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    SubjectRe: [PATCH v3 73/75] x86/sev-es: Support CPU offline/online
    On Tue, Apr 28, 2020 at 05:17:23PM +0200, Joerg Roedel wrote:
    > 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. When the
    > hypervisor would deliver and SIPI is wakes up the VCPU instead.

    That last sentence needs fixing.

    Also, that explanation belongs as comment over sev_es_ap_hlt_loop()
    because commit messages are not that easy to find.

    > Signed-off-by: Joerg Roedel <jroedel@suse.de>
    > ---
    > arch/x86/include/uapi/asm/svm.h | 1 +
    > arch/x86/kernel/sev-es.c | 58 +++++++++++++++++++++++++++++++++
    > 2 files changed, 59 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 28725c38e6fb..00a5d0483730 100644
    > --- a/arch/x86/kernel/sev-es.c
    > +++ b/arch/x86/kernel/sev-es.c
    > @@ -32,6 +32,8 @@
    > #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
    >
    > @@ -448,6 +450,60 @@ 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();
    > +
    > + /* Wakup Signal? */

    "Wakeup"

    > + if (ghcb_is_valid_sw_exit_info_2(ghcb) &&
    > + ghcb->save.sw_exit_info_2 != 0)

    No need for the "!= 0".

    > + break;
    > + }
    > +
    > + sev_es_put_ghcb(&state);
    > +}

    ...

    --
    Regards/Gruss,
    Boris.

    https://people.kernel.org/tglx/notes-about-netiquette

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