[PATCHv2 0/3] Share common features between AMD SEV / TDX guest

[PATCHv2 0/3] Share common features between AMD SEV / TDX guest

[Kirill A. Shutemov]

Hi All,

Intel's Trust Domain Extensions (TDX) protect guest VMs from malicious
hosts and some physical attacks. TDX has a lot of similarities to AMD SEV.
Features like encryption/decryption and string I/O unroll support can
be shared between these two technologies.

This patch set adds infrastructure changes required to share the code
between AMD SEV and TDX.

v2:
 - Squash first two patches
 - Rename print_amd_mem_encrypt_feature_info() to print_mem_encrypt_feature_info().
   It will report TDX feature too.

Kirill A. Shutemov (1):
  x86: Move common memory encryption code to mem_encrypt.c

Kuppuswamy Sathyanarayanan (2):
  x86/sev: Use CC_ATTR attribute to generalize string I/O unroll
  x86/sev: Rename mem_encrypt.c to mem_encrypt_amd.c

 arch/x86/Kconfig              |  10 +-
 arch/x86/include/asm/io.h     |  20 +-
 arch/x86/kernel/cc_platform.c |   4 +
 arch/x86/mm/Makefile          |   7 +-
 arch/x86/mm/mem_encrypt.c     | 441 +---------------------------------
 arch/x86/mm/mem_encrypt_amd.c | 438 +++++++++++++++++++++++++++++++++
 include/linux/cc_platform.h   |  11 +
 7 files changed, 473 insertions(+), 458 deletions(-)
 create mode 100644 arch/x86/mm/mem_encrypt_amd.c

-- 
2.32.0

[PATCHv2 1/3] x86/sev: Use CC_ATTR attribute to generalize string I/O unroll

[Kirill A. Shutemov]

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

INS/OUTS instructions are obsolete and hence many hypervisors do not
support its emulation. To support existing usage, string I/O operations
are unrolled using IN/OUT instructions.

AMD SEV platform implements this support by adding unroll logic in
ins#bwl()/outs#bwl() macros with SEV specific checks. Since TDX VM
guests will also need similar support, use CC_ATTR_GUEST_UNROLL_STRING_IO
and generic cc_platform_has() API to implement it.

String I/O helpers were the last users of sev_key_active() interface and
sev_enable_key static key. Remove them.

Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/io.h     | 20 +++-----------------
 arch/x86/kernel/cc_platform.c |  4 ++++
 arch/x86/mm/mem_encrypt.c     | 10 ----------
 include/linux/cc_platform.h   | 11 +++++++++++
 4 files changed, 18 insertions(+), 27 deletions(-)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 5c6a4af0b911..f6d91ecb8026 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -40,6 +40,7 @@
 
 #include <linux/string.h>
 #include <linux/compiler.h>
+#include <linux/cc_platform.h>
 #include <asm/page.h>
 #include <asm/early_ioremap.h>
 #include <asm/pgtable_types.h>
@@ -256,21 +257,6 @@ static inline void slow_down_io(void)
 
