Re: [PATCH v2 9/9] KVM: arm/arm64: vgic-irqfd: Implement kvm_arch_set_irq_inatomic

From: Marc Zyngier <marc.zyngier@arm.com>
To: Auger Eric <eric.auger@redhat.com>,
	linux-arm-kernel@lists.infradead.org,
	 kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>,
	"Raslan, KarimAllah" <karahmed@amazon.de>,
	Julien Thierry <julien.thierry@arm.com>,
	Christoffer Dall <christoffer.dall@arm.com>,
	James Morse <james.morse@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>,
	"Saidi, Ali" <alisaidi@amazon.com>
Subject: Re: [PATCH v2 9/9] KVM: arm/arm64: vgic-irqfd: Implement kvm_arch_set_irq_inatomic
Date: Thu, 25 Jul 2019 09:24:38 +0100	[thread overview]
Message-ID: <24382fce-e165-4e79-1703-d019efcdf6e8@arm.com> (raw)
In-Reply-To: <a63b08b8-9539-09b4-1060-7c0d2f2eacac@redhat.com>

On 23/07/2019 16:14, Auger Eric wrote:
> Hi Marc,
> 
> On 6/11/19 7:03 PM, Marc Zyngier wrote:
>> Now that we have a cache of MSI->LPI translations, it is pretty
>> easy to implement kvm_arch_set_irq_inatomic (this cache can be
>> parsed without sleeping).
>>
>> Hopefully, this will improve some LPI-heavy workloads.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>>  virt/kvm/arm/vgic/vgic-irqfd.c | 36 ++++++++++++++++++++++++++++------
>>  1 file changed, 30 insertions(+), 6 deletions(-)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-irqfd.c b/virt/kvm/arm/vgic/vgic-irqfd.c
>> index 99e026d2dade..9f203ed8c8f3 100644
>> --- a/virt/kvm/arm/vgic/vgic-irqfd.c
>> +++ b/virt/kvm/arm/vgic/vgic-irqfd.c
>> @@ -77,6 +77,15 @@ int kvm_set_routing_entry(struct kvm *kvm,
>>  	return r;
>>  }
>>  
>> +static void kvm_populate_msi(struct kvm_kernel_irq_routing_entry *e,
>> +			     struct kvm_msi *msi)
>> +{
>> +	msi->address_lo = e->msi.address_lo;
>> +	msi->address_hi = e->msi.address_hi;
>> +	msi->data = e->msi.data;
>> +	msi->flags = e->msi.flags;
>> +	msi->devid = e->msi.devid;
>> +}
>>  /**
>>   * kvm_set_msi: inject the MSI corresponding to the
> s/:/ -
>>   * MSI routing entry
>> @@ -90,21 +99,36 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
>>  {
>>  	struct kvm_msi msi;
>>  
>> -	msi.address_lo = e->msi.address_lo;
>> -	msi.address_hi = e->msi.address_hi;
>> -	msi.data = e->msi.data;
>> -	msi.flags = e->msi.flags;
>> -	msi.devid = e->msi.devid;
>> -
>>  	if (!vgic_has_its(kvm))
>>  		return -ENODEV;
>>  
>>  	if (!level)
>>  		return -1;
>>  
>> +	kvm_populate_msi(e, &msi);
>>  	return vgic_its_inject_msi(kvm, &msi);
>>  }
>>  
>> +/**
>> + * kvm_arch_set_irq_inatomic: fast-path for irqfd injection
> s/:/ -
>> + *
>> + * Currently only direct MSI injecton is supported.
> injection
>> + */
>> +int kvm_arch_set_irq_inatomic(struct kvm_kernel_irq_routing_entry *e,
>> +			      struct kvm *kvm, int irq_source_id, int level,
>> +			      bool line_status)
>> +{
>> +	if (e->type == KVM_IRQ_ROUTING_MSI && vgic_has_its(kvm) && level) {
>> +		struct kvm_msi msi;
>> +
>> +		kvm_populate_msi(e, &msi);
>> +		if (!vgic_its_inject_cached_translation(kvm, &msi))
>> +			return 0;
> if this fails since its->enabled is false we will re-attempt the
> injection though the normal injection path but that's not a big deal.

Yeah, I wouldn't worry about that. If there is a screaming device, so be
it. The guest should know better...

>> +	}
>> +
>> +	return -EWOULDBLOCK;
>> +}
>> +
>>  int kvm_vgic_setup_default_irq_routing(struct kvm *kvm)
>>  {
>>  	struct kvm_irq_routing_entry *entries;
>>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks Eric.

	M.
-- 
Jazz is not dead. It just smells funny...

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