When sending an IPI to a single CPU there is no need to deal with cpumasks.
With 2 CPU guest on WS2019 a minor (like 3%, 8043 -> 7761 CPU cycles)
improvement with smp_call_function_single() loop benchmark can be seeb. The
optimization, however, is tiny and straitforward. Also, send_ipi_one() is
important for PV spinlock kick.
Switching to the regular APIC IPI send for CPU > 64 case does not make
sense as it is twice as expesive (12650 CPU cycles for __send_ipi_mask_ex()
call, 26000 for orig_apic.send_IPI(cpu, vector)).
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Link: https://lkml.kernel.org/r/20191027151938.7296-1-vkuznets@redhat.com
Now that there's Hyper-V IOMMU driver, Linux can switch to x2apic mode
when supported by the vcpus.
However, the apic access functions for Hyper-V enlightened apic assume
xapic mode only.
As a result, Linux fails to bring up secondary cpus when run as a guest
in QEMU/KVM with both hv_apic and x2apic enabled.
According to Michael Kelley, when in x2apic mode, the Hyper-V synthetic
apic MSRs behave exactly the same as the corresponding architectural
x2apic MSRs, so there's no need to override the apic accessors. The
only exception is hv_apic_eoi_write, which benefits from lazy EOI when
available; however, its implementation works for both xapic and x2apic
modes.
Fixes: 29217a4746 ("iommu/hyper-v: Add Hyper-V stub IOMMU driver")
Fixes: 6b48cb5f83 ("X86/Hyper-V: Enlighten APIC access")
Suggested-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20191010123258.16919-1-rkagan@virtuozzo.com
These structures are going to be used from KVM code so let's make
their names reflect their Hyper-V origin.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Acked-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The Hyper-V APIC code is built when CONFIG_HYPERV is enabled but the actual
code in that file is guarded with CONFIG_X86_64. There is no point in doing
this. Neither is there a point in having the CONFIG_HYPERV guard in there
because the containing directory is not built when CONFIG_HYPERV=n.
Further for the hv_init_apic() function a stub is provided only for
CONFIG_HYPERV=n, which is pointless as the callsite is not compiled at
all. But for X86_32 the stub is missing and the build fails.
Clean that up:
- Compile hv_apic.c only when CONFIG_X86_64=y
- Make the stub for hv_init_apic() available when CONFG_X86_64=n
Fixes: 6b48cb5f83 ("X86/Hyper-V: Enlighten APIC access")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Michael Kelley <mikelley@microsoft.com>
Not all configurations magically include asm/apic.h, but the Hyper-V code
requires it. Include it explicitely.
Fixes: 6b48cb5f83 ("X86/Hyper-V: Enlighten APIC access")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Michael Kelley <mikelley@microsoft.com>
