|
|
![](http://www.xen.org/images/globals/pixel.gif) |
|
|
|
|
|
|
|
xen-devel
[Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops)
Ingo Molnar wrote:
Since they are not performance critical, then why doesnt Xen catch
the IO-APIC accesses, and virtualizes the device?
If you want to hook into the IO-APIC code at such a low level, why
dont you hook into the _hardware_ API - i.e. catch those
setup/routing modifications to the IO-APIC space. No Linux changes
are needed in that case.
Yes, these changes aren't for a performance reason. It's a case where a
few lines change in Linux saves many hundreds or thousands of lines
change in Xen.
Xen doesn't have an internal mechanism for emulating devices via
pagefaults (that's generally handled by a qemu instance running as part
of a guest domain), so there's no mechanism to map and emulate the
io-apic. Putting such support into Xen would mean adding a pile of new
infrastructure to support this case.
Unlike the mtrr discussion, where the msr read/write ops would allow us
to emulate the mtrr within the Xen-specific parts of the kernel, the
io-apic ops are just accessed via normal memory writes which we can't
hook, so it would have to be done within Xen.
The other thing I thought about was putting a hook in the Linux
pagefault handler, so we could emulate the ioapic at that level. But
putting a hook in a very hot path to avoid code changes in a cold path
doesn't make any sense. (Same applies to doing PF emulation within Xen;
that's an even hotter path than Linux's.)
J
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
|
<Prev in Thread] |
Current Thread |
[Next in Thread>
|
- [Xen-devel] [PATCH 08/17] xen: direct irq registration to pirq event channels, (continued)
- [Xen-devel] [PATCH 08/17] xen: direct irq registration to pirq event channels, Jeremy Fitzhardinge
- [Xen-devel] [PATCH 05/17] xen: implement pirq type event channels, Jeremy Fitzhardinge
- [Xen-devel] [PATCH 11/17] xen: don't setup acpi interrupt unless there is one, Jeremy Fitzhardinge
- [Xen-devel] [PATCH 13/17] xen: initialize irq 0 too, Jeremy Fitzhardinge
- [Xen-devel] [PATCH 10/17] xen: pre-initialize legacy irqs early, Jeremy Fitzhardinge
- [Xen-devel] [PATCH 14/17] xen: dynamically allocate irq & event structures, Jeremy Fitzhardinge
- [Xen-devel] [PATCH 15/17] xen: set pirq name to something useful., Jeremy Fitzhardinge
- [Xen-devel] [PATCH 16/17] xen: fix legacy irq setup, make ioapic-less machines work., Jeremy Fitzhardinge
- [Xen-devel] [PATCH 17/17] xen: disable MSI, Jeremy Fitzhardinge
- [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops), Ingo Molnar
- [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops),
Jeremy Fitzhardinge <=
- [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops), Ingo Molnar
- Re: [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops), George Dunlap
- Re: [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops), Avi Kivity
- RE: [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops), Dan Magenheimer
- Re: [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops), Avi Kivity
- Re: [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops), Ingo Molnar
- Re: [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops), Jeremy Fitzhardinge
- RE: [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops), Dan Magenheimer
- Distro kernel and 'virtualization server' vs. 'server that sometimes runs virtual instances' rant (was: Re: [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops)), Luke S Crawford
- Re: Distro kernel and 'virtualization server' vs. 'server that sometimes runs virtual instances' rant (was: Re: [Xen-devel] Re: [GIT PULL] Xen APIC hooks (with io_apic_ops)), Tim Post
|
|
|
|
|