[RFC PATCH v2 10/26] KVM: arm64: Introduce an early Hyp page allocator

[Quentin Perret <qperret@google.com>]

With nVHE, the host currently creates all s1 hypervisor mappings at EL1
during boot, installs them at EL2, and extends them as required (e.g.
when creating a new VM). But in a world where the host is no longer
trusted, it cannot have full control over the code mapped in the
hypervisor.

In preparation for enabling the hypervisor to create its own s1 mappings
during boot, introduce an early page allocator, with minimal
functionality. This allocator is designed to be used only during early
bootstrap of the hyp code when memory protection is enabled, which will
then switch to using a full-fledged page allocator after init.

Signed-off-by: Quentin Perret <qperret@google.com>
---
 arch/arm64/kvm/hyp/include/nvhe/early_alloc.h | 14 +++++
 arch/arm64/kvm/hyp/include/nvhe/memory.h      | 24 ++++++++
 arch/arm64/kvm/hyp/nvhe/Makefile              |  2 +-
 arch/arm64/kvm/hyp/nvhe/early_alloc.c         | 60 +++++++++++++++++++
 arch/arm64/kvm/hyp/nvhe/psci-relay.c          |  4 +-
 5 files changed, 100 insertions(+), 4 deletions(-)
 create mode 100644 arch/arm64/kvm/hyp/include/nvhe/early_alloc.h
 create mode 100644 arch/arm64/kvm/hyp/include/nvhe/memory.h
 create mode 100644 arch/arm64/kvm/hyp/nvhe/early_alloc.c

diff --git a/arch/arm64/kvm/hyp/include/nvhe/early_alloc.h b/arch/arm64/kvm/hyp/include/nvhe/early_alloc.h
new file mode 100644
index 000000000000..68ce2bf9a718
--- /dev/null
+++ b/arch/arm64/kvm/hyp/include/nvhe/early_alloc.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __KVM_HYP_EARLY_ALLOC_H
+#define __KVM_HYP_EARLY_ALLOC_H
+
+#include <asm/kvm_pgtable.h>
+
+void hyp_early_alloc_init(void *virt, unsigned long size);
+unsigned long hyp_early_alloc_nr_pages(void);
+void *hyp_early_alloc_page(void *arg);
+void *hyp_early_alloc_contig(unsigned int nr_pages);
+
+extern struct kvm_pgtable_mm_ops hyp_early_alloc_mm_ops;
+
+#endif /* __KVM_HYP_EARLY_ALLOC_H */
diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h
new file mode 100644
index 000000000000..64c44c142c95
--- /dev/null
+++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __KVM_HYP_MEMORY_H
+#define __KVM_HYP_MEMORY_H
+
+#include <asm/page.h>
+
+#include <linux/types.h>
+
+extern s64 hyp_physvirt_offset;
+
+#define __hyp_pa(virt)	((phys_addr_t)(virt) + hyp_physvirt_offset)
+#define __hyp_va(virt)	((void *)((phys_addr_t)(virt) - hyp_physvirt_offset))
+
+static inline void *hyp_phys_to_virt(phys_addr_t phys)
+{
+	return __hyp_va(phys);
+}
+
+static inline phys_addr_t hyp_virt_to_phys(void *addr)
+{
+	return __hyp_pa(addr);
+}
+
+#endif /* __KVM_HYP_MEMORY_H */
diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index 590fdefb42dd..1fc0684a7678 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -10,7 +10,7 @@ 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
+	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.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/early_alloc.c b/arch/arm64/kvm/hyp/nvhe/early_alloc.c
new file mode 100644
index 000000000000..de4c45662970
--- /dev/null
+++ b/arch/arm64/kvm/hyp/nvhe/early_alloc.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 Google LLC
+ * Author: Quentin Perret <qperret@google.com>
+ */
+
+#include <asm/kvm_pgtable.h>
+
+#include <nvhe/memory.h>
+
+struct kvm_pgtable_mm_ops hyp_early_alloc_mm_ops;
+s64 __ro_after_init hyp_physvirt_offset;
+
+static unsigned long base;
+static unsigned long end;
+static unsigned long cur;
+
+unsigned long hyp_early_alloc_nr_pages(void)
+{
+	return (cur - base) >> PAGE_SHIFT;
+}
+
+extern void clear_page(void *to);
+
+void *hyp_early_alloc_contig(unsigned int nr_pages)
+{
+	unsigned long ret = cur, i, p;
+
+	if (!nr_pages)
+		return NULL;
+
+	cur += nr_pages << PAGE_SHIFT;
+	if (cur > end) {
+		cur = ret;
+		return NULL;
+	}
+
+	for (i = 0; i < nr_pages; i++) {
+		p = ret + (i << PAGE_SHIFT);
+		clear_page((void *)(p));
+	}
+
+	return (void *)ret;
+}
+
+void *hyp_early_alloc_page(void *arg)
+{
+	return hyp_early_alloc_contig(1);
+}
+
+void hyp_early_alloc_init(unsigned long virt, unsigned long size)
+{
+	base = virt;
+	end = virt + size;
+	cur = virt;
+
+	hyp_early_alloc_mm_ops.zalloc_page = hyp_early_alloc_page;
+	hyp_early_alloc_mm_ops.phys_to_virt = hyp_phys_to_virt;
+	hyp_early_alloc_mm_ops.virt_to_phys = hyp_virt_to_phys;
+}
diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
index e3947846ffcb..bdd8054bce4c 100644
--- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
+++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
@@ -11,6 +11,7 @@
 #include <linux/kvm_host.h>
 #include <uapi/linux/psci.h>
 
+#include <nvhe/memory.h>
 #include <nvhe/trap_handler.h>
 
 void kvm_hyp_cpu_entry(unsigned long r0);
@@ -20,9 +21,6 @@ void __noreturn __host_enter(struct kvm_cpu_context *host_ctxt);
 
 /* Config options set by the host. */
 struct kvm_host_psci_config __ro_after_init kvm_host_psci_config;
-s64 __ro_after_init hyp_physvirt_offset;
-
-#define __hyp_pa(x) ((phys_addr_t)((x)) + hyp_physvirt_offset)
 
 #define INVALID_CPU_ID	UINT_MAX
 
-- 
2.30.0.284.gd98b1dd5eaa7-goog