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 use a consistent and/or specific GPA for the GHCB associated with a vCPU. For more information, see the GHCB specification section "GHCB GPA Registration". Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx> --- arch/x86/include/asm/sev.h | 2 + arch/x86/kernel/cpu/common.c | 4 ++ arch/x86/kernel/head64.c | 1 + arch/x86/kernel/sev-shared.c | 2 +- arch/x86/kernel/sev.c | 120 ++++++++++++++++++++--------------- 5 files changed, 77 insertions(+), 52 deletions(-) diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index e37451849165..0df508374a35 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 sev_snp_register_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 sev_snp_register_ghcb(void) { } #endif #endif diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 0663642d6199..1146e8920b03 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -59,6 +59,7 @@ #include <asm/cpu_device_id.h> #include <asm/uv/uv.h> #include <asm/sigframe.h> +#include <asm/sev.h> #include "cpu.h" @@ -1988,6 +1989,9 @@ void cpu_init_exception_handling(void) load_TR_desc(); + /* Register the GHCB before taking any VC exception */ + sev_snp_register_ghcb(); + /* Finally load the IDT */ load_current_idt(); } diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index b01f64e8389b..fa02402dcb9b 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -588,6 +588,7 @@ void early_setup_idt(void) bringup_idt_descr.address = (unsigned long)bringup_idt_table; native_load_idt(&bringup_idt_descr); + sev_snp_register_ghcb(); } /* 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 a0cada8398a4..17ad603f62da 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -162,55 +162,6 @@ void noinstr __sev_es_ist_exit(void) this_cpu_write(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC], *(unsigned long *)ist); } -/* - * Nothing shall interrupt this code path while holding the per-CPU - * GHCB. The backup GHCB is only for NMIs interrupting this path. - * - * Callers must disable local interrupts around it. - */ -static noinstr struct ghcb *__sev_get_ghcb(struct ghcb_state *state) -{ - struct sev_es_runtime_data *data; - struct ghcb *ghcb; - - WARN_ON(!irqs_disabled()); - - data = this_cpu_read(runtime_data); - ghcb = &data->ghcb_page; - - if (unlikely(data->ghcb_active)) { - /* GHCB is already in use - save its contents */ - - if (unlikely(data->backup_ghcb_active)) { - /* - * Backup-GHCB is also already in use. There is no way - * to continue here so just kill the machine. To make - * panic() work, mark GHCBs inactive so that messages - * can be printed out. - */ - data->ghcb_active = false; - data->backup_ghcb_active = false; - - instrumentation_begin(); - panic("Unable to handle #VC exception! GHCB and Backup GHCB are already in use"); - instrumentation_end(); - } - - /* Mark backup_ghcb active before writing to it */ - data->backup_ghcb_active = true; - - state->ghcb = &data->backup_ghcb; - - /* Backup GHCB content */ - *state->ghcb = *ghcb; - } else { - state->ghcb = NULL; - data->ghcb_active = true; - } - - return ghcb; -} - static inline u64 sev_es_rd_ghcb_msr(void) { return __rdmsr(MSR_AMD64_SEV_ES_GHCB); @@ -484,6 +435,55 @@ static enum es_result vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt /* Include code shared with pre-decompression boot stage */ #include "sev-shared.c" +/* + * Nothing shall interrupt this code path while holding the per-CPU + * GHCB. The backup GHCB is only for NMIs interrupting this path. + * + * Callers must disable local interrupts around it. + */ +static noinstr struct ghcb *__sev_get_ghcb(struct ghcb_state *state) +{ + struct sev_es_runtime_data *data; + struct ghcb *ghcb; + + WARN_ON(!irqs_disabled()); + + data = this_cpu_read(runtime_data); + ghcb = &data->ghcb_page; + + if (unlikely(data->ghcb_active)) { + /* GHCB is already in use - save its contents */ + + if (unlikely(data->backup_ghcb_active)) { + /* + * Backup-GHCB is also already in use. There is no way + * to continue here so just kill the machine. To make + * panic() work, mark GHCBs inactive so that messages + * can be printed out. + */ + data->ghcb_active = false; + data->backup_ghcb_active = false; + + instrumentation_begin(); + panic("Unable to handle #VC exception! GHCB and Backup GHCB are already in use"); + instrumentation_end(); + } + + /* Mark backup_ghcb active before writing to it */ + data->backup_ghcb_active = true; + + state->ghcb = &data->backup_ghcb; + + /* Backup GHCB content */ + *state->ghcb = *ghcb; + } else { + state->ghcb = NULL; + data->ghcb_active = true; + } + + return ghcb; +} + static noinstr void __sev_put_ghcb(struct ghcb_state *state) { struct sev_es_runtime_data *data; @@ -652,7 +652,7 @@ static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt) * This function runs on the first #VC exception after the kernel * switched to virtual addresses. */ -static bool __init sev_es_setup_ghcb(void) +static bool __init setup_ghcb(void) { /* First make sure the hypervisor talks a supported protocol. */ if (!sev_es_negotiate_protocol()) @@ -667,6 +667,10 @@ static bool __init sev_es_setup_ghcb(void) /* Alright - Make the boot-ghcb public */ boot_ghcb = &boot_ghcb_page; + /* SEV-SNP guest requires that GHCB GPA must be registered. */ + if (cc_platform_has(CC_ATTR_SEV_SNP)) + snp_register_ghcb_early(__pa(&boot_ghcb_page)); + return true; } @@ -758,6 +762,20 @@ static void __init init_ghcb(int cpu) data->backup_ghcb_active = false; } +void sev_snp_register_ghcb(void) +{ + struct sev_es_runtime_data *data; + struct ghcb *ghcb; + + if (!cc_platform_has(CC_ATTR_SEV_SNP)) + return; + + data = this_cpu_read(runtime_data); + ghcb = &data->ghcb_page; + + snp_register_ghcb_early(__pa(ghcb)); +} + void __init sev_es_init_vc_handling(void) { int cpu; @@ -1400,7 +1418,7 @@ bool __init handle_vc_boot_ghcb(struct pt_regs *regs) enum es_result result; /* Do initial setup or terminate the guest */ - if (unlikely(boot_ghcb == NULL && !sev_es_setup_ghcb())) + if (unlikely(boot_ghcb == NULL && !setup_ghcb())) sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ); vc_ghcb_invalidate(boot_ghcb); -- 2.25.1