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From: Julien Thierry <julien.thierry@arm.com>
To: Marc Zyngier <marc.zyngier@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Cc: "Raslan, KarimAllah" <karahmed@amazon.de>,
	"Saidi, Ali" <alisaidi@amazon.com>
Subject: Re: [PATCH v2 1/9] KVM: arm/arm64: vgic: Add LPI translation cache definition
Date: Wed, 12 Jun 2019 09:49:53 +0100
Message-ID: <37a7411c-e7e0-e601-b88b-c12e8ebf9861@arm.com> (raw)
In-Reply-To: <54c8547a-51fb-8ae5-975f-261d3934221a@arm.com>



On 12/06/2019 09:16, Julien Thierry wrote:
> Hi Marc,
> 
> On 11/06/2019 18:03, Marc Zyngier wrote:

[...]

>> +
>> +void vgic_lpi_translation_cache_init(struct kvm *kvm)
>> +{
>> +	struct vgic_dist *dist = &kvm->arch.vgic;
>> +	unsigned int sz;
>> +	int i;
>> +
>> +	if (!list_empty(&dist->lpi_translation_cache))
>> +		return;
>> +
>> +	sz = atomic_read(&kvm->online_vcpus) * LPI_DEFAULT_PCPU_CACHE_SIZE;
>> +
>> +	for (i = 0; i < sz; i++) {
>> +		struct vgic_translation_cache_entry *cte;
>> +
>> +		/* An allocation failure is not fatal */
>> +		cte = kzalloc(sizeof(*cte), GFP_KERNEL);
>> +		if (WARN_ON(!cte))
>> +			break;
>> +
>> +		INIT_LIST_HEAD(&cte->entry);
>> +		list_add(&cte->entry, &dist->lpi_translation_cache);
> 
> Going through the series, it looks like this list is either empty
> (before the cache init) or has a fixed number
> (LPI_DEFAULT_PCPU_CACHE_SIZE * nr_cpus) of entries. And the list never
> grows nor shrinks throughout the series, so it seems odd to be using a
> list here.
> 
> Is there a reason for not using a dynamically allocated array instead of
> the list? (does list_move() provide a big perf advantage over swapping
> the data from one array entry to another? Or is there some other
> facility I am missing?
> 

Scratch that, I realized having the list makes it easier to implement
the LRU policy later in the series.

-- 
Julien Thierry
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  reply index

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-11 17:03 [PATCH v2 0/9] KVM: arm/arm64: vgic: ITS translation cache Marc Zyngier
2019-06-11 17:03 ` [PATCH v2 1/9] KVM: arm/arm64: vgic: Add LPI translation cache definition Marc Zyngier
2019-06-12  8:16   ` Julien Thierry
2019-06-12  8:49     ` Julien Thierry [this message]
2019-06-12  9:52     ` Marc Zyngier
2019-06-12 10:58       ` Julien Thierry
2019-06-12 12:28         ` Julien Thierry
2019-07-23 12:43   ` Auger Eric
2019-06-11 17:03 ` [PATCH v2 2/9] KVM: arm/arm64: vgic: Add __vgic_put_lpi_locked primitive Marc Zyngier
2019-06-11 17:03 ` [PATCH v2 3/9] KVM: arm/arm64: vgic-its: Add MSI-LPI translation cache invalidation Marc Zyngier
2019-07-23 12:39   ` Auger Eric
2019-06-11 17:03 ` [PATCH v2 4/9] KVM: arm/arm64: vgic-its: Invalidate MSI-LPI translation cache on specific commands Marc Zyngier
2019-07-01 12:38   ` Auger Eric
2019-07-22 10:54     ` Marc Zyngier
2019-07-23 12:25       ` Auger Eric
2019-07-23 12:43         ` Marc Zyngier
2019-07-23 12:47           ` Auger Eric
2019-07-23 12:50             ` Marc Zyngier
2019-06-11 17:03 ` [PATCH v2 5/9] KVM: arm/arm64: vgic-its: Invalidate MSI-LPI translation cache on disabling LPIs Marc Zyngier
2019-07-23 15:09   ` Auger Eric
2019-06-11 17:03 ` [PATCH v2 6/9] KVM: arm/arm64: vgic-its: Invalidate MSI-LPI translation cache on vgic teardown Marc Zyngier
2019-07-23 15:10   ` Auger Eric
2019-06-11 17:03 ` [PATCH v2 7/9] KVM: arm/arm64: vgic-its: Cache successful MSI->LPI translation Marc Zyngier
2019-06-25 11:50   ` Zenghui Yu
2019-06-25 12:31     ` Marc Zyngier
2019-06-25 16:00       ` Zenghui Yu
2019-06-26  3:54         ` Zenghui Yu
2019-06-26  7:55         ` Marc Zyngier
2019-07-23 15:21   ` Auger Eric
2019-06-11 17:03 ` [PATCH v2 8/9] KVM: arm/arm64: vgic-its: Check the LPI translation cache on MSI injection Marc Zyngier
2019-07-23 15:10   ` Auger Eric
2019-07-23 15:45     ` Marc Zyngier
2019-07-24  7:41       ` Auger Eric
2019-06-11 17:03 ` [PATCH v2 9/9] KVM: arm/arm64: vgic-irqfd: Implement kvm_arch_set_irq_inatomic Marc Zyngier
2019-07-23 15:14   ` Auger Eric
2019-07-25  8:24     ` Marc Zyngier
2019-07-23 11:14 ` [PATCH v2 0/9] KVM: arm/arm64: vgic: ITS translation cache Andre Przywara
2019-07-25  8:50   ` Marc Zyngier
2019-07-25 10:01     ` Andre Przywara
2019-07-25 15:37       ` Marc Zyngier

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