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    Subject[PATCH v2 09/12] x86/sev: Use AP Jump Table blob to stop CPU
    Date
    From: Joerg Roedel <jroedel@suse.de>

    To support kexec under SEV-ES the APs can't be parked with HLT. Upon
    wakeup the AP needs to find its way to execute at the reset vector set
    by the new kernel and in real-mode.

    This is what the AP Jump Table blob provides, so stop the APs the
    SEV-ES way by calling the AP-reset-hold VMGEXIT from the AP Jump
    Table.

    Signed-off-by: Joerg Roedel <jroedel@suse.de>
    ---
    arch/x86/include/asm/sev.h | 7 +++++++
    arch/x86/kernel/process.c | 8 ++++++++
    arch/x86/kernel/sev.c | 11 ++++++++++-
    3 files changed, 25 insertions(+), 1 deletion(-)

    diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
    index 134a7c9d91b6..cd14b6e10f12 100644
    --- a/arch/x86/include/asm/sev.h
    +++ b/arch/x86/include/asm/sev.h
    @@ -81,12 +81,19 @@ static __always_inline void sev_es_nmi_complete(void)
    __sev_es_nmi_complete();
    }
    extern int __init sev_es_efi_map_ghcbs(pgd_t *pgd);
    +void __sev_es_stop_this_cpu(void);
    +static __always_inline void sev_es_stop_this_cpu(void)
    +{
    + if (static_branch_unlikely(&sev_es_enable_key))
    + __sev_es_stop_this_cpu();
    +}
    #else
    static inline void sev_es_ist_enter(struct pt_regs *regs) { }
    static inline void sev_es_ist_exit(void) { }
    static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh) { return 0; }
    static inline void sev_es_nmi_complete(void) { }
    static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }
    +static inline void sev_es_stop_this_cpu(void) { }
    #endif

    #endif
    diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
    index 1d9463e3096b..8d9b03923baa 100644
    --- a/arch/x86/kernel/process.c
    +++ b/arch/x86/kernel/process.c
    @@ -43,6 +43,7 @@
    #include <asm/io_bitmap.h>
    #include <asm/proto.h>
    #include <asm/frame.h>
    +#include <asm/sev.h>

    #include "process.h"

    @@ -752,6 +753,13 @@ void stop_this_cpu(void *dummy)
    if (boot_cpu_has(X86_FEATURE_SME))
    native_wbinvd();
    for (;;) {
    + /*
    + * SEV-ES guests need a special stop routine to support
    + * kexec. Try this first, if it fails the function will
    + * return and native_halt() is used.
    + */
    + sev_es_stop_this_cpu();
    +
    /*
    * Use native_halt() so that memory contents don't change
    * (stack usage and variables) after possibly issuing the
    diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
    index 20b439986d86..bac9bb4fa54e 100644
    --- a/arch/x86/kernel/sev.c
    +++ b/arch/x86/kernel/sev.c
    @@ -695,7 +695,6 @@ static bool __init sev_es_setup_ghcb(void)
    return true;
    }

    -#ifdef CONFIG_HOTPLUG_CPU
    void __noreturn sev_jumptable_ap_park(void)
    {
    local_irq_disable();
    @@ -725,6 +724,16 @@ void __noreturn sev_jumptable_ap_park(void)
    }
    STACK_FRAME_NON_STANDARD(sev_jumptable_ap_park);

    +void __sev_es_stop_this_cpu(void)
    +{
    + /* Only park in the AP Jump Table when the code has been installed */
    + if (!sev_ap_jumptable_blob_installed)
    + return;
    +
    + sev_jumptable_ap_park();
    +}
    +
    +#ifdef CONFIG_HOTPLUG_CPU
    static void sev_es_ap_hlt_loop(void)
    {
    struct ghcb_state state;
    --
    2.33.0
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