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From: Paolo Bonzini <pbonzini@redhat.com>
To: Shannon Zhao <zhaoshenglong@huawei.com>,
	qemu-devel@nongnu.org, guangrong.xiao@gmail.com
Cc: shannon.zhaosl@gmail.com, kvmarm@lists.cs.columbia.edu,
	kvm@vger.kernel.org
Subject: Re: [PATCH] kvm: Delete the slot only when KVM_MEM_READONLY flag is changed
Date: Wed, 13 Jun 2018 17:58:18 +0200	[thread overview]
Message-ID: <fdd4182f-6f7c-16ae-e800-3219bf1d09e9@redhat.com> (raw)
In-Reply-To: <5B207E41.3080209@huawei.com>

On 13/06/2018 04:15, Shannon Zhao wrote:
> 
> 
> On 2018/6/12 20:17, Paolo Bonzini wrote:
>> On 16/05/2018 11:18, Shannon Zhao wrote:
>>> According to KVM commit 75d61fbc, it needs to delete the slot before
>>> changing the KVM_MEM_READONLY flag. But QEMU commit 235e8982 only check
>>> whether KVM_MEM_READONLY flag is set instead of changing. It doesn't
>>> need to delete the slot if the KVM_MEM_READONLY flag is not changed.
>>>
>>> This fixes a issue that migrating a VM at the OVMF startup stage and
>>> VM is executing the codes in rom. Between the deleting and adding the
>>> slot in kvm_set_user_memory_region, there is a chance that guest access
>>> rom and trap to KVM, then KVM can't find the corresponding memslot.
>>> While KVM (on ARM) injects an abort to guest due to the broken hva, then
>>> guest will get stuck.
>>>
>>> Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
>>
>> I'm a bit worried about old_flags not being set on all paths to
>> kvm_set_user_memory_region.  This would lead to extra
>> KVM_SET_USER_MEMORY_REGION calls.  It should not be a problem but
>> it is ugly.  Does something like the additional changes below work for you?
>>
> I test below patch. It works for our testcase.
> Do I need to fold them into one and resend?

No need to, thanks!

Paolo

WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Shannon Zhao <zhaoshenglong@huawei.com>,
	qemu-devel@nongnu.org, guangrong.xiao@gmail.com
Cc: shannon.zhaosl@gmail.com, kvmarm@lists.cs.columbia.edu,
	kvm@vger.kernel.org
Subject: Re: [Qemu-devel] [PATCH] kvm: Delete the slot only when KVM_MEM_READONLY flag is changed
Date: Wed, 13 Jun 2018 17:58:18 +0200	[thread overview]
Message-ID: <fdd4182f-6f7c-16ae-e800-3219bf1d09e9@redhat.com> (raw)
In-Reply-To: <5B207E41.3080209@huawei.com>

On 13/06/2018 04:15, Shannon Zhao wrote:
> 
> 
> On 2018/6/12 20:17, Paolo Bonzini wrote:
>> On 16/05/2018 11:18, Shannon Zhao wrote:
>>> According to KVM commit 75d61fbc, it needs to delete the slot before
>>> changing the KVM_MEM_READONLY flag. But QEMU commit 235e8982 only check
>>> whether KVM_MEM_READONLY flag is set instead of changing. It doesn't
>>> need to delete the slot if the KVM_MEM_READONLY flag is not changed.
>>>
>>> This fixes a issue that migrating a VM at the OVMF startup stage and
>>> VM is executing the codes in rom. Between the deleting and adding the
>>> slot in kvm_set_user_memory_region, there is a chance that guest access
>>> rom and trap to KVM, then KVM can't find the corresponding memslot.
>>> While KVM (on ARM) injects an abort to guest due to the broken hva, then
>>> guest will get stuck.
>>>
>>> Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
>>
>> I'm a bit worried about old_flags not being set on all paths to
>> kvm_set_user_memory_region.  This would lead to extra
>> KVM_SET_USER_MEMORY_REGION calls.  It should not be a problem but
>> it is ugly.  Does something like the additional changes below work for you?
>>
> I test below patch. It works for our testcase.
> Do I need to fold them into one and resend?

No need to, thanks!

Paolo

  reply	other threads:[~2018-06-13 15:58 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-16  9:18 [PATCH] kvm: Delete the slot only when KVM_MEM_READONLY flag is changed Shannon Zhao
2018-05-16  9:18 ` Shannon Zhao
2018-05-16  9:18 ` [Qemu-devel] " Shannon Zhao
2018-06-12  1:36 ` Shannon Zhao
2018-06-12  1:36   ` Shannon Zhao
2018-06-12  1:36   ` [Qemu-devel] " Shannon Zhao
2018-06-12 12:17 ` Paolo Bonzini
2018-06-12 12:17   ` [Qemu-devel] " Paolo Bonzini
2018-06-13  2:15   ` Shannon Zhao
2018-06-13  2:15     ` Shannon Zhao
2018-06-13  2:15     ` [Qemu-devel] " Shannon Zhao
2018-06-13 15:58     ` Paolo Bonzini [this message]
2018-06-13 15:58       ` Paolo Bonzini

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