[PATCH 14/62] x86/boot/compressed/64: Add stage1 #VC handler
From: Joerg Roedel
Date: Tue Feb 11 2020 - 08:58:35 EST
From: Joerg Roedel <jroedel@xxxxxxx>
Add the first handler for #VC exceptions. At stage 1 there is no GHCB
yet becaue we might still be on the EFI page table and thus can't map
memory unencrypted.
The stage 1 handler is limited to the MSR based protocol to talk to
the hypervisor and can only support CPUID exit-codes, but that is
enough to get to stage 2.
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
---
arch/x86/boot/compressed/Makefile | 1 +
arch/x86/boot/compressed/idt_64.c | 4 ++
arch/x86/boot/compressed/idt_handlers_64.S | 4 ++
arch/x86/boot/compressed/misc.h | 1 +
arch/x86/boot/compressed/sev-es.c | 42 ++++++++++++++
arch/x86/include/asm/msr-index.h | 1 +
arch/x86/include/asm/sev-es.h | 45 +++++++++++++++
arch/x86/include/asm/trap_defs.h | 1 +
arch/x86/kernel/sev-es-shared.c | 66 ++++++++++++++++++++++
9 files changed, 165 insertions(+)
create mode 100644 arch/x86/boot/compressed/sev-es.c
create mode 100644 arch/x86/include/asm/sev-es.h
create mode 100644 arch/x86/kernel/sev-es-shared.c
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index e6b3e0fc48de..583678c78e1b 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -84,6 +84,7 @@ ifdef CONFIG_X86_64
vmlinux-objs-y += $(obj)/idt_64.o $(obj)/idt_handlers_64.o
vmlinux-objs-y += $(obj)/mem_encrypt.o
vmlinux-objs-y += $(obj)/pgtable_64.o
+ vmlinux-objs-$(CONFIG_AMD_MEM_ENCRYPT) += $(obj)/sev-es.o
endif
vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
diff --git a/arch/x86/boot/compressed/idt_64.c b/arch/x86/boot/compressed/idt_64.c
index 84ba57d9d436..bdd20dfd1fd0 100644
--- a/arch/x86/boot/compressed/idt_64.c
+++ b/arch/x86/boot/compressed/idt_64.c
@@ -31,6 +31,10 @@ void load_stage1_idt(void)
{
boot_idt_desc.address = (unsigned long)boot_idt;
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+ set_idt_entry(X86_TRAP_VC, boot_stage1_vc_handler);
+#endif
+
load_boot_idt(&boot_idt_desc);
}
diff --git a/arch/x86/boot/compressed/idt_handlers_64.S b/arch/x86/boot/compressed/idt_handlers_64.S
index f7f1ea66dcbf..330eb4e5c8b3 100644
--- a/arch/x86/boot/compressed/idt_handlers_64.S
+++ b/arch/x86/boot/compressed/idt_handlers_64.S
@@ -71,3 +71,7 @@ SYM_FUNC_END(\name)
.code64
EXCEPTION_HANDLER boot_pf_handler do_boot_page_fault error_code=1
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+EXCEPTION_HANDLER boot_stage1_vc_handler no_ghcb_vc_handler error_code=1
+#endif
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 4e5bc688f467..0e3508c5c15c 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -141,5 +141,6 @@ extern struct desc_ptr boot_idt_desc;
/* IDT Entry Points */
void boot_pf_handler(void);
+void boot_stage1_vc_handler(void);
#endif /* BOOT_COMPRESSED_MISC_H */
diff --git a/arch/x86/boot/compressed/sev-es.c b/arch/x86/boot/compressed/sev-es.c
new file mode 100644
index 000000000000..8d13121a8cf2
--- /dev/null
+++ b/arch/x86/boot/compressed/sev-es.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * AMD Encrypted Register State Support
+ *
+ * Author: Joerg Roedel <jroedel@xxxxxxx>
+ */
+
+#include <linux/kernel.h>
+
+#include <asm/sev-es.h>
+#include <asm/msr-index.h>
+#include <asm/ptrace.h>
+#include <asm/svm.h>
+
+#include "misc.h"
+
+static inline u64 read_ghcb_msr(void)
+{
+ unsigned long low, high;
+
+ asm volatile("rdmsr\n" : "=a" (low), "=d" (high) :
+ "c" (MSR_AMD64_SEV_ES_GHCB));
+
+ return ((high << 32) | low);
+}
+
+static inline void write_ghcb_msr(u64 val)
+{
+ u32 low, high;
+
+ low = val & 0xffffffffUL;
+ high = val >> 32;
+
+ asm volatile("wrmsr\n" : : "c" (MSR_AMD64_SEV_ES_GHCB),
+ "a"(low), "d" (high) : "memory");
+}
+
+#undef __init
+#define __init
+
+/* Include code for early handlers */
+#include "../../kernel/sev-es-shared.c"
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index ebe1685e92dd..b6139b70db54 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -432,6 +432,7 @@
#define MSR_AMD64_IBSBRTARGET 0xc001103b
