Re: [patch 14/21] Xen-paravirt: Add XEN config options and disable unsupported config options.

Dan Hecht
2007-02-13T23:26:06Z

On 02/13/2007 02:17 PM, Jeremy Fitzhardinge wrote:
> The XEN config option enables the Xen paravirt_ops interface, which is
> installed when the kernel finds itself running under Xen. (By some
> as-yet fully defined mechanism, implemented in a future patch.)
>
> Xen is no longer a sub-architecture, so the X86_XEN subarch config
> option has gone.
>
> The disabled config options are:
> - PREEMPT: Xen doesn't support it
> - HZ: set to 100Hz for now, to cut down on VCPU context switch rate.
> This will be adapted to use tickless later.
> - kexec: not yet supported
>

I assume you plan to eventually get all this stuff working but just want
to prevent configurations that the Xen paravirt-ops isn't ready for at
the moment?

Instead can you do it this way:

config XEN
depends on PARAVIRT && !PREEMPT && HZ_100 && !DOUBLEFAULT && !KEXEC

thanks,
Dan

> Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
> Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
> Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
> Signed-off-by: Chris Wright <chrisw@sous-sol.org>
>
> ---
> arch/i386/Kconfig | 7 +++++--
> arch/i386/Kconfig.debug | 1 +
> arch/i386/xen/Kconfig | 10 ++++++++++
> kernel/Kconfig.hz | 4 ++--
> kernel/Kconfig.preempt | 1 +
> 5 files changed, 19 insertions(+), 4 deletions(-)
>
> ===================================================================
> --- a/arch/i386/Kconfig
> +++ b/arch/i386/Kconfig
> @@ -192,6 +192,8 @@ config PARAVIRT
> under a hypervisor, improving performance significantly.
> However, when run without a hypervisor the kernel is
> theoretically slower. If in doubt, say N.
> +
> +source "arch/i386/xen/Kconfig"
>
> config ACPI_SRAT
> bool
> @@ -298,12 +300,12 @@ config X86_UP_IOAPIC
>
> config X86_LOCAL_APIC
> bool
> - depends on X86_UP_APIC || ((X86_VISWS || SMP) && !X86_VOYAGER) || X86_GENERICARCH
> + depends on X86_UP_APIC || (((X86_VISWS || SMP) && !X86_VOYAGER) || X86_GENERICARCH)
> default y
>
> config X86_IO_APIC
> bool
> - depends on X86_UP_IOAPIC || (SMP && !(X86_VISWS || X86_VOYAGER)) || X86_GENERICARCH
> + depends on X86_UP_IOAPIC || ((SMP && !(X86_VISWS || X86_VOYAGER)) || X86_GENERICARCH)
> default y
>
> config X86_VISWS_APIC
> @@ -743,6 +745,7 @@ source kernel/Kconfig.hz
>
> config KEXEC
> bool "kexec system call"
> + depends on !XEN
> help
> kexec is a system call that implements the ability to shutdown your
> current kernel, and to start another kernel. It is like a reboot
> ===================================================================
> --- a/arch/i386/Kconfig.debug
> +++ b/arch/i386/Kconfig.debug
> @@ -79,6 +79,7 @@ config DOUBLEFAULT
> config DOUBLEFAULT
> default y
> bool "Enable doublefault exception handler" if EMBEDDED
> + depends on !XEN
> help
> This option allows trapping of rare doublefault exceptions that
> would otherwise cause a system to silently reboot. Disabling this
> ===================================================================
> --- /dev/null
> +++ b/arch/i386/xen/Kconfig
> @@ -0,0 +1,10 @@
> +#
> +# This Kconfig describes xen options
> +#
> +
> +config XEN
> + bool "Enable support for Xen hypervisor"
> + depends PARAVIRT
> + default y
> + help
> + This is the Linux Xen port.
> ===================================================================
> --- a/kernel/Kconfig.hz
> +++ b/kernel/Kconfig.hz
> @@ -3,7 +3,7 @@
> #
>
> choice
> - prompt "Timer frequency"
> + prompt "Timer frequency" if !XEN
> default HZ_250
> help
> Allows the configuration of the timer frequency. It is customary
> @@ -49,7 +49,7 @@ endchoice
>
> config HZ
> int
> - default 100 if HZ_100
> + default 100 if HZ_100 || XEN
> default 250 if HZ_250
> default 300 if HZ_300
> default 1000 if HZ_1000
> ===================================================================
> --- a/kernel/Kconfig.preempt
> +++ b/kernel/Kconfig.preempt
> @@ -35,6 +35,7 @@ config PREEMPT_VOLUNTARY
>
> config PREEMPT
> bool "Preemptible Kernel (Low-Latency Desktop)"
> + depends on !XEN
> help
> This option reduces the latency of the kernel by making
> all kernel code (that is not executing in a critical section)
>