Re: [PATCH v2 05/13] x86/irq: Reserve a per CPU IDT vector for posted MSIs
From: Jacob Pan
Date: Mon Apr 15 2024 - 16:40:15 EST
On Mon, 15 Apr 2024 11:53:58 -0700, Jacob Pan
<jacob.jun.pan@xxxxxxxxxxxxxxx> wrote:
> Hi Thomas,
>
> On Thu, 11 Apr 2024 18:51:14 +0200, Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> wrote:
>
> > On Fri, Apr 05 2024 at 15:31, Jacob Pan wrote:
> > > diff --git a/arch/x86/include/asm/irq_vectors.h
> > > b/arch/x86/include/asm/irq_vectors.h index d18bfb238f66..1ee00be8218d
> > > 100644 --- a/arch/x86/include/asm/irq_vectors.h
> > > +++ b/arch/x86/include/asm/irq_vectors.h
> > > @@ -97,9 +97,16 @@
> > >
> > > #define LOCAL_TIMER_VECTOR 0xec
> > >
> > > +/*
> > > + * Posted interrupt notification vector for all device MSIs delivered
> > > to
> > > + * the host kernel.
> > > + */
> > > +#define POSTED_MSI_NOTIFICATION_VECTOR 0xeb
> > > #define NR_VECTORS 256
> > >
> > > -#ifdef CONFIG_X86_LOCAL_APIC
> > > +#ifdef CONFIG_X86_POSTED_MSI
> > > +#define FIRST_SYSTEM_VECTOR
> > > POSTED_MSI_NOTIFICATION_VECTOR +#elif defined(CONFIG_X86_LOCAL_APIC)
> > > #define FIRST_SYSTEM_VECTOR LOCAL_TIMER_VECTOR
> > > #else
> > > #define FIRST_SYSTEM_VECTOR NR_VECTORS
> >
> > This is horrible and we had attempts before to make the system vector
> > space dense. They all did not work and making an exception for this is
> > not what we want.
> >
> > If we really care then we do it proper for _all_ of them. Something like
> > the uncompiled below. There is certainly a smarter way to do the build
> > thing, but my kbuild foo is rusty.
> I too had the concern of the wasting system vectors, but did not know how
> to fix it. But now your code below works well. Tested without KVM in
> .config to show the gaps:
>
> In VECTOR IRQ domain.
>
> BEFORE:
> System: 46: 0-31,50,235-236,244,246-255
>
> AFTER:
> System: 46: 0-31,50,241-242,245-255
>
> The only gap is MANAGED_IRQ_SHUTDOWN_VECTOR(243), which is expected on a
> running system.
>
> Verified in irqvectors.s: .ascii "->MANAGED_IRQ_SHUTDOWN_VECTOR $243
>
> POSTED MSI/first system vector moved up from 235 to 241 for this case.
>
> Will try to let tools/arch/x86/include/asm/irq_vectors.h also use it
> instead of manually copy over each time. Any suggestions greatly
> appreciated.
>
On a second thought, if we make system IRQ vector determined at compile
time based on different CONFIG options, will it break userspace tools such
as perf? More importantly the rule of not breaking userspace.
+Arnaldo
> > ---
> > --- a/arch/x86/Makefile
> > +++ b/arch/x86/Makefile
> > @@ -245,6 +245,7 @@ archscripts: scripts_basic
> >
> > archheaders:
> > $(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all
> > + $(Q)$(MAKE) $(build)=arch/x86/kernel/irqvectors all
> >
> > ###
> > # Kernel objects
> > --- a/arch/x86/include/asm/irq_vectors.h
> > +++ b/arch/x86/include/asm/irq_vectors.h
> > @@ -43,59 +43,46 @@
> > */
> > #define ISA_IRQ_VECTOR(irq) (((FIRST_EXTERNAL_VECTOR +
> > 16) & ~15) + irq)
> > +#ifndef __ASSEMBLY__
> > /*
> > - * Special IRQ vectors used by the SMP architecture, 0xf0-0xff
> > - *
> > - * some of the following vectors are 'rare', they are merged
> > - * into a single vector (CALL_FUNCTION_VECTOR) to save vector space.
> > - * TLB, reschedule and local APIC vectors are performance-critical.
