[Xen-devel] [PATCH v7 12/36] x86/mm: Extend early_memremap() support with additional attrs

[Tom Lendacky <thomas.lendacky@xxxxxxx>]

Add early_memremap() support to be able to specify encrypted and
decrypted mappings with and without write-protection. The use of
write-protection is necessary when encrypting data "in place". The
write-protect attribute is considered cacheable for loads, but not
stores. This implies that the hardware will never give the core a
dirty line with this memtype.

Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
 arch/x86/Kconfig                     |    4 +++
 arch/x86/include/asm/fixmap.h        |   13 ++++++++++
 arch/x86/include/asm/pgtable_types.h |    8 ++++++
 arch/x86/mm/ioremap.c                |   44 ++++++++++++++++++++++++++++++++++
 include/asm-generic/early_ioremap.h  |    2 ++
 mm/early_ioremap.c                   |   10 ++++++++
 6 files changed, 81 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cf74791..0b09b88 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1433,6 +1433,10 @@ config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
          If set to N, then the encryption of system memory can be
          activated with the mem_encrypt=on command line option.
 
+config ARCH_USE_MEMREMAP_PROT
+       def_bool y
+       depends on AMD_MEM_ENCRYPT
+
 # Common NUMA Features
 config NUMA
        bool "Numa Memory Allocation and Scheduler Support"
diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
index d9ff226..dcd9fb5 100644
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -164,6 +164,19 @@ static inline void __set_fixmap(enum fixed_addresses idx,
  */
 #define FIXMAP_PAGE_NOCACHE PAGE_KERNEL_IO_NOCACHE
 
+/*
+ * Early memremap routines used for in-place encryption. The mappings created
+ * by these routines are intended to be used as temporary mappings.
+ */
+void __init *early_memremap_encrypted(resource_size_t phys_addr,
+                                     unsigned long size);
+void __init *early_memremap_encrypted_wp(resource_size_t phys_addr,
+                                        unsigned long size);
+void __init *early_memremap_decrypted(resource_size_t phys_addr,
+                                     unsigned long size);
+void __init *early_memremap_decrypted_wp(resource_size_t phys_addr,
+                                        unsigned long size);
+
 #include <asm-generic/fixmap.h>
 
 #define __late_set_fixmap(idx, phys, flags) __set_fixmap(idx, phys, flags)
diff --git a/arch/x86/include/asm/pgtable_types.h 
b/arch/x86/include/asm/pgtable_types.h
index de32ca3..32095af 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -161,6 +161,7 @@ enum page_cache_mode {
 
 #define _PAGE_CACHE_MASK       (_PAGE_PAT | _PAGE_PCD | _PAGE_PWT)
 #define _PAGE_NOCACHE          (cachemode2protval(_PAGE_CACHE_MODE_UC))
+#define _PAGE_CACHE_WP         (cachemode2protval(_PAGE_CACHE_MODE_WP))
 
 #define PAGE_NONE      __pgprot(_PAGE_PROTNONE | _PAGE_ACCESSED)
 #define PAGE_SHARED    __pgprot(_PAGE_PRESENT | _PAGE_RW | _PAGE_USER | \
@@ -189,6 +190,7 @@ enum page_cache_mode {
 #define __PAGE_KERNEL_VVAR             (__PAGE_KERNEL_RO | _PAGE_USER)
 #define __PAGE_KERNEL_LARGE            (__PAGE_KERNEL | _PAGE_PSE)
 #define __PAGE_KERNEL_LARGE_EXEC       (__PAGE_KERNEL_EXEC | _PAGE_PSE)
+#define __PAGE_KERNEL_WP               (__PAGE_KERNEL | _PAGE_CACHE_WP)
 
 #define __PAGE_KERNEL_IO               (__PAGE_KERNEL)
 #define __PAGE_KERNEL_IO_NOCACHE       (__PAGE_KERNEL_NOCACHE)
@@ -202,6 +204,12 @@ enum page_cache_mode {
 #define _KERNPG_TABLE  (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED |    \
                         _PAGE_DIRTY | _PAGE_ENC)
 
