[RFC v2-fix-v4 1/1] x86: Introduce generic protected guest abstraction

From: Kuppuswamy Sathyanarayanan
Date: Wed Jun 09 2021 - 15:42:04 EST

Add a generic way to check if we run with an encrypted guest,
without requiring x86 specific ifdefs. This can then be used in
non architecture specific code. 

prot_guest_has() is used to check for protected guest feature
flags.

Originally-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
---
Changes since RFC v2-fix-v3:
* Introduced ARCH_HAS_PROTECTED_GUEST and moved arch specific checks to
asm/protected_guest.h

Changes since RFC v2-fix-v2:
* Renamed protected_guest_has() to prot_guest_has().
* Changed flag prefix from VM_ to PR_GUEST_
* Merged Borislav AMD implementation fix.

arch/Kconfig | 3 +++
arch/x86/Kconfig | 2 ++
arch/x86/include/asm/protected_guest.h | 20 ++++++++++++++++++++
arch/x86/include/asm/sev.h | 3 +++
arch/x86/include/asm/tdx.h | 7 +++++++
arch/x86/kernel/sev.c | 15 +++++++++++++++
arch/x86/kernel/tdx.c | 15 +++++++++++++++
arch/x86/mm/mem_encrypt.c | 1 +
include/linux/protected_guest.h | 24 ++++++++++++++++++++++++
9 files changed, 90 insertions(+)
create mode 100644 arch/x86/include/asm/protected_guest.h
create mode 100644 include/linux/protected_guest.h

diff --git a/arch/Kconfig b/arch/Kconfig
index c45b770d3579..3c5bf55ee752 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1011,6 +1011,9 @@ config HAVE_ARCH_NVRAM_OPS
config ISA_BUS_API
def_bool ISA

+config ARCH_HAS_PROTECTED_GUEST
+ bool
+
#
# ABI hall of shame
#
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a99adc683db9..fc51579e54ad 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -883,6 +883,7 @@ config INTEL_TDX_GUEST
select PARAVIRT_XL
select X86_X2APIC
select SECURITY_LOCKDOWN_LSM
+ select ARCH_HAS_PROTECTED_GUEST
help
Provide support for running in a trusted domain on Intel processors
equipped with Trusted Domain eXtenstions. TDX is a new Intel
@@ -1544,6 +1545,7 @@ config AMD_MEM_ENCRYPT
select ARCH_HAS_FORCE_DMA_UNENCRYPTED
select INSTRUCTION_DECODER
select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
+ select ARCH_HAS_PROTECTED_GUEST
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/include/asm/protected_guest.h b/arch/x86/include/asm/protected_guest.h
new file mode 100644
index 000000000000..137976ef894a
--- /dev/null
+++ b/arch/x86/include/asm/protected_guest.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (C) 2020 Intel Corporation */
+#ifndef _ASM_PROTECTED_GUEST_H
+#define _ASM_PROTECTED_GUEST_H 1
+
+#include <asm/processor.h>
+#include <asm/tdx.h>
+#include <asm/sev.h>
+
+static inline bool prot_guest_has(unsigned long flag)
+{
+ if (is_tdx_guest())
+ return tdx_protected_guest_has(flag);
+ else if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
+ return sev_protected_guest_has(flag);
+
+ return false;
+}
+
+#endif /* _ASM_PROTECTED_GUEST_H */
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index fa5cd05d3b5b..e9b0b93a3157 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -81,12 +81,15 @@ static __always_inline void sev_es_nmi_complete(void)
__sev_es_nmi_complete();
}
extern int __init sev_es_efi_map_ghcbs(pgd_t *pgd);
+bool sev_protected_guest_has(unsigned long flag);
+
#else
static inline void sev_es_ist_enter(struct pt_regs *regs) { }
static inline void sev_es_ist_exit(void) { }
static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh) { return 0; }
static inline void sev_es_nmi_complete(void) { }
static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }
+static inline bool sev_protected_guest_has(unsigned long flag) { return false; }
#endif