 #endif
 
-#ifdef CONFIG_AMD_MEM_ENCRYPT
-#include <linux/jump_label.h>
-
-extern struct static_key_false sev_enable_key;
-static inline bool sev_key_active(void)
-{
-	return static_branch_unlikely(&sev_enable_key);
-}
-
-#else /* !CONFIG_AMD_MEM_ENCRYPT */
-
-static inline bool sev_key_active(void) { return false; }
-
-#endif /* CONFIG_AMD_MEM_ENCRYPT */
-
 #define BUILDIO(bwl, bw, type)						\
 static inline void out##bwl(unsigned type value, int port)		\
 {									\
@@ -301,7 +287,7 @@ static inline unsigned type in##bwl##_p(int port)			\
 									\
 static inline void outs##bwl(int port, const void *addr, unsigned long count) \
 {									\
-	if (sev_key_active()) {						\
+	if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO)) {		\
 		unsigned type *value = (unsigned type *)addr;		\
 		while (count) {						\
 			out##bwl(*value, port);				\
@@ -317,7 +303,7 @@ static inline void outs##bwl(int port, const void *addr, unsigned long count) \
 									\
 static inline void ins##bwl(int port, void *addr, unsigned long count)	\
 {									\
-	if (sev_key_active()) {						\
+	if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO)) {		\
 		unsigned type *value = (unsigned type *)addr;		\
 		while (count) {						\
 			*value = in##bwl(port);				\
diff --git a/arch/x86/kernel/cc_platform.c b/arch/x86/kernel/cc_platform.c
index 03bb2f343ddb..cc1ffe710dd2 100644
--- a/arch/x86/kernel/cc_platform.c
+++ b/arch/x86/kernel/cc_platform.c
@@ -50,6 +50,10 @@ static bool amd_cc_platform_has(enum cc_attr attr)
 	case CC_ATTR_GUEST_STATE_ENCRYPT:
 		return sev_status & MSR_AMD64_SEV_ES_ENABLED;
 
+	case CC_ATTR_GUEST_UNROLL_STRING_IO:
+		return (sev_status & MSR_AMD64_SEV_ENABLED) &&
+			!(sev_status & MSR_AMD64_SEV_ES_ENABLED);
+
 	default:
 		return false;
 	}
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 35487305d8af..b520021a7e7b 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -43,8 +43,6 @@ u64 sme_me_mask __section(".data") = 0;
 u64 sev_status __section(".data") = 0;
 u64 sev_check_data __section(".data") = 0;
 EXPORT_SYMBOL(sme_me_mask);
-DEFINE_STATIC_KEY_FALSE(sev_enable_key);
-EXPORT_SYMBOL_GPL(sev_enable_key);
 
 /* Buffer used for early in-place encryption by BSP, no locking needed */
 static char sme_early_buffer[PAGE_SIZE] __initdata __aligned(PAGE_SIZE);
@@ -499,14 +497,6 @@ void __init mem_encrypt_init(void)
 	/* Call into SWIOTLB to update the SWIOTLB DMA buffers */
 	swiotlb_update_mem_attributes();
 
-	/*
-	 * With SEV, we need to unroll the rep string I/O instructions,
-	 * but SEV-ES supports them through the #VC handler.
-	 */
-	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) &&
-	    !cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
-		static_branch_enable(&sev_enable_key);
-
 	print_mem_encrypt_feature_info();
 }
 
diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
index a075b70b9a70..f47f0c9edb3b 100644
--- a/include/linux/cc_platform.h
+++ b/include/linux/cc_platform.h
@@ -61,6 +61,17 @@ enum cc_attr {
 	 * Examples include SEV-ES.
 	 */
 	CC_ATTR_GUEST_STATE_ENCRYPT,
+
+	/**
+	 * @CC_ATTR_GUEST_UNROLL_STRING_IO: String I/O is implemented with
+	 *                                  IN/OUT instructions
+	 *
+	 * The platform/OS is running as a guest/virtual machine and uses
+	 * IN/OUT instructions in place of string I/O.
+	 *
+	 * Examples include TDX Guest & SEV.
+	 */
+	CC_ATTR_GUEST_UNROLL_STRING_IO,
 };
 
 #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
-- 
2.32.0

[PATCHv2 2/3] x86/sev: Rename mem_encrypt.c to mem_encrypt_amd.c

[Kirill A. Shutemov]

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Both TDX and AMD SEV/SME implement memory encryption features. But
the bulk of the code in mem_encrypt.c is AMD specific. Rename the
file to mem_encrypt_amd.c. A subsequent patch will extract the
parts that can be shared by both TDX and AMD SEV/SME into a generic
file.

No functional changes.

Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/mm/Makefile                             | 8 ++++----
 arch/x86/mm/{mem_encrypt.c => mem_encrypt_amd.c} | 0
 2 files changed, 4 insertions(+), 4 deletions(-)
 rename arch/x86/mm/{mem_encrypt.c => mem_encrypt_amd.c} (100%)

diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 5864219221ca..c9c480641153 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -1,10 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
 # Kernel does not boot with instrumentation of tlb.c and mem_encrypt*.c
 KCOV_INSTRUMENT_tlb.o			:= n
-KCOV_INSTRUMENT_mem_encrypt.o		:= n
+KCOV_INSTRUMENT_mem_encrypt_amd.o	:= n
 KCOV_INSTRUMENT_mem_encrypt_identity.o	:= n
 
-KASAN_SANITIZE_mem_encrypt.o		:= n
+KASAN_SANITIZE_mem_encrypt_amd.o	:= n
 KASAN_SANITIZE_mem_encrypt_identity.o	:= n
 
 # Disable KCSAN entirely, because otherwise we get warnings that some functions
@@ -12,7 +12,7 @@ KASAN_SANITIZE_mem_encrypt_identity.o	:= n
 KCSAN_SANITIZE := n
 
 ifdef CONFIG_FUNCTION_TRACER
-CFLAGS_REMOVE_mem_encrypt.o		= -pg
+CFLAGS_REMOVE_mem_encrypt_amd.o		= -pg
 CFLAGS_REMOVE_mem_encrypt_identity.o	= -pg
 endif
 
@@ -52,6 +52,6 @@ obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS)	+= pkeys.o
 obj-$(CONFIG_RANDOMIZE_MEMORY)			+= kaslr.o
 obj-$(CONFIG_PAGE_TABLE_ISOLATION)		+= pti.o
 
-obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt.o
+obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_amd.o
 obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_identity.o
 obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_boot.o
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt_amd.c
similarity index 100%
rename from arch/x86/mm/mem_encrypt.c
rename to arch/x86/mm/mem_encrypt_amd.c
-- 
2.32.0

[PATCHv2 3/3] x86: Move common memory encryption code to mem_encrypt.c

[Kirill A. Shutemov]

SEV and TDX both protect guest memory from the host access. They both
use guest physical address bits to communicate to the hardware which
pages receive protection or not. SEV and TDX both assume that all I/O
(real devices and virtio) must be performed to pages *without*
protection.

To add this support, AMD SEV code forces force_dma_unencrypted() to
decrypt DMA pages when DMA pages were allocated for I/O. It also uses
swiotlb_update_mem_attributes() to update decryption bits in SWIOTLB
DMA buffers.

Since TDX also uses a similar memory sharing design, all the above
mentioned changes can be reused. So move force_dma_unencrypted(),
SWIOTLB update code and virtio changes out of mem_encrypt_amd.c to
mem_encrypt.c.

Introduce a new config option X86_MEM_ENCRYPT that can be selected
by platforms which uses x86 memory encryption features (needed in both
AMD SEV and Intel TDX guest platforms).

Since the code is moved from mem_encrypt_amdc.c, inherit the same make
flags.

This is preparation for enabling TDX memory encryption support and it
has no functional changes.

Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/Kconfig              | 10 +++--
 arch/x86/mm/Makefile          |  5 +++
 arch/x86/mm/mem_encrypt.c     | 84 +++++++++++++++++++++++++++++++++++
 arch/x86/mm/mem_encrypt_amd.c | 69 ----------------------------
 4 files changed, 96 insertions(+), 72 deletions(-)
 create mode 100644 arch/x86/mm/mem_encrypt.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 95dd1ee01546..793e9b42ace0 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1523,16 +1523,20 @@ config X86_CPA_STATISTICS
 	  helps to determine the effectiveness of preserving large and huge
 	  page mappings when mapping protections are changed.
 
