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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH for-4.6 2/4] xen/arm: vgic: Keep track of vIRQ used by a domain
Hi Ian,
On 13/01/15 15:51, Ian Campbell wrote:
> On Fri, 2014-12-12 at 14:43 +0000, Julien Grall wrote:
>> While it's easy to know which hardware IRQ is assigned to a domain, there
>> is no way to know which IRQ is emulated by Xen for a specific domain.
>
> It seems you are tracking all valid interrupts, including hardware ones,
> not just those for emulated devices? Perhaps rather than emulated you
> meant "allocated to the guest" or "routed" or something?
>
>> Introduce a bitmap to keep track of every vIRQ used by a domain. This
>> will be used later to find free vIRQ for interrupt device assignment and
>> emulated interrupt.
>
> Actually, don't you implement the alloc/free of vIRQs here too?
Yes.
> Is there a usecase for tracking SPIs in this way, or would tracking PPIs
> only be sufficient?
We need to track everything for interrupt assignment to a guest/dom0. So
if the guest ask for a free vIRQ we can give it directly.
>> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
>> ---
>> xen/arch/arm/domain_build.c | 6 +++
>> xen/arch/arm/platforms/xgene-storm.c | 4 ++
>> xen/arch/arm/vgic.c | 76
>> ++++++++++++++++++++++++++++++++++++
>> xen/arch/arm/vtimer.c | 15 +++++++
>> xen/include/asm-arm/domain.h | 1 +
>> xen/include/asm-arm/vgic.h | 13 ++++++
>> 6 files changed, 115 insertions(+)
>>
>> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
>> index de180d8..c238c8f 100644
>> --- a/xen/arch/arm/domain_build.c
>> +++ b/xen/arch/arm/domain_build.c
>> @@ -968,6 +968,12 @@ static int map_device(struct domain *d, struct
>> dt_device_node *dev)
>> irq = res;
>>
>> DPRINT("irq %u = %u\n", i, irq);
>> + /*
>> + * Checking the return of vgic_reserve_virq is not
>> + * necessary. It should not fail except when we try to map
>> + * twice the IRQ. This can happen if the IRQ is shared
>
> Return and handle EBUSY to distinguish other errors?
vgic_reserve_virq can fail for 2 reasons:
- The IRQ is too high to handle by the vGIC => Unlikely as DOM0 use the
same IRQ number as the hardware.
- The vIRQ is already reserved.
The former will be catch just after with route_irq_to_guest. So I don't
think it's worth to change the return from a bool to an int and return
-EBUSY.
> ("try to map the IRQ twice")
>
>> + */
>> + vgic_reserve_virq(d, irq);
>> res = route_irq_to_guest(d, irq, dt_node_name(dev));
>> if ( res )
>> {
>> diff --git a/xen/arch/arm/platforms/xgene-storm.c
>> b/xen/arch/arm/platforms/xgene-storm.c
>> index 0b3492d..416d42c 100644
>> --- a/xen/arch/arm/platforms/xgene-storm.c
>> +++ b/xen/arch/arm/platforms/xgene-storm.c
>> @@ -71,6 +71,10 @@ static int map_one_spi(struct domain *d, const char *what,
>>
>> printk("Additional IRQ %u (%s)\n", irq, what);
>>
>> + if ( !vgic_reserve_virq(d, irq) )
>> + printk("Failed to reserve the vIRQ %u on dom%d\n",
>
> Drop "the".
Ok.
>> + irq, d->domain_id);
>> +
>> ret = route_irq_to_guest(d, irq, what);
>> if ( ret )
>> printk("Failed to route %s to dom%d\n", what, d->domain_id);
>> diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
>> index 75cb7ff..dbfc259 100644
>> --- a/xen/arch/arm/vgic.c
>> +++ b/xen/arch/arm/vgic.c
>> @@ -87,6 +87,8 @@ int domain_vgic_init(struct domain *d)
>> return -ENODEV;
>> }
>>
>> + spin_lock_init(&d->arch.vgic.lock);
>> +
>> d->arch.vgic.shared_irqs =
>> xzalloc_array(struct vgic_irq_rank, DOMAIN_NR_RANKS(d));
>> if ( d->arch.vgic.shared_irqs == NULL )
>> @@ -107,6 +109,15 @@ int domain_vgic_init(struct domain *d)
>>
>> d->arch.vgic.handler->domain_init(d);
>>
>> + d->arch.vgic.allocated_irqs =
>> + xzalloc_array(unsigned long, BITS_TO_LONGS(vgic_num_irqs(d)));
>
> (this was why I asked if tracking SPIs was needed...)
To complete my answer above:
- dom0: vgic_num_irqs() = number of hardware IRQS
- guest: vgic_num_irqs() = 32.
So we don't waste memory.
>
>> + if ( !d->arch.vgic.allocated_irqs )
>> + return -ENOMEM;
>> +
>> + /* vIRQ0-15 (SGIs) are reserved */
>> + for (i = 0; i <= 15; i++)
>> + set_bit(i, d->arch.vgic.allocated_irqs);
>> +
>> return 0;
>> }
>>
>> @@ -119,6 +130,7 @@ void domain_vgic_free(struct domain *d)
>> {
>> xfree(d->arch.vgic.shared_irqs);
>> xfree(d->arch.vgic.pending_irqs);
>> + xfree(d->arch.vgic.allocated_irqs);
>> }
>>
>> int vcpu_vgic_init(struct vcpu *v)
>> @@ -441,6 +453,70 @@ int vgic_emulate(struct cpu_user_regs *regs, union hsr
>> hsr)
>> return v->domain->arch.vgic.handler->emulate_sysreg(regs, hsr);
>> }
>>
>> +bool_t vgic_reserve_virq(struct domain *d, unsigned int virq)
>> +{
>> + bool_t reserved;
>> +
>> + if ( virq >= vgic_num_irqs(d) )
>> + return 0;
>
> EINVAL?
vgic_reserve_irq returns a boolean:
0 => not reserved
1 => reserved
I don't see why we should return an int in this case, as the caller
should know how to use it.
