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Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic |
Date: |
Sat, 27 Apr 2013 14:12:16 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 |
Il 27/04/2013 12:09, Blue Swirl ha scritto:
> On Fri, Apr 26, 2013 at 10:13 PM, Paolo Bonzini <address@hidden> wrote:
>> Il 26/04/2013 19:46, Igor Mammedov ha scritto:
>>>>> But as the address can't be changed (yet), the entire patch could be
>>>>> simply:
>>>>> - kioapic->base_address = s->busdev.mmio[0].addr;
>>>>> + kioapic->base_address = IO_APIC_DEFAULT_ADDRESS;
>>> It's a bit fragile, but that for sure simpler and can work.
>>>
>>> Jan, Paolo,
>>> Are you ok with this approach?
>>>
>>
>> I think extending memory_region_find is a good idea anyway, and at this
>> point I don't see a reason to do the above change...
>
> The reasoning was in the part that Igor cut off:
>
> "Later, when it's possible to change the address via PIIX3 registers,
> we can adjust the base and pass that properly to kioapic and on to
> KVM.
>
> Resolving the base address every time when kvm_ioapic_put() is called
> is also less efficient, assuming of course that the base address
> changes less often than the KVM ioctl is used."
>
> I think the patch is a bit flawed. If the guest maps something else on
> top of IOAPIC, like LAPIC (which should be in CPU specific address
> spaces, but for now it lives in the global system memory space), the
> guest could trigger the abort() by resetting the system.
The questions are, in order of importance:
(1) what privileges would this require in the guest? Answer: a lot.
(2) is this likely to happen by chance? Answer: no, not at all.
(3) is there a workaround? Answer: yes, disable in-kernel irqchip.
Simply setting IO_APIC_DEFAULT_ADDRESS is also flawed in my opinion.
I'm not sure the in-kernel irqchip handles correctly an overlap between
the IOAPIC and LAPIC regions, maybe an abort is predictable after all.
Paolo
- Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic, (continued)
[Qemu-devel] [PATCH 15/19 v2] extend memory_region_find() and use it in kvm/ioapic, Igor Mammedov, 2013/04/24
Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic, Blue Swirl, 2013/04/25
- Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic, Igor Mammedov, 2013/04/26
- Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic, Blue Swirl, 2013/04/26
- Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic, Igor Mammedov, 2013/04/26
- Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic, Paolo Bonzini, 2013/04/26
- Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic, Blue Swirl, 2013/04/27
- Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic, Blue Swirl, 2013/04/27
- Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic, Paolo Bonzini, 2013/04/29
- Re: [Qemu-devel] [PATCH 17/21] introduce memory_region_get_address() and use it in kvm/ioapic, Igor Mammedov, 2013/04/29
[Qemu-devel] [PATCH 04/21] cpu: resume CPU from CPUClass.cpu_common_realizefn() when it is hot-plugged, Igor Mammedov, 2013/04/23
[Qemu-devel] [PATCH 06/21] target-i386: pc: update rtc_cmos on CPU hot-plug, Igor Mammedov, 2013/04/23
[Qemu-devel] [PATCH 05/21] introduce CPU hot-plug notifier, Igor Mammedov, 2013/04/23