linux-kernel - Re: [PATCH] KVM: X86: Use IPI shorthands in kvm guest when support

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Message-ID: <CANRm+CzTJ6dCv=NSHLGV-uWdaES2F0T7PXgu0LXXEsBCJ8mxEA@mail.gmail.com>
Date:   Fri, 26 Jul 2019 14:16:11 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Nadav Amit <namit@...are.com>
Subject: Re: [PATCH] KVM: X86: Use IPI shorthands in kvm guest when support

On Fri, 26 Jul 2019 at 14:10, Wanpeng Li <kernellwp@...il.com> wrote:
>
> From: Wanpeng Li <wanpengli@...cent.com>
>
> IPI shorthand is supported now by linux apic/x2apic driver, switch to
> IPI shorthand for all excluding self and all including self destination
> shorthand in kvm guest, to avoid splitting the target mask into serveral
> PV IPI hypercalls.
>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Cc: Sean Christopherson <sean.j.christopherson@...el.com>
> Cc: Nadav Amit <namit@...are.com>
> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> ---
> Note: rebase against tip tree's x86/apic branch
>
>  arch/x86/kernel/kvm.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index b7f34fe..87b73b8 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -34,7 +34,9 @@
>  #include <asm/hypervisor.h>
>  #include <asm/tlb.h>
>
> +static struct apic orig_apic;
>  static int kvmapf = 1;
> +DECLARE_STATIC_KEY_FALSE(apic_use_ipi_shorthand);
>
>  static int __init parse_no_kvmapf(char *arg)
>  {
> @@ -507,12 +509,18 @@ static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int vector)
>
>  static void kvm_send_ipi_allbutself(int vector)
>  {
> -       kvm_send_ipi_mask_allbutself(cpu_online_mask, vector);
> +       if (static_branch_likely(&apic_use_ipi_shorthand))
> +               orig_apic.send_IPI_allbutself(vector);
> +       else
> +               kvm_send_ipi_mask_allbutself(cpu_online_mask, vector);
>  }
>
>  static void kvm_send_ipi_all(int vector)
>  {
> -       __send_ipi_mask(cpu_online_mask, vector);
> +       if (static_branch_likely(&apic_use_ipi_shorthand))
> +               orig_apic.send_IPI_allbutself(vector);

Make a mistake here, just resend the patch.

> +       else
> +               __send_ipi_mask(cpu_online_mask, vector);
>  }
>
>  /*
> @@ -520,6 +528,8 @@ static void kvm_send_ipi_all(int vector)
>   */
>  static void kvm_setup_pv_ipi(void)
>  {
> +       orig_apic = *apic;
> +
>         apic->send_IPI_mask = kvm_send_ipi_mask;
>         apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
>         apic->send_IPI_allbutself = kvm_send_ipi_allbutself;
> --
> 2.7.4
>