> > + * Special IRQ vectors used by the SMP architecture, 0xff and downwards
> > */
> > +enum {
> > + __SPURIOUS_APIC_VECTOR,
> > + __ERROR_APIC_VECTOR,
> > + __RESCHEDULE_VECTOR,
> > + __CALL_FUNCTION_VECTOR,
> > + __CALL_FUNCTION_SINGLE_VECTOR,
> > + __THERMAL_APIC_VECTOR,
> > + __THRESHOLD_APIC_VECTOR,
> > + __REBOOT_VECTOR,
> > + __X86_PLATFORM_IPI_VECTOR,
> > + __IRQ_WORK_VECTOR,
> > + __DEFERRED_ERROR_VECTOR,
> >
> > -#define SPURIOUS_APIC_VECTOR 0xff
> > -/*
> > - * Sanity check
> > - */
> > -#if ((SPURIOUS_APIC_VECTOR & 0x0F) != 0x0F)
> > -# error SPURIOUS_APIC_VECTOR definition error
> > +#if IS_ENABLED(CONFIG_HYPERVISOR_GUEST)
> > + __HYPERVISOR_CALLBACK_VECTOR,
> > #endif
> >
> > -#define ERROR_APIC_VECTOR 0xfe
> > -#define RESCHEDULE_VECTOR 0xfd
> > -#define CALL_FUNCTION_VECTOR 0xfc
> > -#define CALL_FUNCTION_SINGLE_VECTOR 0xfb
> > -#define THERMAL_APIC_VECTOR 0xfa
> > -#define THRESHOLD_APIC_VECTOR 0xf9
> > -#define REBOOT_VECTOR 0xf8
> > -
> > -/*
> > - * Generic system vector for platform specific use
> > - */
> > -#define X86_PLATFORM_IPI_VECTOR 0xf7
> > -
> > -/*
> > - * IRQ work vector:
> > - */
> > -#define IRQ_WORK_VECTOR 0xf6
> > -
> > -/* 0xf5 - unused, was UV_BAU_MESSAGE */
> > -#define DEFERRED_ERROR_VECTOR 0xf4
> > -
> > -/* Vector on which hypervisor callbacks will be delivered */
> > -#define HYPERVISOR_CALLBACK_VECTOR 0xf3
> > -
> > -/* Vector for KVM to deliver posted interrupt IPI */
> > -#define POSTED_INTR_VECTOR 0xf2
> > -#define POSTED_INTR_WAKEUP_VECTOR 0xf1
> > -#define POSTED_INTR_NESTED_VECTOR 0xf0
> > -
> > -#define MANAGED_IRQ_SHUTDOWN_VECTOR 0xef
> > +#if IS_ENABLED(CONFIG_KVM)
> > + /* Vector for KVM to deliver posted interrupt IPI */
> > + __POSTED_INTR_VECTOR,
> > + __POSTED_INTR_WAKEUP_VECTOR,
> > + __POSTED_INTR_NESTED_VECTOR,
> > +#endif
> > + __MANAGED_IRQ_SHUTDOWN_VECTOR,
> >
> > #if IS_ENABLED(CONFIG_HYPERV)
> > -#define HYPERV_REENLIGHTENMENT_VECTOR 0xee
> > -#define HYPERV_STIMER0_VECTOR 0xed
> > + __HYPERV_REENLIGHTENMENT_VECTOR,
> > + __HYPERV_STIMER0_VECTOR,
> > #endif
> > + __LOCAL_TIMER_VECTOR,
> > +};
> > +#endif /* !__ASSEMBLY__ */
> >
> > -#define LOCAL_TIMER_VECTOR 0xec
> > +#ifndef COMPILE_OFFSETS
> > +#include <asm/irqvectors.h>
> > +#endif
> >
> > #define NR_VECTORS 256
> >
> > --- /dev/null
> > +++ b/arch/x86/kernel/irqvectors/Makefile
> > @@ -0,0 +1,11 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +irqvectors-file :=
> > arch/$(SRCARCH)/include/generated/asm/irqvectors.h +targets +=
> > arch/$(SRCARCH)/kernel/irqvectors/irqvectors.s +
> > +$(irqvectors-file): arch/$(SRCARCH)/kernel/irqvectors/irqvectors.s
> > FORCE
> > + $(call filechk,offsets,__ASM_IRQVECTORS_H__)
> > +
> > +PHONY += all
> > +all: $(irqvectors-file)
> > + @:
> > --- /dev/null
> > +++ b/arch/x86/kernel/irqvectors/irqvectors.c
> > @@ -0,0 +1,42 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#define COMPILE_OFFSETS
> > +
> > +#include <linux/kbuild.h>
> > +#include <asm/irq_vectors.h>
> > +
> > +#define VECNR(v) (0xFF - __##v)
> > +#define VECTOR(v) DEFINE(v, VECNR(v))
> > +
> > +static void __used common(void)
> > +{
> > + VECTOR(SPURIOUS_APIC_VECTOR);
> > + VECTOR(ERROR_APIC_VECTOR);
> > + VECTOR(RESCHEDULE_VECTOR);
> > + VECTOR(CALL_FUNCTION_VECTOR);
> > + VECTOR(CALL_FUNCTION_SINGLE_VECTOR);
> > + VECTOR(THERMAL_APIC_VECTOR);
> > + VECTOR(THRESHOLD_APIC_VECTOR);
> > + VECTOR(REBOOT_VECTOR);
> > + VECTOR(X86_PLATFORM_IPI_VECTOR);
> > + VECTOR(IRQ_WORK_VECTOR);
> > + VECTOR(DEFERRED_ERROR_VECTOR);
> > +
> > +#if IS_ENABLED(CONFIG_HYPERVISOR_GUEST)
> > + VECTOR(HYPERVISOR_CALLBACK_VECTOR);
> > +#endif
> > +
> > +#if IS_ENABLED(CONFIG_KVM)
> > + /* Vector for KVM to deliver posted interrupt IPI */
> > + VECTOR(POSTED_INTR_VECTOR);
> > + VECTOR(POSTED_INTR_WAKEUP_VECTOR);
> > + VECTOR(POSTED_INTR_NESTED_VECTOR);
> > +#endif
> > + VECTOR(MANAGED_IRQ_SHUTDOWN_VECTOR);
> > +
> > +#if IS_ENABLED(CONFIG_HYPERV)
> > + VECTOR(HYPERV_REENLIGHTENMENT_VECTOR);
> > + VECTOR(HYPERV_STIMER0_VECTOR);
> > +#endif
> > + VECTOR(LOCAL_TIMER_VECTOR);
> > +}
> > +
> >
> >
> >
>
>
> Thanks,
>
> Jacob
Thanks,
Jacob