On Fri, Jul 26, 2019 at 02:15:27PM +0800, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Cc: Nadav Amit <namit@xxxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> ---
> 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;
Copying the entire struct apic to snapshot two functions is funky,
explicitly capturing the two functions would be more intuitive.
Tangentially related, kvm_setup_pv_ipi() can be annotated __init,
which means the function snapshots can be __ro_after_init.
That being said, can't we just remove kvm_send_ipi_all() and
kvm_send_ipi_allbutself()? AFAICT, the variations that lead to shorthand
are only used when apic_use_ipi_shorthand is true. If that isn't the
case, fixing the callers in the APIC code seems like the correct thing to
do.
> 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_all(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
>
