[PATCH] KVM: X86: Use IPI shorthands in kvm guest when support

[PATCH] KVM: X86: Use IPI shorthands in kvm guest when support

[Wanpeng Li]

From: Wanpeng Li <wanpengli@tencent.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@linutronix.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Nadav Amit <namit@vmware.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.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);
+	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

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

[Wanpeng Li]

On Fri, 26 Jul 2019 at 14:10, Wanpeng Li <kernellwp@gmail.com> wrote:
>
> From: Wanpeng Li <wanpengli@tencent.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@linutronix.de>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Sean Christopherson <sean.j.christopherson@intel.com>
> Cc: Nadav Amit <namit@vmware.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.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
>

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

[Thomas Gleixner]

On Fri, 26 Jul 2019, Wanpeng Li wrote:
> On Fri, 26 Jul 2019 at 14:10, Wanpeng Li <kernellwp@gmail.com> wrote:
> >  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.

Please don't use [RESEND] if the patch is different. Use [PATCH v2].

[RESEND] is used when you actually resend an unmodified patch, e.g. when
the first submission was ignored for a longer time.

Thanks,

	tglx

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

[Wanpeng Li]

On Fri, 26 Jul 2019 at 15:20, Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Fri, 26 Jul 2019, Wanpeng Li wrote:
> > On Fri, 26 Jul 2019 at 14:10, Wanpeng Li <kernellwp@gmail.com> wrote:
> > >  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.
>
> Please don't use [RESEND] if the patch is different. Use [PATCH v2].
>
> [RESEND] is used when you actually resend an unmodified patch, e.g. when
> the first submission was ignored for a longer time.

Will do for next time, I guess Paolo can still review the [RESEND] one
for this time to avoid my patch flush the mailing list. :)

Regards,
Wanpeng Li

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

[kbuild test robot]

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Hi Wanpeng,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[cannot apply to v5.3-rc1 next-20190726]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Wanpeng-Li/KVM-X86-Use-IPI-shorthands-in-kvm-guest-when-support/20190726-201453
config: x86_64-rhel (attached as .config)
compiler: gcc-7 (Debian 7.4.0-10) 7.4.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> ld: arch/x86/kernel/kvm.o:(__jump_table+0x8): undefined reference to `apic_use_ipi_shorthand'
   ld: arch/x86/kernel/kvm.o:(__jump_table+0x18): undefined reference to `apic_use_ipi_shorthand'

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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