[RFC v2-fix-v3 1/1] x86: Introduce generic protected guest abstraction

[Kuppuswamy Sathyanarayanan]

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

 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 | 38 +++++++++++++++++++++++++++++++++
 6 files changed, 79 insertions(+)
 create mode 100644 include/linux/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..adfa62e2615e
--- /dev/null
+++ b/include/linux/protected_guest.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _LINUX_PROTECTED_GUEST_H
+#define _LINUX_PROTECTED_GUEST_H 1
+
+#include <asm/processor.h>
+#include <asm/tdx.h>
+#include <asm/sev.h>
+
+/* 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
+
+#if defined(CONFIG_INTEL_TDX_GUEST) || defined(CONFIG_AMD_MEM_ENCRYPT)
+
+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;
+}
+
+#else
+static inline bool prot_guest_has(unsigned long flag) { return false; }
+#endif
+
+#endif /* _LINUX_PROTECTED_GUEST_H */
-- 
2.25.1