+config X86_MEM_ENCRYPT
+	select ARCH_HAS_FORCE_DMA_UNENCRYPTED
+	select DYNAMIC_PHYSICAL_MASK
+	select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
+	def_bool n
+
 config AMD_MEM_ENCRYPT
 	bool "AMD Secure Memory Encryption (SME) support"
 	depends on X86_64 && CPU_SUP_AMD
 	select DMA_COHERENT_POOL
-	select DYNAMIC_PHYSICAL_MASK
 	select ARCH_USE_MEMREMAP_PROT
-	select ARCH_HAS_FORCE_DMA_UNENCRYPTED
 	select INSTRUCTION_DECODER
-	select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
 	select ARCH_HAS_CC_PLATFORM
+	select X86_MEM_ENCRYPT
 	help
 	  Say yes to enable support for the encryption of system memory.
 	  This requires an AMD processor that supports Secure Memory
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index c9c480641153..fe3d3061fc11 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -1,9 +1,11 @@
 # SPDX-License-Identifier: GPL-2.0
 # Kernel does not boot with instrumentation of tlb.c and mem_encrypt*.c
 KCOV_INSTRUMENT_tlb.o			:= n
+KCOV_INSTRUMENT_mem_encrypt.o		:= n
 KCOV_INSTRUMENT_mem_encrypt_amd.o	:= n
 KCOV_INSTRUMENT_mem_encrypt_identity.o	:= n
 
+KASAN_SANITIZE_mem_encrypt.o		:= n
 KASAN_SANITIZE_mem_encrypt_amd.o	:= n
 KASAN_SANITIZE_mem_encrypt_identity.o	:= n
 
@@ -12,6 +14,7 @@ KASAN_SANITIZE_mem_encrypt_identity.o	:= n
 KCSAN_SANITIZE := n
 
 ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_mem_encrypt.o		= -pg
 CFLAGS_REMOVE_mem_encrypt_amd.o		= -pg
 CFLAGS_REMOVE_mem_encrypt_identity.o	= -pg
 endif
@@ -52,6 +55,8 @@ obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS)	+= pkeys.o
 obj-$(CONFIG_RANDOMIZE_MEMORY)			+= kaslr.o
 obj-$(CONFIG_PAGE_TABLE_ISOLATION)		+= pti.o
 
+obj-$(CONFIG_X86_MEM_ENCRYPT)	+= mem_encrypt.o
 obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_amd.o
+
 obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_identity.o
 obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_boot.o
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
new file mode 100644
index 000000000000..50d209939c66
--- /dev/null
+++ b/arch/x86/mm/mem_encrypt.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Memory Encryption Support Common Code
+ *
+ * Copyright (C) 2016 Advanced Micro Devices, Inc.
+ *
+ * Author: Tom Lendacky <thomas.lendacky@amd.com>
+ */
+
+#include <linux/dma-direct.h>
+#include <linux/dma-mapping.h>
+#include <linux/swiotlb.h>
+#include <linux/cc_platform.h>
+#include <linux/mem_encrypt.h>
+#include <linux/virtio_config.h>
+
+/* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
+bool force_dma_unencrypted(struct device *dev)
+{
+	/*
+	 * For SEV, all DMA must be to unencrypted addresses.
+	 */
+	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
+		return true;
+
+	/*
+	 * For SME, all DMA must be to unencrypted addresses if the
+	 * device does not support DMA to addresses that include the
+	 * encryption mask.
+	 */
+	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {
+		u64 dma_enc_mask = DMA_BIT_MASK(__ffs64(sme_me_mask));
+		u64 dma_dev_mask = min_not_zero(dev->coherent_dma_mask,
+						dev->bus_dma_limit);
+
+		if (dma_dev_mask <= dma_enc_mask)
+			return true;
+	}
+
+	return false;
+}
+
+static void print_mem_encrypt_feature_info(void)
+{
+	pr_info("AMD Memory Encryption Features active:");
+
+	/* Secure Memory Encryption */
+	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {
+		/*
+		 * SME is mutually exclusive with any of the SEV
+		 * features below.
+		 */
+		pr_cont(" SME\n");
+		return;
+	}
+
+	/* Secure Encrypted Virtualization */
+	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
+		pr_cont(" SEV");
+
+	/* Encrypted Register State */
+	if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
+		pr_cont(" SEV-ES");
+
+	pr_cont("\n");
+}
+
+/* Architecture __weak replacement functions */
+void __init mem_encrypt_init(void)
+{
+	if (!cc_platform_has(CC_ATTR_MEM_ENCRYPT))
+		return;
+
+	/* Call into SWIOTLB to update the SWIOTLB DMA buffers */
+	swiotlb_update_mem_attributes();
+
+	print_mem_encrypt_feature_info();
+}
+
+int arch_has_restricted_virtio_memory_access(void)
+{
+	return cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT);
+}
+EXPORT_SYMBOL_GPL(arch_has_restricted_virtio_memory_access);
diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
index b520021a7e7b..2b2d018ea345 100644
--- a/arch/x86/mm/mem_encrypt_amd.c
+++ b/arch/x86/mm/mem_encrypt_amd.c
@@ -413,32 +413,6 @@ void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages, boo
 	notify_range_enc_status_changed(vaddr, npages, enc);
 }
 
