On Wed, 2007-08-29 at 04:12 +1000, Rusty Russell wrote:
> On Mon, 2007-08-27 at 10:16 -0500, Anthony Liguori wrote:
> > This patch refactors the current hypercall infrastructure to better support live
> > migration and SMP. It eliminates the hypercall page by trapping the UD
> > exception that would occur if you used the wrong hypercall instruction for the
> > underlying architecture and replacing it with the right one lazily.
>
> It also reduces the number of hypercall args, which you don't mention
> here.
Oh yes, sorry.
> > + er = emulate_instruction(&svm->vcpu, kvm_run, 0, 0);
> > +
> > + /* we should only succeed here in the case of hypercalls which
> > + cannot generate an MMIO event. MMIO means that the emulator
> > + is mistakenly allowing an instruction that should generate
> > + a UD fault so it's a bug. */
> > + BUG_ON(er == EMULATE_DO_MMIO);
>
> This seems... unwise. Firstly we know our emulator is incomplete.
> Secondly an SMP guest can exploit this to crash the host.
This code is gone in v2.
> (Code is in two places).
>
> > +#define KVM_HYPERCALL ".byte 0x0f,0x01,0xc1"
Good point.
> A nice big comment would be nice here, I think. Note that this is big
> enough for both "int $0x1f" and "sysenter", so I'm happy.
I need to add a comment somewhere mentioning that if you patch with
something less than 3 bytes, then you should pad with nop but the
hypervisor must treat the whole instruction (including the padding) as
atomic (that is, regardless of hypercall size, eip += 3) or you run the
risk of breakage during migration.
Regards,
Anthony Liguori
> Cheers,
> Rusty.
>
>
> -------------------------------------------------------------------------
> This SF.net email is sponsored by: Splunk Inc.
> Still grepping through log files to find problems? Stop.
> Now Search log events and configuration files using AJAX and a browser.
> Download your FREE copy of Splunk now >> http://get.splunk.com/
> _______________________________________________
> kvm-devel mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/kvm-devel
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
