linux-kernel - Re: [PATCH 0/3] KVM: Make kvm

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Message-ID: <523EAFFA.6060203@redhat.com>
Date:	Sun, 22 Sep 2013 10:53:14 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	linux-kernel@...r.kernel.org,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	kvm@...r.kernel.org, jan.kiszka@...mens.com
Subject: Re: [PATCH 0/3] KVM: Make kvm_lock non-raw

Il 22/09/2013 09:42, Gleb Natapov ha scritto:
> On Mon, Sep 16, 2013 at 04:06:10PM +0200, Paolo Bonzini wrote:
>> Paul Gortmaker reported a BUG on preempt-rt kernels, due to taking the
>> mmu_lock within the raw kvm_lock in mmu_shrink_scan.  He provided a
>> patch that shrunk the kvm_lock critical section so that the mmu_lock
>> critical section does not nest with it, but in the end there is no reason
>> for the vm_list to be protected by a raw spinlock.  Only manipulations
>> of kvm_usage_count and the consequent hardware_enable/disable operations
>> are not preemptable.
>>
>> This small series thus splits the kvm_lock in the "raw" part and the
>> "non-raw" part.
>>
>> Paul, could you please provide your Tested-by?
>>
> Reviewed-by: Gleb Natapov <gleb@...hat.com>
> 
> But why should it go to stable?

It is a regression from before the kvm_lock was made raw.  Secondarily,
it takes a much longer time before a patch hits -rt trees (can even be
as much as a year) and this patch does nothing on non-rt trees.  So
without putting it into stable it would get no actual coverage.

Paolo
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