Re: [PATCH 1/2] KVM: provide irq_unsafe kvm_guest_{enter|exit}

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From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: KVM <kvm@vger.kernel.org>,
	kvm-ppc@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-mips@linux-mips.org,
	Cornelia Huck <cornelia.huck@de.ibm.com>,
	Alexander Graf <agraf@suse.de>
Subject: Re: [PATCH 1/2] KVM: provide irq_unsafe kvm_guest_{enter|exit}
Date: Thu, 30 Apr 2015 12:07:38 +0000	[thread overview]
Message-ID: <55421B0A.2060606@de.ibm.com> (raw)
In-Reply-To: <554219F2.9020805@de.ibm.com>

Am 30.04.2015 um 14:02 schrieb Christian Borntraeger:
> Am 30.04.2015 um 14:01 schrieb Christian Borntraeger:
>> Am 30.04.2015 um 13:50 schrieb Paolo Bonzini:
>>>
>>>
>>> On 30/04/2015 13:43, Christian Borntraeger wrote:
>>>> +/* must be called with irqs disabled */
>>>> +static inline void __kvm_guest_enter(void)
>>>>  {
>>>> -	unsigned long flags;
>>>> -
>>>> -	BUG_ON(preemptible());
>>>
>>> Please keep the BUG_ON() in kvm_guest_enter.  Otherwise looks good, thanks!
> 
> Ah, you mean have the BUG_ON in the non underscore version? Yes, makes sense.

Hmmm, too quick.
the BUG_ON was there to make sure that rcu_virt_note_context_switch is safe.
The reworked code pulls the rcu_virt_note_context_switch within the irq_save
section so we no longer need this BUG_ON, no?

Christian

WARNING: multiple messages have this Message-ID (diff)

From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-mips@linux-mips.org, KVM <kvm@vger.kernel.org>,
	kvm-ppc@vger.kernel.org, Cornelia Huck <cornelia.huck@de.ibm.com>,
	kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH 1/2] KVM: provide irq_unsafe kvm_guest_{enter|exit}
Date: Thu, 30 Apr 2015 14:07:38 +0200	[thread overview]
Message-ID: <55421B0A.2060606@de.ibm.com> (raw)
In-Reply-To: <554219F2.9020805@de.ibm.com>

Am 30.04.2015 um 14:02 schrieb Christian Borntraeger:
> Am 30.04.2015 um 14:01 schrieb Christian Borntraeger:
>> Am 30.04.2015 um 13:50 schrieb Paolo Bonzini:
>>>
>>>
>>> On 30/04/2015 13:43, Christian Borntraeger wrote:
>>>> +/* must be called with irqs disabled */
>>>> +static inline void __kvm_guest_enter(void)
>>>>  {
>>>> -	unsigned long flags;
>>>> -
>>>> -	BUG_ON(preemptible());
>>>
>>> Please keep the BUG_ON() in kvm_guest_enter.  Otherwise looks good, thanks!
> 
> Ah, you mean have the BUG_ON in the non underscore version? Yes, makes sense.

Hmmm, too quick.
the BUG_ON was there to make sure that rcu_virt_note_context_switch is safe.
The reworked code pulls the rcu_virt_note_context_switch within the irq_save
section so we no longer need this BUG_ON, no?

Christian

WARNING: multiple messages have this Message-ID (diff)

From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: KVM <kvm@vger.kernel.org>,
	kvm-ppc@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-mips@linux-mips.org,
	Cornelia Huck <cornelia.huck@de.ibm.com>,
	Alexander Graf <agraf@suse.de>
Subject: Re: [PATCH 1/2] KVM: provide irq_unsafe kvm_guest_{enter|exit}
Date: Thu, 30 Apr 2015 14:07:38 +0200	[thread overview]
Message-ID: <55421B0A.2060606@de.ibm.com> (raw)
In-Reply-To: <554219F2.9020805@de.ibm.com>

Am 30.04.2015 um 14:02 schrieb Christian Borntraeger:
> Am 30.04.2015 um 14:01 schrieb Christian Borntraeger:
>> Am 30.04.2015 um 13:50 schrieb Paolo Bonzini:
>>>
>>>
>>> On 30/04/2015 13:43, Christian Borntraeger wrote:
>>>> +/* must be called with irqs disabled */
>>>> +static inline void __kvm_guest_enter(void)
>>>>  {
>>>> -	unsigned long flags;
>>>> -
>>>> -	BUG_ON(preemptible());
>>>
>>> Please keep the BUG_ON() in kvm_guest_enter.  Otherwise looks good, thanks!
> 
> Ah, you mean have the BUG_ON in the non underscore version? Yes, makes sense.

Hmmm, too quick.
the BUG_ON was there to make sure that rcu_virt_note_context_switch is safe.
The reworked code pulls the rcu_virt_note_context_switch within the irq_save
section so we no longer need this BUG_ON, no?

Christian

next prev parent reply	other threads:[~2015-04-30 12:07 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-30 11:43 [PATCHv2 0/2] KVM: micro-optimization and interrupt disabling Christian Borntraeger
2015-04-30 11:43 ` Christian Borntraeger
2015-04-30 11:43 ` Christian Borntraeger
2015-04-30 11:43 ` [PATCH 1/2] KVM: provide irq_unsafe kvm_guest_{enter|exit} Christian Borntraeger
2015-04-30 11:43   ` Christian Borntraeger
2015-04-30 11:50   ` Paolo Bonzini
2015-04-30 11:50     ` Paolo Bonzini
2015-04-30 12:01     ` Christian Borntraeger
2015-04-30 12:01       ` Christian Borntraeger
2015-04-30 12:02       ` Christian Borntraeger
2015-04-30 12:02         ` Christian Borntraeger
2015-04-30 12:07         ` Christian Borntraeger [this message]
2015-04-30 12:07           ` Christian Borntraeger
2015-04-30 12:07           ` Christian Borntraeger
2015-04-30 12:28           ` Paolo Bonzini
2015-04-30 12:28             ` Paolo Bonzini
2015-04-30 12:28             ` Paolo Bonzini
2015-04-30 11:43 ` [PATCH 2/2] KVM: arm/mips/x86/power use __kvm_guest_{enter|exit} Christian Borntraeger
2015-04-30 11:43   ` Christian Borntraeger
2015-05-05 12:08   ` Christoffer Dall
2015-05-05 12:08     ` Christoffer Dall

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