Re: [PATCH 14/62] x86/boot/compressed/64: Add stage1 #VC handler
From: Andy Lutomirski
Date: Tue Feb 11 2020 - 17:23:39 EST
On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro@xxxxxxxxxx> wrote:
>
> 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)
Isn't there a second parameter: unsigned long error_code?
--Andy