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    Subject[PATCH v3 74/75] x86/sev-es: Handle NMI State
    Date
    From: Joerg Roedel <jroedel@suse.de>

    When running under SEV-ES the kernel has to tell the hypervisor when to
    open the NMI window again after an NMI was injected. This is done with
    an NMI-complete message to the hypervisor.

    Add code to the kernels NMI handler to send this message right at the
    beginning of do_nmi(). This always allows nesting NMIs.

    Signed-off-by: Joerg Roedel <jroedel@suse.de>
    ---
    arch/x86/include/asm/sev-es.h | 2 ++
    arch/x86/include/uapi/asm/svm.h | 1 +
    arch/x86/kernel/nmi.c | 7 +++++++
    arch/x86/kernel/sev-es.c | 18 ++++++++++++++++++
    4 files changed, 28 insertions(+)

    diff --git a/arch/x86/include/asm/sev-es.h b/arch/x86/include/asm/sev-es.h
    index c89b6e2e6439..a242d16727f1 100644
    --- a/arch/x86/include/asm/sev-es.h
    +++ b/arch/x86/include/asm/sev-es.h
    @@ -86,6 +86,7 @@ const char *vc_stack_name(enum stack_type type);
    void sev_es_nmi_enter(void);
    void sev_es_nmi_exit(void);
    int sev_es_setup_ap_jump_table(struct real_mode_header *rmh);
    +void sev_es_nmi_complete(void);
    #else /* CONFIG_AMD_MEM_ENCRYPT */
    static inline const char *vc_stack_name(enum stack_type type)
    {
    @@ -95,6 +96,7 @@ static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh)
    {
    return 0;
    }
    +static inline void sev_es_nmi_complete(void) { }
    #endif /* CONFIG_AMD_MEM_ENCRYPT*/

    #endif
    diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
    index 20a05839dd9a..0f837339db66 100644
    --- a/arch/x86/include/uapi/asm/svm.h
    +++ b/arch/x86/include/uapi/asm/svm.h
    @@ -84,6 +84,7 @@
    /* SEV-ES software-defined VMGEXIT events */
    #define SVM_VMGEXIT_MMIO_READ 0x80000001
    #define SVM_VMGEXIT_MMIO_WRITE 0x80000002
    +#define SVM_VMGEXIT_NMI_COMPLETE 0x80000003
    #define SVM_VMGEXIT_AP_HLT_LOOP 0x80000004
    #define SVM_VMGEXIT_AP_JUMP_TABLE 0x80000005
    #define SVM_VMGEXIT_SET_AP_JUMP_TABLE 0
    diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
    index 27d1016ec840..8898002e5600 100644
    --- a/arch/x86/kernel/nmi.c
    +++ b/arch/x86/kernel/nmi.c
    @@ -511,6 +511,13 @@ NOKPROBE_SYMBOL(is_debug_stack);
    dotraplinkage notrace void
    do_nmi(struct pt_regs *regs, long error_code)
    {
    + /*
    + * Re-enable NMIs right here when running as an SEV-ES guest. This might
    + * cause nested NMIs, but those can be handled safely.
    + */
    + if (sev_es_active())
    + sev_es_nmi_complete();
    +
    if (IS_ENABLED(CONFIG_SMP) && cpu_is_offline(smp_processor_id()))
    return;

    diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
    index 00a5d0483730..eef6e2196ef4 100644
    --- a/arch/x86/kernel/sev-es.c
    +++ b/arch/x86/kernel/sev-es.c
    @@ -341,6 +341,24 @@ static phys_addr_t vc_slow_virt_to_phys(struct ghcb *ghcb, unsigned long vaddr)
    /* Include code shared with pre-decompression boot stage */
    #include "sev-es-shared.c"

    +void sev_es_nmi_complete(void)
    +{
    + struct ghcb_state state;
    + struct ghcb *ghcb;
    +
    + ghcb = sev_es_get_ghcb(&state);
    +
    + vc_ghcb_invalidate(ghcb);
    + ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_NMI_COMPLETE);
    + ghcb_set_sw_exit_info_1(ghcb, 0);
    + ghcb_set_sw_exit_info_2(ghcb, 0);
    +
    + sev_es_wr_ghcb_msr(__pa(ghcb));
    + VMGEXIT();
    +
    + sev_es_put_ghcb(&state);
    +}
    +
    static u64 sev_es_get_jump_table_addr(void)
    {
    struct ghcb_state state;
    --
    2.17.1
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