From 95d33bfaa3e169cfec1926e0d0f0c6b0ea75d763 Mon Sep 17 00:00:00 2001 From: Brijesh Singh Date: Wed, 9 Feb 2022 12:10:11 -0600 Subject: [PATCH] x86/sev: Register GHCB memory when SEV-SNP is active The SEV-SNP guest is required by the GHCB spec to register the GHCB's Guest Physical Address (GPA). This is because the hypervisor may prefer that a guest uses a consistent and/or specific GPA for the GHCB associated with a vCPU. For more information, see the GHCB specification section "GHCB GPA Registration". [ bp: Cleanup comments. ] Signed-off-by: Brijesh Singh Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220307213356.2797205-18-brijesh.singh@amd.com --- arch/x86/include/asm/sev.h | 2 ++ arch/x86/kernel/cpu/common.c | 4 ++++ arch/x86/kernel/head64.c | 4 +++- arch/x86/kernel/sev-shared.c | 2 +- arch/x86/kernel/sev.c | 46 ++++++++++++++++++++++++++---------- 5 files changed, 44 insertions(+), 14 deletions(-) diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index e37451849165..48df02713ee0 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -122,6 +122,7 @@ static inline int pvalidate(unsigned long vaddr, bool rmp_psize, bool validate) return rc; } +void setup_ghcb(void); #else static inline void sev_es_ist_enter(struct pt_regs *regs) { } static inline void sev_es_ist_exit(void) { } @@ -130,6 +131,7 @@ static inline void sev_es_nmi_complete(void) { } static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; } static inline int pvalidate(unsigned long vaddr, bool rmp_psize, bool validate) { return 0; } static inline int rmpadjust(unsigned long vaddr, bool rmp_psize, unsigned long attrs) { return 0; } +static inline void setup_ghcb(void) { } #endif #endif diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index ed4417500700..9e4552133872 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -60,6 +60,7 @@ #include #include #include +#include #include "cpu.h" @@ -2124,6 +2125,9 @@ void cpu_init_exception_handling(void) load_TR_desc(); + /* GHCB needs to be setup to handle #VC. */ + setup_ghcb(); + /* Finally load the IDT */ load_current_idt(); } diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index cbc285ddc4ac..83514b9827e6 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -597,8 +597,10 @@ static void startup_64_load_idt(unsigned long physbase) void early_setup_idt(void) { /* VMM Communication Exception */ - if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) + if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) { + setup_ghcb(); set_bringup_idt_handler(bringup_idt_table, X86_TRAP_VC, vc_boot_ghcb); + } bringup_idt_descr.address = (unsigned long)bringup_idt_table; native_load_idt(&bringup_idt_descr); diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c index e9ff13cd90b0..3aaef1a18ffe 100644 --- a/arch/x86/kernel/sev-shared.c +++ b/arch/x86/kernel/sev-shared.c @@ -68,7 +68,7 @@ static u64 get_hv_features(void) return GHCB_MSR_HV_FT_RESP_VAL(val); } -static void __maybe_unused snp_register_ghcb_early(unsigned long paddr) +static void snp_register_ghcb_early(unsigned long paddr) { unsigned long pfn = paddr >> PAGE_SHIFT; u64 val; diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index cb20fb0c608e..39c87469ee0b 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -41,7 +41,7 @@ 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; +static struct ghcb *boot_ghcb __section(".data"); /* Bitmap of SEV features supported by the hypervisor */ static u64 sev_hv_features __ro_after_init; @@ -647,15 +647,39 @@ static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt) return ret; } -/* - * This function runs on the first #VC exception after the kernel - * switched to virtual addresses. - */ -static bool __init sev_es_setup_ghcb(void) +static void snp_register_per_cpu_ghcb(void) { + struct sev_es_runtime_data *data; + struct ghcb *ghcb; + + data = this_cpu_read(runtime_data); + ghcb = &data->ghcb_page; + + snp_register_ghcb_early(__pa(ghcb)); +} + +void setup_ghcb(void) +{ + if (!cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) + return; + /* First make sure the hypervisor talks a supported protocol. */ if (!sev_es_negotiate_protocol()) - return false; + sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ); + + /* + * Check whether the runtime #VC exception handler is active. It uses + * the per-CPU GHCB page which is set up by sev_es_init_vc_handling(). + * + * If SNP is active, register the per-CPU GHCB page so that the runtime + * exception handler can use it. + */ + if (initial_vc_handler == (unsigned long)kernel_exc_vmm_communication) { + if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) + snp_register_per_cpu_ghcb(); + + return; + } /* * Clear the boot_ghcb. The first exception comes in before the bss @@ -666,7 +690,9 @@ static bool __init sev_es_setup_ghcb(void) /* Alright - Make the boot-ghcb public */ boot_ghcb = &boot_ghcb_page; - return true; + /* SNP guest requires that GHCB GPA must be registered. */ + if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) + snp_register_ghcb_early(__pa(&boot_ghcb_page)); } #ifdef CONFIG_HOTPLUG_CPU @@ -1397,10 +1423,6 @@ bool __init handle_vc_boot_ghcb(struct pt_regs *regs) 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(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ); - vc_ghcb_invalidate(boot_ghcb); result = vc_init_em_ctxt(&ctxt, regs, exit_code);