(arm64_elf_hwcaps);
+ setup_kvm_el2_caps();

if (system_supports_32bit_el0())
setup_elf_hwcaps(compat_elf_hwcaps);
diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index 6894a917f290..0033591553fc 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -13,7 +13,8 @@ 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@google.com>
+ */
+
+#define KVM_HYP_CPU_FTR_REG(id, name) struct arm64_ftr_reg name;
+#include <asm/kvm_cpufeature.h>
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 4f2f1e3145de..84be93df52fa 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -21,6 +21,7 @@
#include <asm/debug-monitors.h>
#include <asm/esr.h>
#include <asm/kvm_arm.h>
+#include <asm/kvm_cpufeature.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_hyp.h>
#include <asm/kvm_mmu.h>
@@ -2775,3 +2776,23 @@ void kvm_sys_reg_table_init(void)
/* Clear all higher bits. */
cache_levels &= (1 << (i*3))-1;
}
+
+#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) },
+struct __ftr_reg_copy_entry {
+ u32 sys_id;
+ struct arm64_ftr_reg *dst;
+} hyp_ftr_regs[] __initdata = {
+ #include <asm/kvm_cpufeature.h>
+};
+
+void __init setup_kvm_el2_caps(void)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(hyp_ftr_regs); i++) {
+ WARN(copy_ftr_reg(hyp_ftr_regs[i].sys_id, hyp_ftr_regs[i].dst),
+ "%u feature register not found\n", hyp_ftr_regs[i].sys_id);
+ }
+}