Subject: [PATCH v3 18/55] KVM: arm/arm64: vgic-new: Add GICv2 world switch backend

From: [email-masked] (Andre Przywara)
Date: Wed, 11 May 2016 14:09:26 +0100

Hi,

On 11/05/16 12:38, Eric Auger wrote:
> On 05/11/2016 01:30 PM, Andre Przywara wrote:
>> Hi,
>>
>> On 10/05/16 15:10, Eric Auger wrote:
>>> On 05/06/2016 12:45 PM, Andre Przywara wrote:
>>>> From: Marc Zyngier <[email-masked]>
>>>>
>>>> Processing maintenance interrupts and accessing the list registers
>>>> are dependent on the host's GIC version.
>>>> Introduce vgic-v2.c to contain GICv2 specific functions.
>>>> Implement the GICv2 specific code for syncing the emulation state
>>>> into the VGIC registers.
>>>>
>>>> Signed-off-by: Marc Zyngier <[email-masked]>
>>>> Signed-off-by: Christoffer Dall <[email-masked]>
>>>> Signed-off-by: Eric Auger <[email-masked]>
>>>> Signed-off-by: Andre Przywara <[email-masked]>
>>>> ---
>>>> Changelog RFC..v1:
>>>> - remove explicit LR_STATE clearing on maintenance interrupt handling
>>>> - improve documentation for vgic_v2_populate_lr()
>>>> - remove WARN_ON on non-edge IRQs in maintenance interrupts
>>>> - simplify multi-CPU source SGI handling
>>>>
>>>> Changelog v1 .. v2:
>>>> - inject the IRQ priority into the list register
>>>>
>>>> Changelog v2 .. v3:
>>>> - cleanup diff containing rebase artifacts
>>>>
>>>>  include/linux/irqchip/arm-gic.h |   1 +
>>>>  virt/kvm/arm/vgic/vgic-v2.c     | 178 ++++++++++++++++++++++++++++++++++++++++
>>>>  virt/kvm/arm/vgic/vgic.c        |   6 ++
>>>>  virt/kvm/arm/vgic/vgic.h        |   6 ++
>>>>  4 files changed, 191 insertions(+)
>>>>  create mode 100644 virt/kvm/arm/vgic/vgic-v2.c
>>>>
>>>> diff --git a/include/linux/irqchip/arm-gic.h b/include/linux/irqchip/arm-gic.h
>>>> index 9c94026..be0d26f 100644
>>>> --- a/include/linux/irqchip/arm-gic.h
>>>> +++ b/include/linux/irqchip/arm-gic.h
>>>> @@ -76,6 +76,7 @@
>>>>  #define GICH_LR_VIRTUALID		(0x3ff << 0)
>>>>  #define GICH_LR_PHYSID_CPUID_SHIFT	(10)
>>>>  #define GICH_LR_PHYSID_CPUID		(0x3ff << GICH_LR_PHYSID_CPUID_SHIFT)
>>>> +#define GICH_LR_PRIORITY_SHIFT		23
>>>>  #define GICH_LR_STATE			(3 << 28)
>>>>  #define GICH_LR_PENDING_BIT		(1 << 28)
>>>>  #define GICH_LR_ACTIVE_BIT		(1 << 29)
>>>> diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c
>>>> new file mode 100644
>>>> index 0000000..4cee616
>>>> --- /dev/null
>>>> +++ b/virt/kvm/arm/vgic/vgic-v2.c
>>>> @@ -0,0 +1,178 @@
>>>> +/*
>>>> + * Copyright (C) 2015, 2016 ARM Ltd.
>>>> + *
>>>> + * This program is free software; you can redistribute it and/or modify
>>>> + * it under the terms of the GNU General Public License version 2 as
>>>> + * published by the Free Software Foundation.
>>>> + *
>>>> + * This program is distributed in the hope that it will be useful,
>>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>>> + * GNU General Public License for more details.
>>>> + *
>>>> + * You should have received a copy of the GNU General Public License
>>>> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>>>> + */
>>>> +
>>>> +#include <linux/irqchip/arm-gic.h>
>>>> +#include <linux/kvm.h>
>>>> +#include <linux/kvm_host.h>
>>>> +
>>>> +#include "vgic.h"
>>>> +
>>>> +/*
>>>> + * Call this function to convert a u64 value to an unsigned long * bitmask
>>>> + * in a way that works on both 32-bit and 64-bit LE and BE platforms.
>>>> + *
>>>> + * Warning: Calling this function may modify *val.
>>>> + */
>>>> +static unsigned long *u64_to_bitmask(u64 *val)
>>>> +{
>>>> +#if defined(CONFIG_CPU_BIG_ENDIAN) && BITS_PER_LONG == 32
>>>> +	*val = (*val >> 32) | (*val << 32);
>>>> +#endif
>>>> +	return (unsigned long *)val;
>>>> +}
>>>> +
>>>> +void vgic_v2_process_maintenance(struct kvm_vcpu *vcpu)
>>>> +{
>>>> +	struct vgic_v2_cpu_if *cpuif = &vcpu->arch.vgic_cpu.vgic_v2;
>>>> +
>>>> +	if (cpuif->vgic_misr & GICH_MISR_EOI) {
>>>> +		u64 eisr = cpuif->vgic_eisr;
>>>> +		unsigned long *eisr_bmap = u64_to_bitmask(&eisr);
>>>> +		int lr;
>>>> +
>>>> +		for_each_set_bit(lr, eisr_bmap, kvm_vgic_global_state.nr_lr) {
>>> Didn't we say we could use vcpu->arch.vgic_cpu.used_lrs here?
>>
>> Why would that be useful? Don't we just want to see those LRs that had a
>> maintenance interrupt received? I don't see the point if iterating over
>> the used LRs, where we need to check for this condition somehow manually?
>> Or what am I missing here?
> 
> Well I thought that there is no use inspecting bits corresponding to
> unused LRs, no?