>> + spin_lock(&d->arch.vgic.lock);
>> + reserved = !test_and_set_bit(virq, d->arch.vgic.allocated_irqs);
>> + spin_unlock(&d->arch.vgic.lock);
>> +
>> + return reserved;
>> +}
>> +
>> +int vgic_allocate_virq(struct domain *d, bool_t spi)
>> +{
>> + int ret = -1;
>> + unsigned int virq;
>> +
>> + spin_lock(&d->arch.vgic.lock);
>> + if ( !spi )
>> + {
>> + virq = find_first_zero_bit(d->arch.vgic.allocated_irqs, 32);
>
> I think you could use find_next_zero_bit here to start the search at bit
> 16 and stop at bit 31. Having done so, it might be nicer to if (spi) to
> select min and max IRQs and have the bit manipulation all be common.
I will give a look for the next version.
>
>> +void vgic_free_virq(struct domain *d, unsigned int virq)
>
> It only frees spis, but the alloc version can do SPI or PPI. Is that on
> purpose?
I forgot to update vgic_free_virq when I made the support for PPIs.
>> +{
>> + unsigned int spi;
>> +
>> + if ( is_hardware_domain(d) )
>> + return;
>> +
>> + if ( virq < 32 && virq >= vgic_num_irqs(d) )
>> + return;
>> +
>> + spi = virq - 32;
>> +
>> + /* Taking the vGIC domain lock is not necessary. We don't care if
>> + * the bit is cleared a bit later. What only matters is bit to 1.
>
> I don't grok the last sentence here.
>
>> + *
>> + * With this solution vgic_allocate may fail to find an vIRQ if the
>> + * allocated_irqs is fully. But we don't care.
>
> are some words missing after fully?
This will be dropped in the next version. So forget this part :).
>> + */
>> + clear_bit(spi, d->arch.vgic.allocated_irqs);
>> +}
>> +
>> /*
>> * Local variables:
>> * mode: C
>> diff --git a/xen/arch/arm/vtimer.c b/xen/arch/arm/vtimer.c
>> index 2e95ceb..de660bb 100644
>> + */
>> +extern int vgic_allocate_virq(struct domain *d, bool_t spi);
>> +
>> +extern void vgic_free_virq(struct domain *d, unsigned int irq);
>> +
>> #endif /* __ASM_ARM_VGIC_H__ */
>>
>> /*
>
>
>> --- a/xen/arch/arm/vtimer.c
>> +++ b/xen/arch/arm/vtimer.c
>> @@ -49,6 +49,21 @@ int domain_vtimer_init(struct domain *d)
>> {
>> d->arch.phys_timer_base.offset = NOW();
>> d->arch.virt_timer_base.offset = READ_SYSREG64(CNTPCT_EL0);
>> +
>> + /* At this stage vgic_reserve_virq can't fail */
>> + if ( is_hardware_domain(d) )
>> + {
>> + BUG_ON(!vgic_reserve_virq(d, timer_get_irq(TIMER_PHYS_SECURE_PPI)));
>> + BUG_ON(!vgic_reserve_virq(d,
>> timer_get_irq(TIMER_PHYS_NONSECURE_PPI)));
>> + BUG_ON(!vgic_reserve_virq(d, timer_get_irq(TIMER_VIRT_PPI)));
>> + }
>> + else
>> + {
>> + BUG_ON(!vgic_reserve_virq(d, GUEST_TIMER_PHYS_S_PPI));
>> + BUG_ON(!vgic_reserve_virq(d, GUEST_TIMER_PHYS_NS_PPI));
>> + BUG_ON(!vgic_reserve_virq(d, GUEST_TIMER_VIRT_PPI));
>
> Although BUG_ON is not conditional on $debug I think we still should
> avoid side effects in the condition.
I know, but this should never fail as it called during on domain
construction. If so we may have some other issue later if we decide to
assign PPI to a guest.
I would prefer to keep the BUG_ON here.
>
>> diff --git a/xen/include/asm-arm/vgic.h b/xen/include/asm-arm/vgic.h
>> index 74d5a4e..9e167fa 100644
>> --- a/xen/include/asm-arm/vgic.h
>> +++ b/xen/include/asm-arm/vgic.h
>> @@ -199,6 +199,19 @@ extern int vgic_to_sgi(struct vcpu *v, register_t sgir,
>> enum gic_sgi_mode irqmode, int virq,
>> unsigned long vcpu_mask);
>> extern void vgic_migrate_irq(struct vcpu *old, struct vcpu *new, unsigned
>> int irq);
>> +
>> +/* Reserve a specific guest vIRQ */
>> +extern bool_t vgic_reserve_virq(struct domain *d, unsigned int virq);
>> +
>> +/*
>> + * Allocate a guest VIRQ
>> + * - spi == 0 => allocate a PPI. It will be the same on every vCPU
>> + * - spi == 0 => allocate an SGI
>
> s/== 0/== 1/ and s/SGI/SPI/ in the last line.
I will fix it.
Regards,
--
Julien Grall
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