[PATCH 14/16] arm64: Enroll into KVM's MMIO guard if required

[Marc Zyngier <maz@xxxxxxxxxx>]

Should a guest desire to enroll into the MMIO guard, allow it to
do so with a command-line option.

Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
 .../admin-guide/kernel-parameters.txt         |  3 ++
 arch/arm64/include/asm/hypervisor.h           |  1 +
 arch/arm64/kernel/setup.c                     |  6 +++
 arch/arm64/mm/ioremap.c                       | 38 +++++++++++++++++++
 4 files changed, 48 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bdb22006f713..a398585bed90 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2062,6 +2062,9 @@
 			1 - Bypass the IOMMU for DMA.
 			unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
 
+	ioremap_guard	[ARM64] enable the KVM MMIO guard functionality
+			if available.
+
 	io7=		[HW] IO7 for Marvel-based Alpha systems
 			See comment before marvel_specify_io7 in
 			arch/alpha/kernel/core_marvel.c.
diff --git a/arch/arm64/include/asm/hypervisor.h b/arch/arm64/include/asm/hypervisor.h
index 8e77f411903f..b130c7b82eaa 100644
--- a/arch/arm64/include/asm/hypervisor.h
+++ b/arch/arm64/include/asm/hypervisor.h
@@ -7,5 +7,6 @@
 void kvm_init_hyp_services(void);
 bool kvm_arm_hyp_service_available(u32 func_id);
 void kvm_arm_init_hyp_services(void);
+void kvm_init_ioremap_services(void);
 
 #endif
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index be5f85b0a24d..c325647f675f 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -49,6 +49,7 @@
 #include <asm/tlbflush.h>
 #include <asm/traps.h>
 #include <asm/efi.h>
+#include <asm/hypervisor.h>
 #include <asm/xen/hypervisor.h>
 #include <asm/mmu_context.h>
 
@@ -445,3 +446,8 @@ static int __init register_arm64_panic_block(void)
 	return 0;
 }
 device_initcall(register_arm64_panic_block);
+
+void kvm_arm_init_hyp_services(void)
+{
+	kvm_init_ioremap_services();
+}
diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
index 0801fd92f0e3..d82b63bcc554 100644
--- a/arch/arm64/mm/ioremap.c
+++ b/arch/arm64/mm/ioremap.c
@@ -23,6 +23,44 @@
 
 static DEFINE_STATIC_KEY_FALSE(ioremap_guard_key);
 
+static bool ioremap_guard;
+static int __init ioremap_guard_setup(char *str)
+{
+	ioremap_guard = true;
+
+	return 0;
+}
+early_param("ioremap_guard", ioremap_guard_setup);
+
+void kvm_init_ioremap_services(void)
+{
+	struct arm_smccc_res res;
+
+	if (!ioremap_guard)
+		return;
+
+	/* We need all the functions to be implemented */
+	if (!kvm_arm_hyp_service_available(ARM_SMCCC_KVM_FUNC_MMIO_GUARD_INFO) ||
+	    !kvm_arm_hyp_service_available(ARM_SMCCC_KVM_FUNC_MMIO_GUARD_ENROLL) ||
+	    !kvm_arm_hyp_service_available(ARM_SMCCC_KVM_FUNC_MMIO_GUARD_MAP) ||
+	    !kvm_arm_hyp_service_available(ARM_SMCCC_KVM_FUNC_MMIO_GUARD_UNMAP))
+		return;
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_INFO_FUNC_ID,
+			     &res);
+	if (res.a0 != PAGE_SIZE)
+		return;
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_ENROLL_FUNC_ID,
+			     &res);
+	if (res.a0 == SMCCC_RET_SUCCESS) {
+		static_branch_enable(&ioremap_guard_key);
+		pr_info("Using KVM MMIO guard for ioremap\n");
+	} else {
+		pr_warn("KVM MMIO guard registration failed (%ld)\n", res.a0);
+	}
+}
+
 void ioremap_page_range_hook(unsigned long addr, unsigned long end,
 			     phys_addr_t phys_addr, pgprot_t prot)
 {
-- 
2.30.2