linux-kernel - [PATCH 13/16] arm64: Implement ioremap/iounmap hooks calling into KVM's MMIO guard

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Message-Id: <20210715163159.1480168-14-maz@kernel.org>
Date:   Thu, 15 Jul 2021 17:31:56 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     will@...nel.org, qperret@...gle.com, dbrazdil@...gle.com,
        Srivatsa Vaddagiri <vatsa@...eaurora.org>,
        Shanker R Donthineni <sdonthineni@...dia.com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        kernel-team@...roid.com
Subject: [PATCH 13/16] arm64: Implement ioremap/iounmap hooks calling into KVM's MMIO guard

Implement the previously defined ioremap/iounmap hooks for arm64,
calling into KVM's MMIO guard if available.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 arch/arm64/mm/ioremap.c | 56 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
index b7c81dacabf0..0801fd92f0e3 100644
--- a/arch/arm64/mm/ioremap.c
+++ b/arch/arm64/mm/ioremap.c
@@ -9,13 +9,69 @@
  * Copyright (C) 2012 ARM Ltd.
  */
 
+#define pr_fmt(fmt)	"ioremap: " fmt
+
 #include <linux/export.h>
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
 #include <linux/io.h>
+#include <linux/arm-smccc.h>
 
 #include <asm/fixmap.h>
 #include <asm/tlbflush.h>
+#include <asm/hypervisor.h>
+
+static DEFINE_STATIC_KEY_FALSE(ioremap_guard_key);
+
+void ioremap_page_range_hook(unsigned long addr, unsigned long end,
+			     phys_addr_t phys_addr, pgprot_t prot)
+{
+	size_t size = end - addr;
+
+	if (!static_branch_unlikely(&ioremap_guard_key))
+		return;
+
+	if (pfn_valid(__phys_to_pfn(phys_addr)))
+		return;
+
+	while (size) {
+		struct arm_smccc_res res;
+
+		arm_smccc_1_1_hvc(ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_MAP_FUNC_ID,
+				  phys_addr, prot, &res);
+		if (res.a0 != SMCCC_RET_SUCCESS) {
+			pr_warn_ratelimited("Failed to register %llx\n",
+					    phys_addr);
+			return;
+		}
+
+		size -= PAGE_SIZE;
+		phys_addr += PAGE_SIZE;
+	}
+}
+
+void iounmap_page_range_hook(phys_addr_t phys_addr, size_t size)
+{
+	if (!static_branch_unlikely(&ioremap_guard_key))
+		return;
+
+	VM_BUG_ON(phys_addr & ~PAGE_MASK || size & ~PAGE_MASK);
+
+	while (size) {
+		struct arm_smccc_res res;
+
+		arm_smccc_1_1_hvc(ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_UNMAP_FUNC_ID,
+				  phys_addr, &res);
+		if (res.a0 != SMCCC_RET_SUCCESS) {
+			pr_warn_ratelimited("Failed to unregister %llx\n",
+					    phys_addr);
+			return;
+		}
+
+		size -= PAGE_SIZE;
+		phys_addr += PAGE_SIZE;
+	}
+}
 
 static void __iomem *__ioremap_caller(phys_addr_t phys_addr, size_t size,
 				      pgprot_t prot, void *caller)
-- 
2.30.2