Mmh, maybe I got something wrong here, but this bitmap is supposedly
having only one bit set most of the time, also it points us to every LR
that we need to take care of. So it will never set bits for unused LRs.
By iterating over every used LR on the other hand we would touch LRs
that don't need servicing in this function, also the WARN_ON had to go
then (as we may touch EOIed IRQs).

Do you agree?

Cheers,
Andre.

> 
> Cheers
> 
> Eric
>>
>>>> +			u32 intid = cpuif->vgic_lr[lr] & GICH_LR_VIRTUALID;
>>>> +
>>>> +			WARN_ON(cpuif->vgic_lr[lr] & GICH_LR_STATE);
>>>> +
>>>> +			kvm_notify_acked_irq(vcpu->kvm, 0,
>>>> +					     intid - VGIC_NR_PRIVATE_IRQS);
>>>> +
>>>> +			cpuif->vgic_elrsr |= 1ULL << lr;
>>
>> So are we good with removing this line (and the respective one in v3)?
>>
>> Cheers,
>> Andre.
>>
>>>> +		}
>>>> +	}
>>>> +
>>>> +	/* check and disable underflow maintenance IRQ */
>>> check?
>>>
>>> Besides
>>> Reviewed-by: Eric Auger <[email-masked]>
>>>
>>> Eric
>>>> +	cpuif->vgic_hcr &= ~GICH_HCR_UIE;
>>>> +
>>>> +	/*
>>>> +	 * In the next iterations of the vcpu loop, if we sync the
>>>> +	 * vgic state after flushing it, but before entering the guest
>>>> +	 * (this happens for pending signals and vmid rollovers), then
>>>> +	 * make sure we don't pick up any old maintenance interrupts
>>>> +	 * here.
>>>> +	 */
>>>> +	cpuif->vgic_eisr = 0;
>>>> +}
>>>> +
>>>> +void vgic_v2_set_underflow(struct kvm_vcpu *vcpu)
>>>> +{
>>>> +	struct vgic_v2_cpu_if *cpuif = &vcpu->arch.vgic_cpu.vgic_v2;
>>>> +
>>>> +	cpuif->vgic_hcr |= GICH_HCR_UIE;
>>>> +}
>>>> +
>>>> +/*
>>>> + * transfer the content of the LRs back into the corresponding ap_list:
>>>> + * - active bit is transferred as is
>>>> + * - pending bit is
>>>> + *   - transferred as is in case of edge sensitive IRQs
>>>> + *   - set to the line-level (resample time) for level sensitive IRQs
>>>> + */
>>>> +void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
>>>> +{
>>>> +	struct vgic_v2_cpu_if *cpuif = &vcpu->arch.vgic_cpu.vgic_v2;
>>>> +	int lr;
>>>> +
>>>> +	for (lr = 0; lr < vcpu->arch.vgic_cpu.used_lrs; lr++) {
>>>> +		u32 val = cpuif->vgic_lr[lr];
>>>> +		u32 intid = val & GICH_LR_VIRTUALID;
>>>> +		struct vgic_irq *irq;
>>>> +
>>>> +		irq = vgic_get_irq(vcpu->kvm, vcpu, intid);
>>>> +
>>>> +		spin_lock(&irq->irq_lock);
>>>> +
>>>> +		/* Always preserve the active bit */
>>>> +		irq->active = !!(val & GICH_LR_ACTIVE_BIT);
>>>> +
>>>> +		/* Edge is the only case where we preserve the pending bit */
>>>> +		if (irq->config == VGIC_CONFIG_EDGE &&
>>>> +		    (val & GICH_LR_PENDING_BIT)) {
>>>> +			irq->pending = true;
>>>> +
>>>> +			if (vgic_irq_is_sgi(intid)) {
>>>> +				u32 cpuid = val & GICH_LR_PHYSID_CPUID;
>>>> +
>>>> +				cpuid >>= GICH_LR_PHYSID_CPUID_SHIFT;
>>>> +				irq->source |= (1 << cpuid);
>>>> +			}
>>>> +		}
>>>> +
