[PATCH v2 09/14] arm64: Enable memory encrypt for Realms

From: Steven Price <steven.price@arm.com>
To: kvm@vger.kernel.org, kvmarm@lists.linux.dev
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
	James Morse <james.morse@arm.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Zenghui Yu <yuzenghui@huawei.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Joey Gouly <joey.gouly@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Christoffer Dall <christoffer.dall@arm.com>,
	Fuad Tabba <tabba@google.com>,
	linux-coco@lists.linux.dev,
	Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>,
	Steven Price <steven.price@arm.com>
Subject: [PATCH v2 09/14] arm64: Enable memory encrypt for Realms
Date: Fri, 12 Apr 2024 09:42:08 +0100	[thread overview]
Message-ID: <20240412084213.1733764-10-steven.price@arm.com> (raw)
In-Reply-To: <20240412084213.1733764-1-steven.price@arm.com>

From: Suzuki K Poulose <suzuki.poulose@arm.com>

Use the memory encryption APIs to trigger a RSI call to request a
transition between protected memory and shared memory (or vice versa)
and updating the kernel's linear map of modified pages to flip the top
bit of the IPA. This requires that block mappings are not used in the
direct map for realm guests.

Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Co-developed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/Kconfig                   |  3 ++
 arch/arm64/include/asm/mem_encrypt.h | 19 +++++++++++
 arch/arm64/kernel/rsi.c              | 12 +++++++
 arch/arm64/mm/pageattr.c             | 48 ++++++++++++++++++++++++++--
 4 files changed, 79 insertions(+), 3 deletions(-)
 create mode 100644 arch/arm64/include/asm/mem_encrypt.h

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7b11c98b3e84..ffd4685a3029 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -20,6 +20,7 @@ config ARM64
 	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2
 	select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
 	select ARCH_HAS_CACHE_LINE_SIZE
+	select ARCH_HAS_CC_PLATFORM
 	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DEBUG_VIRTUAL
 	select ARCH_HAS_DEBUG_VM_PGTABLE
@@ -40,6 +41,8 @@ config ARM64
 	select ARCH_HAS_SETUP_DMA_OPS
 	select ARCH_HAS_SET_DIRECT_MAP
 	select ARCH_HAS_SET_MEMORY
+	select ARCH_HAS_MEM_ENCRYPT
+	select ARCH_HAS_FORCE_DMA_UNENCRYPTED
 	select ARCH_STACKWALK
 	select ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_HAS_STRICT_MODULE_RWX
diff --git a/arch/arm64/include/asm/mem_encrypt.h b/arch/arm64/include/asm/mem_encrypt.h
new file mode 100644
index 000000000000..7381f9585321
--- /dev/null
+++ b/arch/arm64/include/asm/mem_encrypt.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 ARM Ltd.
+ */
+
+#ifndef __ASM_MEM_ENCRYPT_H
+#define __ASM_MEM_ENCRYPT_H
+
+#include <asm/rsi.h>
+
+/* All DMA must be to non-secure memory for now */
+static inline bool force_dma_unencrypted(struct device *dev)
+{
+	return is_realm_world();
+}
+
+int set_memory_encrypted(unsigned long addr, int numpages);
+int set_memory_decrypted(unsigned long addr, int numpages);
+#endif
diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
index 5c8ed3aaa35f..ba3f346e7a91 100644
--- a/arch/arm64/kernel/rsi.c
+++ b/arch/arm64/kernel/rsi.c
@@ -6,6 +6,7 @@
 #include <linux/jump_label.h>
 #include <linux/memblock.h>
 #include <linux/swiotlb.h>
+#include <linux/cc_platform.h>
 
 #include <asm/rsi.h>
 
@@ -19,6 +20,17 @@ unsigned int phys_mask_shift = CONFIG_ARM64_PA_BITS;
 DEFINE_STATIC_KEY_FALSE_RO(rsi_present);
 EXPORT_SYMBOL(rsi_present);
 
+bool cc_platform_has(enum cc_attr attr)
+{
+	switch (attr) {
+	case CC_ATTR_MEM_ENCRYPT:
+		return is_realm_world();
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL_GPL(cc_platform_has);
+
 static bool rsi_version_matches(void)
 {
 	unsigned long ver;
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 0c4e3ecf989d..229b6d9990f5 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -5,10 +5,12 @@
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/module.h>
+#include <linux/mem_encrypt.h>
 #include <linux/sched.h>
 #include <linux/vmalloc.h>
 
 #include <asm/cacheflush.h>
+#include <asm/pgtable-prot.h>
 #include <asm/set_memory.h>
 #include <asm/tlbflush.h>
 #include <asm/kfence.h>
@@ -23,14 +25,16 @@ bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED
 bool can_set_direct_map(void)
 {
 	/*
-	 * rodata_full and DEBUG_PAGEALLOC require linear map to be
-	 * mapped at page granularity, so that it is possible to
+	 * rodata_full, DEBUG_PAGEALLOC and a Realm guest all require linear
+	 * map to be mapped at page granularity, so that it is possible to
 	 * protect/unprotect single pages.
 	 *
 	 * KFENCE pool requires page-granular mapping if initialized late.
+	 *
+	 * Realms need to make pages shared/protected at page granularity.
 	 */
 	return rodata_full || debug_pagealloc_enabled() ||
-	       arm64_kfence_can_set_direct_map();
+		arm64_kfence_can_set_direct_map() || is_realm_world();
 }
 
 static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
@@ -41,6 +45,7 @@ static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
 	pte = clear_pte_bit(pte, cdata->clear_mask);
 	pte = set_pte_bit(pte, cdata->set_mask);
 
+	/* TODO: Break before make for PROT_NS_SHARED updates */
 	__set_pte(ptep, pte);
 	return 0;
 }
@@ -192,6 +197,43 @@ int set_direct_map_default_noflush(struct page *page)
 				   PAGE_SIZE, change_page_range, &data);
 }
 
+static int __set_memory_encrypted(unsigned long addr,
+				  int numpages,
+				  bool encrypt)
+{
+	unsigned long set_prot = 0, clear_prot = 0;
+	phys_addr_t start, end;
+
+	if (!is_realm_world())
+		return 0;
+
+	WARN_ON(!__is_lm_address(addr));
+	start = __virt_to_phys(addr);
+	end = start + numpages * PAGE_SIZE;
+
+	if (encrypt) {
+		clear_prot = PROT_NS_SHARED;
+		set_memory_range_protected(start, end);
+	} else {
+		set_prot = PROT_NS_SHARED;
+		set_memory_range_shared(start, end);
+	}
+
+	return __change_memory_common(addr, PAGE_SIZE * numpages,
+				      __pgprot(set_prot),
+				      __pgprot(clear_prot));
+}
+
+int set_memory_encrypted(unsigned long addr, int numpages)
+{
+	return __set_memory_encrypted(addr, numpages, true);
+}
+
+int set_memory_decrypted(unsigned long addr, int numpages)
+{
+	return __set_memory_encrypted(addr, numpages, false);
+}
+
 #ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
-- 
2.34.1

