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RE: [PATCH] intel-iommu: Set status bit after operation completed
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From: |
Duan, Zhenzhong |
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Subject: |
RE: [PATCH] intel-iommu: Set status bit after operation completed |
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Date: |
Mon, 13 Mar 2023 03:23:32 +0000 |
>-----Original Message-----
>From: Peter Xu <peterx@redhat.com>
>Sent: Friday, March 10, 2023 10:29 PM
>To: Duan, Zhenzhong <zhenzhong.duan@intel.com>
>Cc: qemu-devel@nongnu.org; mst@redhat.com; jasowang@redhat.com;
>pbonzini@redhat.com; richard.henderson@linaro.org; eduardo@habkost.net;
>marcel.apfelbaum@gmail.com
>Subject: Re: [PATCH] intel-iommu: Set status bit after operation completed
>
>On Fri, Mar 10, 2023 at 02:32:13AM +0000, Duan, Zhenzhong wrote:
>> I think it may break with special designed guest OS,
>> E.x: Imagine a guest write GCMD_REG and start a new thread to do further
>work.
>> New thread find status bit in GTS_REG set and go ahead, but the
>> address space switch may not finish yet if guest memory is big, which may
>trigger a potential race.
>
>IMHO it's fine. For MMIO QEMU takes the BQL so if another thread reads the
>status reg it should be serialized until the current vcpu finishes.
>
>See prepare_mmio_access(). Thanks,
You are right, just know this, thanks Peter.
Regards
Zhenzhong