#endif
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index f0c1912837c8..cbfe7479f2a3 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -71,6 +71,8 @@ u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
u64 __tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15,
struct tdx_hypercall_output *out);

+bool tdx_protected_guest_has(unsigned long flag);
+
#else // !CONFIG_INTEL_TDX_GUEST

static inline bool is_tdx_guest(void)
@@ -80,6 +82,11 @@ static inline bool is_tdx_guest(void)

static inline void tdx_early_init(void) { };

+static inline bool tdx_protected_guest_has(unsigned long flag)
+{
+ return false;
+}
+
#endif /* CONFIG_INTEL_TDX_GUEST */

#ifdef CONFIG_INTEL_TDX_GUEST_KVM
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 651b81cd648e..16e5c5f25e6f 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -19,6 +19,7 @@
#include <linux/memblock.h>
#include <linux/kernel.h>
#include <linux/mm.h>
+#include <linux/protected_guest.h>

#include <asm/cpu_entry_area.h>
#include <asm/stacktrace.h>
@@ -1493,3 +1494,17 @@ bool __init handle_vc_boot_ghcb(struct pt_regs *regs)
while (true)
halt();
}
+
+bool sev_protected_guest_has(unsigned long flag)
+{
+ switch (flag) {
+ case PR_GUEST_MEM_ENCRYPT:
+ case PR_GUEST_MEM_ENCRYPT_ACTIVE:
+ case PR_GUEST_UNROLL_STRING_IO:
+ case PR_GUEST_HOST_MEM_ENCRYPT:
+ return true;
+ }
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(sev_protected_guest_has);
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 17725646eb30..111f15c05e24 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -7,6 +7,7 @@
#include <asm/vmx.h>

#include <linux/cpu.h>
+#include <linux/protected_guest.h>

/* TDX Module call Leaf IDs */
#define TDINFO 1
@@ -75,6 +76,20 @@ bool is_tdx_guest(void)
}
EXPORT_SYMBOL_GPL(is_tdx_guest);

+bool tdx_protected_guest_has(unsigned long flag)
+{
+ switch (flag) {
+ case PR_GUEST_MEM_ENCRYPT:
+ case PR_GUEST_MEM_ENCRYPT_ACTIVE:
+ case PR_GUEST_UNROLL_STRING_IO:
+ case PR_GUEST_SHARED_MAPPING_INIT:
+ return true;
+ }
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(tdx_protected_guest_has);
+
static void tdg_get_info(void)
{
u64 ret;
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index ff08dc463634..d0026bce47df 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -20,6 +20,7 @@
#include <linux/bitops.h>
#include <linux/dma-mapping.h>
#include <linux/virtio_config.h>
+#include <linux/protected_guest.h>

#include <asm/tlbflush.h>
#include <asm/fixmap.h>
diff --git a/include/linux/protected_guest.h b/include/linux/protected_guest.h
new file mode 100644
index 000000000000..0facb8547217
--- /dev/null
+++ b/include/linux/protected_guest.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _LINUX_PROTECTED_GUEST_H
+#define _LINUX_PROTECTED_GUEST_H 1
+
+/* Protected Guest Feature Flags (leave 0-0xff for arch specific flags) */
+
+/* Support for guest encryption */
+#define PR_GUEST_MEM_ENCRYPT 0x100
+/* Encryption support is active */
+#define PR_GUEST_MEM_ENCRYPT_ACTIVE 0x101
+/* Support for unrolled string IO */
+#define PR_GUEST_UNROLL_STRING_IO 0x102
+/* Support for host memory encryption */
+#define PR_GUEST_HOST_MEM_ENCRYPT 0x103
+/* Support for shared mapping initialization (after early init) */
+#define PR_GUEST_SHARED_MAPPING_INIT 0x104
+
+#ifdef CONFIG_ARCH_HAS_PROTECTED_GUEST
+#include <asm/protected_guest.h>
+#else
+static inline bool prot_guest_has(unsigned long flag) { return false; }
+#endif
+
+#endif /* _LINUX_PROTECTED_GUEST_H */
--
2.25.1