-/* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
-bool force_dma_unencrypted(struct device *dev)
-{
-	/*
-	 * For SEV, all DMA must be to unencrypted addresses.
-	 */
-	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
-		return true;
-
-	/*
-	 * For SME, all DMA must be to unencrypted addresses if the
-	 * device does not support DMA to addresses that include the
-	 * encryption mask.
-	 */
-	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {
-		u64 dma_enc_mask = DMA_BIT_MASK(__ffs64(sme_me_mask));
-		u64 dma_dev_mask = min_not_zero(dev->coherent_dma_mask,
-						dev->bus_dma_limit);
-
-		if (dma_dev_mask <= dma_enc_mask)
-			return true;
-	}
-
-	return false;
-}
-
 void __init mem_encrypt_free_decrypted_mem(void)
 {
 	unsigned long vaddr, vaddr_end, npages;
@@ -462,46 +436,3 @@ void __init mem_encrypt_free_decrypted_mem(void)
 
 	free_init_pages("unused decrypted", vaddr, vaddr_end);
 }
-
-static void print_mem_encrypt_feature_info(void)
-{
-	pr_info("AMD Memory Encryption Features active:");
-
-	/* Secure Memory Encryption */
-	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {
-		/*
-		 * SME is mutually exclusive with any of the SEV
-		 * features below.
-		 */
-		pr_cont(" SME\n");
-		return;
-	}
-
-	/* Secure Encrypted Virtualization */
-	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
-		pr_cont(" SEV");
-
-	/* Encrypted Register State */
-	if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
-		pr_cont(" SEV-ES");
-
-	pr_cont("\n");
-}
-
-/* Architecture __weak replacement functions */
-void __init mem_encrypt_init(void)
-{
-	if (!sme_me_mask)
-		return;
-
-	/* Call into SWIOTLB to update the SWIOTLB DMA buffers */
-	swiotlb_update_mem_attributes();
-
-	print_mem_encrypt_feature_info();
-}
-
-int arch_has_restricted_virtio_memory_access(void)
-{
-	return cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT);
-}
-EXPORT_SYMBOL_GPL(arch_has_restricted_virtio_memory_access);
-- 
2.32.0

Re: [PATCHv2 1/3] x86/sev: Use CC_ATTR attribute to generalize string I/O unroll

[Tom Lendacky]

On 12/3/21 7:23 AM, Kirill A. Shutemov wrote:
> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> 
> INS/OUTS instructions are obsolete and hence many hypervisors do not
> support its emulation. To support existing usage, string I/O operations
> are unrolled using IN/OUT instructions.

So this statement is a bit confusing.

The reason they are unrolled for SEV is because, as is stated, the 
hypervisor has to emulate the operation. Since the string is in guest 
private memory, the hypervisor will read encrypted memory and so is unable 
to perform this operation successfully. This is probably the same reason 
the unrolling will be needed for TDX - hypervisor will read all 0xff's, 
correct?

