From: Joerg Roedel <jroedel@xxxxxxx> Add the infrastructure to handle #VC exceptions when the kernel runs on virtual addresses and has a GHCB mapped. This handler will be used until the runtime #VC handler takes over. Signed-off-by: Joerg Roedel <jroedel@xxxxxxx> Link: https://lore.kernel.org/r/20200724160336.5435-43-joro@xxxxxxxxxx --- arch/x86/include/asm/segment.h | 2 +- arch/x86/include/asm/sev-es.h | 1 + arch/x86/kernel/head64.c | 6 ++ arch/x86/kernel/sev-es-shared.c | 14 ++-- arch/x86/kernel/sev-es.c | 116 ++++++++++++++++++++++++++++++++ arch/x86/mm/extable.c | 1 + 6 files changed, 132 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h index 517920928989..7fdd4facfce7 100644 --- a/arch/x86/include/asm/segment.h +++ b/arch/x86/include/asm/segment.h @@ -226,7 +226,7 @@ #define NUM_EXCEPTION_VECTORS 32 /* Bitmask of exception vectors which push an error code on the stack: */ -#define EXCEPTION_ERRCODE_MASK 0x00027d00 +#define EXCEPTION_ERRCODE_MASK 0x20027d00 #define GDT_SIZE (GDT_ENTRIES*8) #define GDT_ENTRY_TLS_ENTRIES 3 diff --git a/arch/x86/include/asm/sev-es.h b/arch/x86/include/asm/sev-es.h index ec0e112a742b..824e9e6b067c 100644 --- a/arch/x86/include/asm/sev-es.h +++ b/arch/x86/include/asm/sev-es.h @@ -75,5 +75,6 @@ static inline u64 lower_bits(u64 val, unsigned int bits) /* Early IDT entry points for #VC handler */ extern void vc_no_ghcb(void); +extern bool handle_vc_boot_ghcb(struct pt_regs *regs); #endif diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 250fae33bf66..ce2d8284edb9 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -403,6 +403,12 @@ void __init do_early_exception(struct pt_regs *regs, int trapnr) early_make_pgtable(native_read_cr2())) return; +#ifdef CONFIG_AMD_MEM_ENCRYPT + if (trapnr == X86_TRAP_VC && + handle_vc_boot_ghcb(regs)) + return; +#endif + early_fixup_exception(regs, trapnr); } diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c index 18619279a46f..aa77f2eb8d88 100644 --- a/arch/x86/kernel/sev-es-shared.c +++ b/arch/x86/kernel/sev-es-shared.c @@ -9,7 +9,7 @@ * and is included directly into both code-bases. */ -static void __maybe_unused sev_es_terminate(unsigned int reason) +static void sev_es_terminate(unsigned int reason) { u64 val = GHCB_SEV_TERMINATE; @@ -27,7 +27,7 @@ static void __maybe_unused sev_es_terminate(unsigned int reason) asm volatile("hlt\n" : : : "memory"); } -static bool __maybe_unused sev_es_negotiate_protocol(void) +static bool sev_es_negotiate_protocol(void) { u64 val; @@ -46,7 +46,7 @@ static bool __maybe_unused sev_es_negotiate_protocol(void) return true; } -static void __maybe_unused vc_ghcb_invalidate(struct ghcb *ghcb) +static void vc_ghcb_invalidate(struct ghcb *ghcb) { memset(ghcb->save.valid_bitmap, 0, sizeof(ghcb->save.valid_bitmap)); } @@ -58,9 +58,9 @@ static bool vc_decoding_needed(unsigned long exit_code) exit_code <= SVM_EXIT_LAST_EXCP); } -static enum es_result __maybe_unused vc_init_em_ctxt(struct es_em_ctxt *ctxt, - struct pt_regs *regs, - unsigned long exit_code) +static enum es_result vc_init_em_ctxt(struct es_em_ctxt *ctxt, + struct pt_regs *regs, + unsigned long exit_code) { enum es_result ret = ES_OK; @@ -73,7 +73,7 @@ static enum es_result __maybe_unused vc_init_em_ctxt(struct es_em_ctxt *ctxt, return ret; } -static void __maybe_unused vc_finish_insn(struct es_em_ctxt *ctxt) +static void vc_finish_insn(struct es_em_ctxt *ctxt) { ctxt->regs->ip += ctxt->insn.length; } diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c index 0b698b653c0b..bb3e702a71eb 100644 --- a/arch/x86/kernel/sev-es.c +++ b/arch/x86/kernel/sev-es.c @@ -7,7 +7,9 @@ * Author: Joerg Roedel <jroedel@xxxxxxx> */ +#include <linux/sched/debug.h> /* For show_regs() */ #include <linux/kernel.h> +#include <linux/printk.h> #include <linux/mm.h> #include <asm/sev-es.h> @@ -18,6 +20,18 @@ #include <asm/trapnr.h> #include <asm/svm.h> +/* For early boot hypervisor communication in SEV-ES enabled guests */ +static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE); + +/* + * Needs to be in the .data section because we need it NULL before bss is + * cleared + */ +static struct ghcb __initdata *boot_ghcb; + +/* Needed in vc_early_forward_exception */ +void do_early_exception(struct pt_regs *regs, int trapnr); + static inline u64 sev_es_rd_ghcb_msr(void) { return native_read_msr(MSR_AMD64_SEV_ES_GHCB); @@ -161,3 +175,105 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt, /* Include code shared with pre-decompression boot stage */ #include "sev-es-shared.c" + +/* + * This function runs on the first #VC exception after the kernel + * switched to virtual addresses. + */ +static bool __init sev_es_setup_ghcb(void) +{ + /* First make sure the hypervisor talks a supported protocol. */ + if (!sev_es_negotiate_protocol()) + return false; + + /* + * Clear the boot_ghcb. The first exception comes in before the bss + * section is cleared. + */ + memset(&boot_ghcb_page, 0, PAGE_SIZE); + + /* Alright - Make the boot-ghcb public */ + boot_ghcb = &boot_ghcb_page; + + return true; +} + +static void __init vc_early_forward_exception(struct es_em_ctxt *ctxt) +{ + int trapnr = ctxt->fi.vector; + + if (trapnr == X86_TRAP_PF) + native_write_cr2(ctxt->fi.cr2); + + ctxt->regs->orig_ax = ctxt->fi.error_code; + do_early_exception(ctxt->regs, trapnr); +} + +static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt, + struct ghcb *ghcb, + unsigned long exit_code) +{ + enum es_result result; + + switch (exit_code) { + default: + /* + * Unexpected #VC exception + */ + result = ES_UNSUPPORTED; + } + + return result; +} + +bool __init handle_vc_boot_ghcb(struct pt_regs *regs) +{ + unsigned long exit_code = regs->orig_ax; + struct es_em_ctxt ctxt; + enum es_result result; + + /* Do initial setup or terminate the guest */ + if (unlikely(boot_ghcb == NULL && !sev_es_setup_ghcb())) + sev_es_terminate(GHCB_SEV_ES_REASON_GENERAL_REQUEST); + + vc_ghcb_invalidate(boot_ghcb); + + result = vc_init_em_ctxt(&ctxt, regs, exit_code); + if (result == ES_OK) + result = vc_handle_exitcode(&ctxt, boot_ghcb, exit_code); + + /* Done - now check the result */ + switch (result) { + case ES_OK: + vc_finish_insn(&ctxt); + break; + case ES_UNSUPPORTED: + early_printk("PANIC: Unsupported exit-code 0x%02lx in early #VC exception (IP: 0x%lx)\n", + exit_code, regs->ip); + goto fail; + case ES_VMM_ERROR: + early_printk("PANIC: Failure in communication with VMM (exit-code 0x%02lx IP: 0x%lx)\n", + exit_code, regs->ip); + goto fail; + case ES_DECODE_FAILED: + early_printk("PANIC: Failed to decode instruction (exit-code 0x%02lx IP: 0x%lx)\n", + exit_code, regs->ip); + goto fail; + case ES_EXCEPTION: + vc_early_forward_exception(&ctxt); + break; + case ES_RETRY: + /* Nothing to do */ + break; + default: + BUG(); + } + + return true; + +fail: + show_regs(regs); + + while (true) + halt(); +} diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c index 1d6cb07f4f86..3966749d07ac 100644 --- a/arch/x86/mm/extable.c +++ b/arch/x86/mm/extable.c @@ -5,6 +5,7 @@ #include <xen/xen.h> #include <asm/fpu/internal.h> +#include <asm/sev-es.h> #include <asm/traps.h> #include <asm/kdebug.h> -- 2.28.0