#define MSR_AMD64_IBSOPDATA4 0xc001103d
#define MSR_AMD64_IBS_REG_COUNT_MAX 8 /* includes MSR_AMD64_IBSBRTARGET */
+#define MSR_AMD64_SEV_ES_GHCB 0xc0010130
#define MSR_AMD64_SEV 0xc0010131
#define MSR_AMD64_SEV_ENABLED_BIT 0
#define MSR_AMD64_SEV_ENABLED BIT_ULL(MSR_AMD64_SEV_ENABLED_BIT)
diff --git a/arch/x86/include/asm/sev-es.h b/arch/x86/include/asm/sev-es.h
new file mode 100644
index 000000000000..f524b40aef07
--- /dev/null
+++ b/arch/x86/include/asm/sev-es.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * AMD Encrypted Register State Support
+ *
+ * Author: Joerg Roedel <jroedel@xxxxxxx>
+ */
+
+#ifndef __ASM_ENCRYPTED_STATE_H
+#define __ASM_ENCRYPTED_STATE_H
+
+#include <linux/types.h>
+
+#define GHCB_SEV_CPUID_REQ 0x004UL
+#define GHCB_CPUID_REQ_EAX 0
+#define GHCB_CPUID_REQ_EBX 1
+#define GHCB_CPUID_REQ_ECX 2
+#define GHCB_CPUID_REQ_EDX 3
+#define GHCB_CPUID_REQ(fn, reg) (GHCB_SEV_CPUID_REQ | \
+ (((unsigned long)reg & 3) << 30) | \
+ (((unsigned long)fn) << 32))
+
+#define GHCB_SEV_CPUID_RESP 0x005UL
+#define GHCB_SEV_TERMINATE 0x100UL
+
+#define GHCB_SEV_GHCB_RESP_CODE(v) ((v) & 0xfff)
+#define VMGEXIT() { asm volatile("rep; vmmcall\n\r"); }
+
+static inline u64 lower_bits(u64 val, unsigned int bits)
+{
+ u64 mask = (1ULL << bits) - 1;
+
+ return (val & mask);
+}
+
+static inline u64 copy_lower_bits(u64 out, u64 in, unsigned int bits)
+{
+ u64 mask = (1ULL << bits) - 1;
+
+ out &= ~mask;
+ out |= lower_bits(in, bits);
+
+ return out;
+}
+
+#endif
diff --git a/arch/x86/include/asm/trap_defs.h b/arch/x86/include/asm/trap_defs.h
index 488f82ac36da..af45d65f0458 100644
--- a/arch/x86/include/asm/trap_defs.h
+++ b/arch/x86/include/asm/trap_defs.h
@@ -24,6 +24,7 @@ enum {
X86_TRAP_AC, /* 17, Alignment Check */
X86_TRAP_MC, /* 18, Machine Check */
X86_TRAP_XF, /* 19, SIMD Floating-Point Exception */
+ X86_TRAP_VC = 29, /* 29, VMM Communication Exception */
X86_TRAP_IRET = 32, /* 32, IRET Exception */
};
diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c
new file mode 100644
index 000000000000..7edf2dfac71f
--- /dev/null
+++ b/arch/x86/kernel/sev-es-shared.c
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * AMD Encrypted Register State Support
+ *
+ * Author: Joerg Roedel <jroedel@xxxxxxx>
+ *
+ * This file is not compiled stand-alone. It contains code shared
+ * between the pre-decompression boot code and the running Linux kernel
+ * and is included directly into both code-bases.
+ */
+
+/*
+ * Boot VC Handler - This is the first VC handler during boot, there is no GHCB
+ * page yet, so it only supports the MSR based communication with the
+ * hypervisor and only the CPUID exit-code.
+ */
+void __init no_ghcb_vc_handler(struct pt_regs *regs)
+{
+ unsigned int fn = lower_bits(regs->ax, 32);
+ unsigned long exit_code = regs->orig_ax;
+ unsigned long val;
+
+ /* Only CPUID is supported via MSR protocol */
+ if (exit_code != SVM_EXIT_CPUID)
+ goto fail;
+
+ write_ghcb_msr(GHCB_CPUID_REQ(fn, GHCB_CPUID_REQ_EAX));
+ VMGEXIT();
+ val = read_ghcb_msr();
+ if (GHCB_SEV_GHCB_RESP_CODE(val) != GHCB_SEV_CPUID_RESP)
+ goto fail;
+ regs->ax = copy_lower_bits(regs->ax, val >> 32, 32);
+
+ write_ghcb_msr(GHCB_CPUID_REQ(fn, GHCB_CPUID_REQ_EBX));
+ VMGEXIT();
+ val = read_ghcb_msr();
+ if (GHCB_SEV_GHCB_RESP_CODE(val) != GHCB_SEV_CPUID_RESP)
+ goto fail;
+ regs->bx = copy_lower_bits(regs->bx, val >> 32, 32);
+
+ write_ghcb_msr(GHCB_CPUID_REQ(fn, GHCB_CPUID_REQ_ECX));
+ VMGEXIT();
+ val = read_ghcb_msr();
+ if (GHCB_SEV_GHCB_RESP_CODE(val) != GHCB_SEV_CPUID_RESP)
+ goto fail;
+ regs->cx = copy_lower_bits(regs->cx, val >> 32, 32);
+
+ write_ghcb_msr(GHCB_CPUID_REQ(fn, GHCB_CPUID_REQ_EDX));
+ VMGEXIT();
+ val = read_ghcb_msr();
+ if (GHCB_SEV_GHCB_RESP_CODE(val) != GHCB_SEV_CPUID_RESP)
+ goto fail;
+ regs->dx = copy_lower_bits(regs->dx, val >> 32, 32);
+
+ regs->ip += 2;
+
+ return;
+
+fail:
+ write_ghcb_msr(GHCB_SEV_TERMINATE);
+ VMGEXIT();
+
+ /* Shouldn't get here - if we do halt the machine */
+ while (true)
+ asm volatile("hlt\n");
+}
--
2.17.1