But they won't be unrolled for non-SEV and non-TDX guests. And with 
SEV-ES, the GHCB is used to supply the string in shared memory and so the 
string operations won't be unrolled there, too.

> 
> AMD SEV platform implements this support by adding unroll logic in
> ins#bwl()/outs#bwl() macros with SEV specific checks. Since TDX VM
> guests will also need similar support, use CC_ATTR_GUEST_UNROLL_STRING_IO
> and generic cc_platform_has() API to implement it.

> 
> String I/O helpers were the last users of sev_key_active() interface and
> sev_enable_key static key. Remove them.
> 
> Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
> Reviewed-by: Tony Luck <tony.luck@intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
>   arch/x86/include/asm/io.h     | 20 +++-----------------
>   arch/x86/kernel/cc_platform.c |  4 ++++
>   arch/x86/mm/mem_encrypt.c     | 10 ----------
>   include/linux/cc_platform.h   | 11 +++++++++++
>   4 files changed, 18 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
> index 5c6a4af0b911..f6d91ecb8026 100644
> --- a/arch/x86/include/asm/io.h
> +++ b/arch/x86/include/asm/io.h
> @@ -40,6 +40,7 @@
>   
>   #include <linux/string.h>
>   #include <linux/compiler.h>
> +#include <linux/cc_platform.h>
>   #include <asm/page.h>
>   #include <asm/early_ioremap.h>
>   #include <asm/pgtable_types.h>
> @@ -256,21 +257,6 @@ static inline void slow_down_io(void)
>   
>   #endif
>   
> -#ifdef CONFIG_AMD_MEM_ENCRYPT
> -#include <linux/jump_label.h>
> -
> -extern struct static_key_false sev_enable_key;
> -static inline bool sev_key_active(void)
> -{
> -	return static_branch_unlikely(&sev_enable_key);
> -}
> -
> -#else /* !CONFIG_AMD_MEM_ENCRYPT */
> -
> -static inline bool sev_key_active(void) { return false; }
> -
> -#endif /* CONFIG_AMD_MEM_ENCRYPT */
> -
>   #define BUILDIO(bwl, bw, type)						\
>   static inline void out##bwl(unsigned type value, int port)		\
>   {									\
> @@ -301,7 +287,7 @@ static inline unsigned type in##bwl##_p(int port)			\
>   									\
>   static inline void outs##bwl(int port, const void *addr, unsigned long count) \
>   {									\
> -	if (sev_key_active()) {						\
> +	if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO)) {		\
>   		unsigned type *value = (unsigned type *)addr;		\
>   		while (count) {						\
>   			out##bwl(*value, port);				\
> @@ -317,7 +303,7 @@ static inline void outs##bwl(int port, const void *addr, unsigned long count) \
>   									\
>   static inline void ins##bwl(int port, void *addr, unsigned long count)	\
>   {									\
> -	if (sev_key_active()) {						\
> +	if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO)) {		\
>   		unsigned type *value = (unsigned type *)addr;		\
>   		while (count) {						\
>   			*value = in##bwl(port);				\
> diff --git a/arch/x86/kernel/cc_platform.c b/arch/x86/kernel/cc_platform.c
> index 03bb2f343ddb..cc1ffe710dd2 100644
> --- a/arch/x86/kernel/cc_platform.c
> +++ b/arch/x86/kernel/cc_platform.c
> @@ -50,6 +50,10 @@ static bool amd_cc_platform_has(enum cc_attr attr)
>   	case CC_ATTR_GUEST_STATE_ENCRYPT:
>   		return sev_status & MSR_AMD64_SEV_ES_ENABLED;
>   
> +	case CC_ATTR_GUEST_UNROLL_STRING_IO:
> +		return (sev_status & MSR_AMD64_SEV_ENABLED) &&
> +			!(sev_status & MSR_AMD64_SEV_ES_ENABLED);
> +
>   	default:
>   		return false;
>   	}
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 35487305d8af..b520021a7e7b 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -43,8 +43,6 @@ u64 sme_me_mask __section(".data") = 0;
>   u64 sev_status __section(".data") = 0;
>   u64 sev_check_data __section(".data") = 0;
>   EXPORT_SYMBOL(sme_me_mask);
> -DEFINE_STATIC_KEY_FALSE(sev_enable_key);
> -EXPORT_SYMBOL_GPL(sev_enable_key);
>   
>   /* Buffer used for early in-place encryption by BSP, no locking needed */
>   static char sme_early_buffer[PAGE_SIZE] __initdata __aligned(PAGE_SIZE);
> @@ -499,14 +497,6 @@ void __init mem_encrypt_init(void)
>   	/* Call into SWIOTLB to update the SWIOTLB DMA buffers */
>   	swiotlb_update_mem_attributes();
>   
> -	/*
> -	 * With SEV, we need to unroll the rep string I/O instructions,
> -	 * but SEV-ES supports them through the #VC handler.
> -	 */

