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    Subject[PATCH v4 72/75] x86/sev-es: Support CPU offline/online
    Date
    From: Joerg Roedel <jroedel@suse.de>

    Add a play_dead handler when running under SEV-ES. This is needed
    because the hypervisor can't deliver an SIPI request to restart the AP.
    Instead the kernel has to issue a VMGEXIT to halt the VCPU until the
    hypervisor wakes it up again.

    Signed-off-by: Joerg Roedel <jroedel@suse.de>
    ---
    arch/x86/include/uapi/asm/svm.h | 1 +
    arch/x86/kernel/sev-es.c | 64 +++++++++++++++++++++++++++++++++
    2 files changed, 65 insertions(+)

    diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
    index a19ce9681ec2..20a05839dd9a 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_AP_HLT_LOOP 0x80000004
    #define SVM_VMGEXIT_AP_JUMP_TABLE 0x80000005
    #define SVM_VMGEXIT_SET_AP_JUMP_TABLE 0
    #define SVM_VMGEXIT_GET_AP_JUMP_TABLE 1
    diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
    index 370cf9bf2c88..b147d97856c3 100644
    --- a/arch/x86/kernel/sev-es.c
    +++ b/arch/x86/kernel/sev-es.c
    @@ -29,6 +29,8 @@
    #include <asm/processor.h>
    #include <asm/traps.h>
    #include <asm/svm.h>
    +#include <asm/smp.h>
    +#include <asm/cpu.h>

    #define DR7_RESET_VALUE 0x400

    @@ -531,6 +533,66 @@ static bool __init sev_es_setup_ghcb(void)
    return true;
    }

    +#ifdef CONFIG_HOTPLUG_CPU
    +static void sev_es_ap_hlt_loop(void)
    +{
    + struct ghcb_state state;
    + struct ghcb *ghcb;
    +
    + ghcb = sev_es_get_ghcb(&state);
    +
    + while (true) {
    + vc_ghcb_invalidate(ghcb);
    + ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_HLT_LOOP);
    + ghcb_set_sw_exit_info_1(ghcb, 0);
    + ghcb_set_sw_exit_info_2(ghcb, 0);
    +
    + sev_es_wr_ghcb_msr(__pa(ghcb));
    + VMGEXIT();
    +
    + /* Wakeup signal? */
    + if (ghcb_is_valid_sw_exit_info_2(ghcb) &&
    + ghcb->save.sw_exit_info_2)
    + break;
    + }
    +
    + sev_es_put_ghcb(&state);
    +}
    +
    +/*
    + * Play_dead handler when running under SEV-ES. This is needed because
    + * the hypervisor can't deliver an SIPI request to restart the AP.
    + * Instead the kernel has to issue a VMGEXIT to halt the VCPU until the
    + * hypervisor wakes it up again.
    + */
    +static void sev_es_play_dead(void)
    +{
    + play_dead_common();
    +
    + /* IRQs now disabled */
    +
    + sev_es_ap_hlt_loop();
    +
    + /*
    + * If we get here, the VCPU was woken up again. Jump to CPU
    + * startup code to get it back online.
    + */
    +
    + start_cpu();
    +}
    +#else /* CONFIG_HOTPLUG_CPU */
    +#define sev_es_play_dead native_play_dead
    +#endif /* CONFIG_HOTPLUG_CPU */
    +
    +#ifdef CONFIG_SMP
    +static void __init sev_es_setup_play_dead(void)
    +{
    + smp_ops.play_dead = sev_es_play_dead;
    +}
    +#else
    +static inline void sev_es_setup_play_dead(void) { }
    +#endif
    +
    static void __init sev_es_alloc_runtime_data(int cpu)
    {
    struct sev_es_runtime_data *data;
    @@ -575,6 +637,8 @@ void __init sev_es_init_vc_handling(void)
    sev_es_init_ghcb(cpu);
    sev_es_setup_vc_stacks(cpu);
    }
    +
    + sev_es_setup_play_dead();
    }

    static void __init vc_early_forward_exception(struct es_em_ctxt *ctxt)
    --
    2.27.0
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