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Re: xen spl rework
On Tue, 20 Dec 2011 00:57:13 +0530, Cherry G. Mathew wrote:
I've reworked the spl code in XEN to use a single entry point into C
code, and to optimise the pending event processing via spllower()
- remove hypervisor_enable_ipl from headers, it does not seem to be
- if you are in a cleanup process, have a consistent clear/set
interrupt flag function for x86 and xen. Use x86_enable/disable_intr()
stubs, and do not spread cli()/sti() directly. It's easier to grep/grok
for x86_ variants.
- regarding XXX comments:
/* XXX: Don't need to save everything. Just the callee saved
* regs and stuff that hardclock() needs
You are correct, however keep in mind that you may call C functions
that do not make any assumption regarding registers' usage (like
xspllower), so it's still better to be conservative there and save all
general purpose regs.
- please document xspllower() vs Xspllower() use (comments are enough).
One question: what's the reason behind removing the IPL recurse/remove
code? Interesting stuff nonetheless, I think that this will fix a very
rare issue I had with an old machine where I could trigger double faults
on Xen thanks to this.
I'd love for as much test reportage as possible with this patch.
dom0 is reported to hang on launching domUs. I'd like this verified
PAE kernels if possible.
If I can spare some cycles on my host, I'll do it this week. Else that
will just be a VM test until January, I am afraid.
Please include relevant dmesg/console output.
tech-kern@ is Cc:ed for more eyes to see if I've missed anything
port-i386/amd64@ is Cc:ed because I've removed some of the common
assembler bits from the XEN path and added some new. Review would be
useful. I'm hoping this doesn't affect anything for non-XEN.
Untangling the #ifdef XEN hell is a good step, but please be aware that
you are making modifications in highly sensitive code path (performance
and security) . So a peer review won't just be enough, you will also
have to test it extensively on your side too, and maybe ask core/port
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