I missed this earlier, but can this comment be included with the newly 
added case statement in cc_platform.c?

Thanks,
Tom

> -	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) &&
> -	    !cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
> -		static_branch_enable(&sev_enable_key);
> -
>   	print_mem_encrypt_feature_info();
>   }
>   
> diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
> index a075b70b9a70..f47f0c9edb3b 100644
> --- a/include/linux/cc_platform.h
> +++ b/include/linux/cc_platform.h
> @@ -61,6 +61,17 @@ enum cc_attr {
>   	 * Examples include SEV-ES.
>   	 */
>   	CC_ATTR_GUEST_STATE_ENCRYPT,
> +
> +	/**
> +	 * @CC_ATTR_GUEST_UNROLL_STRING_IO: String I/O is implemented with
> +	 *                                  IN/OUT instructions
> +	 *
> +	 * The platform/OS is running as a guest/virtual machine and uses
> +	 * IN/OUT instructions in place of string I/O.
> +	 *
> +	 * Examples include TDX Guest & SEV.
> +	 */
> +	CC_ATTR_GUEST_UNROLL_STRING_IO,
>   };
>   
>   #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
> 

Re: [PATCHv2 0/3] Share common features between AMD SEV / TDX guest

[Tom Lendacky]

On 12/3/21 7:23 AM, Kirill A. Shutemov wrote:
> Hi All,
> 
> Intel's Trust Domain Extensions (TDX) protect guest VMs from malicious
> hosts and some physical attacks. TDX has a lot of similarities to AMD SEV.
> Features like encryption/decryption and string I/O unroll support can
> be shared between these two technologies.
> 
> This patch set adds infrastructure changes required to share the code
> between AMD SEV and TDX.

For the series:

Tested-by: Tom Lendacky <thomas.lendacky@amd.com>

> 
> v2:
>   - Squash first two patches
>   - Rename print_amd_mem_encrypt_feature_info() to print_mem_encrypt_feature_info().
>     It will report TDX feature too.
> 
> Kirill A. Shutemov (1):
>    x86: Move common memory encryption code to mem_encrypt.c
> 
> Kuppuswamy Sathyanarayanan (2):
>    x86/sev: Use CC_ATTR attribute to generalize string I/O unroll
>    x86/sev: Rename mem_encrypt.c to mem_encrypt_amd.c
> 
>   arch/x86/Kconfig              |  10 +-
>   arch/x86/include/asm/io.h     |  20 +-
>   arch/x86/kernel/cc_platform.c |   4 +
>   arch/x86/mm/Makefile          |   7 +-
>   arch/x86/mm/mem_encrypt.c     | 441 +---------------------------------
>   arch/x86/mm/mem_encrypt_amd.c | 438 +++++++++++++++++++++++++++++++++
>   include/linux/cc_platform.h   |  11 +
>   7 files changed, 473 insertions(+), 458 deletions(-)
>   create mode 100644 arch/x86/mm/mem_encrypt_amd.c
>