linux-kernel - [RFC PATCH 07/26] kvm: arm64: Support per_cpu

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Message-Id: <20201104183630.27513-8-dbrazdil@google.com>
Date:   Wed,  4 Nov 2020 18:36:11 +0000
From:   David Brazdil <dbrazdil@...gle.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Dennis Zhou <dennis@...nel.org>,
        Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Quentin Perret <qperret@...gle.com>,
        Andrew Scull <ascull@...gle.com>, kernel-team@...roid.com,
        David Brazdil <dbrazdil@...gle.com>
Subject: [RFC PATCH 07/26] kvm: arm64: Support per_cpu_ptr in nVHE hyp code

When compiling with __KVM_NVHE_HYPERVISOR__ redefine per_cpu_offset() to
__hyp_per_cpu_offset() which looks up the base of the nVHE per-CPU
region of the given cpu and computes its offset from the
.hyp.data..percpu section.

This enables use of per_cpu_ptr() helpers in nVHE hyp code. Until now
only this_cpu_ptr() was supported by setting TPIDR_EL2.

Signed-off-by: David Brazdil <dbrazdil@...gle.com>
---
 arch/arm64/include/asm/percpu.h  |  6 ++++++
 arch/arm64/kernel/image-vars.h   |  3 +++
 arch/arm64/kvm/hyp/nvhe/Makefile |  3 ++-
 arch/arm64/kvm/hyp/nvhe/percpu.c | 22 ++++++++++++++++++++++
 4 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/kvm/hyp/nvhe/percpu.c

diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
index 1599e17379d8..8f1661603b78 100644
--- a/arch/arm64/include/asm/percpu.h
+++ b/arch/arm64/include/asm/percpu.h
@@ -239,6 +239,12 @@ PERCPU_RET_OP(add, add, ldadd)
 #define this_cpu_cmpxchg_8(pcp, o, n)	\
 	_pcp_protect_return(cmpxchg_relaxed, pcp, o, n)
 
+#ifdef __KVM_NVHE_HYPERVISOR__
+extern unsigned long __hyp_per_cpu_offset(unsigned int cpu);
+#define __per_cpu_offset
+#define per_cpu_offset(cpu)	__hyp_per_cpu_offset((cpu))
+#endif
+
 #include <asm-generic/percpu.h>
 
 /* Redefine macros for nVHE hyp under DEBUG_PREEMPT to avoid its dependencies. */
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index c615b285ff5b..78a42a7cdb72 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -103,6 +103,9 @@ KVM_NVHE_ALIAS(gic_nonsecure_priorities);
 KVM_NVHE_ALIAS(__start___kvm_ex_table);
 KVM_NVHE_ALIAS(__stop___kvm_ex_table);
 
+/* Array containing bases of nVHE per-CPU memory regions. */
+KVM_NVHE_ALIAS(kvm_arm_hyp_percpu_base);
+
 #endif /* CONFIG_KVM */
 
 #endif /* __ARM64_KERNEL_IMAGE_VARS_H */
diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index ddde15fe85f2..c45f440cce51 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -6,7 +6,8 @@
 asflags-y := -D__KVM_NVHE_HYPERVISOR__
 ccflags-y := -D__KVM_NVHE_HYPERVISOR__
 
-obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o hyp-main.o
+obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
+	 hyp-main.o percpu.o
 obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
 	 ../fpsimd.o ../hyp-entry.o
 
diff --git a/arch/arm64/kvm/hyp/nvhe/percpu.c b/arch/arm64/kvm/hyp/nvhe/percpu.c
new file mode 100644
index 000000000000..5fd0c5696907
--- /dev/null
+++ b/arch/arm64/kvm/hyp/nvhe/percpu.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 - Google LLC
+ * Author: David Brazdil <dbrazdil@...gle.com>
+ */
+
+#include <asm/kvm_asm.h>
+#include <asm/kvm_hyp.h>
+#include <asm/kvm_mmu.h>
+
+unsigned long __hyp_per_cpu_offset(unsigned int cpu)
+{
+	unsigned long *cpu_base_array;
+	unsigned long this_cpu_base;
+
+	if (cpu >= ARRAY_SIZE(kvm_arm_hyp_percpu_base))
+		hyp_panic();
+
+	cpu_base_array = kern_hyp_va(&kvm_arm_hyp_percpu_base[0]);
+	this_cpu_base = kern_hyp_va(cpu_base_array[cpu]);
+	return this_cpu_base - (unsigned long)&__per_cpu_start;
+}
-- 
2.29.1.341.ge80a0c044ae-goog