+#define __PAGE_KERNEL_ENC      (__PAGE_KERNEL | _PAGE_ENC)
+#define __PAGE_KERNEL_ENC_WP   (__PAGE_KERNEL_WP | _PAGE_ENC)
+
+#define __PAGE_KERNEL_NOENC    (__PAGE_KERNEL)
+#define __PAGE_KERNEL_NOENC_WP (__PAGE_KERNEL_WP)
+
 #define PAGE_KERNEL            __pgprot(__PAGE_KERNEL | _PAGE_ENC)
 #define PAGE_KERNEL_RO         __pgprot(__PAGE_KERNEL_RO | _PAGE_ENC)
 #define PAGE_KERNEL_EXEC       __pgprot(__PAGE_KERNEL_EXEC | _PAGE_ENC)
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index a382ba9..4feda83 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -422,6 +422,50 @@ void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
        iounmap((void __iomem *)((unsigned long)addr & PAGE_MASK));
 }
 
+#ifdef CONFIG_ARCH_USE_MEMREMAP_PROT
+/* Remap memory with encryption */
+void __init *early_memremap_encrypted(resource_size_t phys_addr,
+                                     unsigned long size)
+{
+       return early_memremap_prot(phys_addr, size, __PAGE_KERNEL_ENC);
+}
+
+/*
+ * Remap memory with encryption and write-protected - cannot be called
+ * before pat_init() is called
+ */
+void __init *early_memremap_encrypted_wp(resource_size_t phys_addr,
+                                        unsigned long size)
+{
+       /* Be sure the write-protect PAT entry is set for write-protect */
+       if (__pte2cachemode_tbl[_PAGE_CACHE_MODE_WP] != _PAGE_CACHE_MODE_WP)
+               return NULL;
+
+       return early_memremap_prot(phys_addr, size, __PAGE_KERNEL_ENC_WP);
+}
+
+/* Remap memory without encryption */
+void __init *early_memremap_decrypted(resource_size_t phys_addr,
+                                     unsigned long size)
+{
+       return early_memremap_prot(phys_addr, size, __PAGE_KERNEL_NOENC);
+}
+
+/*
+ * Remap memory without encryption and write-protected - cannot be called
+ * before pat_init() is called
+ */
+void __init *early_memremap_decrypted_wp(resource_size_t phys_addr,
+                                        unsigned long size)
+{
+       /* Be sure the write-protect PAT entry is set for write-protect */
+       if (__pte2cachemode_tbl[_PAGE_CACHE_MODE_WP] != _PAGE_CACHE_MODE_WP)
+               return NULL;
+
+       return early_memremap_prot(phys_addr, size, __PAGE_KERNEL_NOENC_WP);
+}
+#endif /* CONFIG_ARCH_USE_MEMREMAP_PROT */
+
 static pte_t bm_pte[PAGE_SIZE/sizeof(pte_t)] __page_aligned_bss;
 
 static inline pmd_t * __init early_ioremap_pmd(unsigned long addr)
diff --git a/include/asm-generic/early_ioremap.h 
b/include/asm-generic/early_ioremap.h
index 734ad4d..2edef8d 100644
--- a/include/asm-generic/early_ioremap.h
+++ b/include/asm-generic/early_ioremap.h
@@ -13,6 +13,8 @@ extern void *early_memremap(resource_size_t phys_addr,
                            unsigned long size);
 extern void *early_memremap_ro(resource_size_t phys_addr,
                               unsigned long size);
+extern void *early_memremap_prot(resource_size_t phys_addr,
+                                unsigned long size, unsigned long prot_val);
 extern void early_iounmap(void __iomem *addr, unsigned long size);
 extern void early_memunmap(void *addr, unsigned long size);
 
diff --git a/mm/early_ioremap.c b/mm/early_ioremap.c
index 6d5717b..d7d30da 100644
--- a/mm/early_ioremap.c
+++ b/mm/early_ioremap.c
@@ -226,6 +226,16 @@ void __init early_iounmap(void __iomem *addr, unsigned 
long size)
 }
 #endif
 
+#ifdef CONFIG_ARCH_USE_MEMREMAP_PROT
+void __init *
+early_memremap_prot(resource_size_t phys_addr, unsigned long size,
+                   unsigned long prot_val)
+{
+       return (__force void *)__early_ioremap(phys_addr, size,
+                                              __pgprot(prot_val));
+}
+#endif
+
 #define MAX_MAP_CHUNK  (NR_FIX_BTMAPS << PAGE_SHIFT)
 
 void __init copy_from_early_mem(void *dest, phys_addr_t src, unsigned long 
size)


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