>>>> +		/* Clear soft pending state when level IRQs have been acked */
>>>> +		if (irq->config == VGIC_CONFIG_LEVEL &&
>>>> +		    !(val & GICH_LR_PENDING_BIT)) {
>>>> +			irq->soft_pending = false;
>>>> +			irq->pending = irq->line_level;
>>>> +		}
>>>> +
>>>> +		spin_unlock(&irq->irq_lock);
>>>> +	}
>>>> +}
>>>> +
>>>> +/*
>>>> + * Populates the particular LR with the state of a given IRQ:
>>>> + * - for an edge sensitive IRQ the pending state is cleared in struct vgic_irq
>>>> + * - for a level sensitive IRQ the pending state value is unchanged;
>>>> + *   it is dictated directly by the input level
>>>> + *
>>>> + * If @irq describes an SGI with multiple sources, we choose the
>>>> + * lowest-numbered source VCPU and clear that bit in the source bitmap.
>>>> + *
>>>> + * The irq_lock must be held by the caller.
>>>> + */
>>>> +void vgic_v2_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr)
>>>> +{
>>>> +	u32 val = irq->intid;
>>>> +
>>>> +	if (irq->pending) {
>>>> +		val |= GICH_LR_PENDING_BIT;
>>>> +
>>>> +		if (irq->config == VGIC_CONFIG_EDGE)
>>>> +			irq->pending = false;
>>>> +
>>>> +		if (vgic_irq_is_sgi(irq->intid)) {
>>>> +			u32 src = ffs(irq->source);
>>>> +
>>>> +			BUG_ON(!src);
>>>> +			val |= (src - 1) << GICH_LR_PHYSID_CPUID_SHIFT;
>>>> +			irq->source &= ~(1 << (src - 1));
>>>> +			if (irq->source)
>>>> +				irq->pending = true;
>>>> +		}
>>>> +	}
>>>> +
>>>> +	if (irq->active)
>>>> +		val |= GICH_LR_ACTIVE_BIT;
>>>> +
>>>> +	if (irq->hw) {
>>>> +		val |= GICH_LR_HW;
>>>> +		val |= irq->hwintid << GICH_LR_PHYSID_CPUID_SHIFT;
>>>> +	} else {
>>>> +		if (irq->config == VGIC_CONFIG_LEVEL)
>>>> +			val |= GICH_LR_EOI;
>>>> +	}
>>>> +
>>>> +	/* The GICv2 LR only holds five bits of priority. */
>>>> +	val |= (irq->priority >> 3) << GICH_LR_PRIORITY_SHIFT;
>>>> +
>>>> +	vcpu->arch.vgic_cpu.vgic_v2.vgic_lr[lr] = val;
>>>> +}
>>>> +
>>>> +void vgic_v2_clear_lr(struct kvm_vcpu *vcpu, int lr)
>>>> +{
>>>> +	vcpu->arch.vgic_cpu.vgic_v2.vgic_lr[lr] = 0;
>>>> +}
>>>> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
>>>> index c6f8b9b..68d885c 100644
>>>> --- a/virt/kvm/arm/vgic/vgic.c
>>>> +++ b/virt/kvm/arm/vgic/vgic.c
>>>> @@ -397,10 +397,12 @@ retry:
>>>>  
>>>>  static inline void vgic_process_maintenance_interrupt(struct kvm_vcpu *vcpu)
>>>>  {
>>>> +	vgic_v2_process_maintenance(vcpu);
>>>>  }
>>>>  
>>>>  static inline void vgic_fold_lr_state(struct kvm_vcpu *vcpu)
>>>>  {
>>>> +	vgic_v2_fold_lr_state(vcpu);
>>>>  }
>>>>  
>>>>  /* Requires the ap_list_lock and the irq_lock to be held. */
>>>> @@ -409,14 +411,18 @@ static inline void vgic_populate_lr(struct kvm_vcpu *vcpu,
>>>>  {
>>>>  	DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&vcpu->arch.vgic_cpu.ap_list_lock));
>>>>  	DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&irq->irq_lock));
>>>> +
>>>> +	vgic_v2_populate_lr(vcpu, irq, lr);
>>>>  }
>>>>  
>>>>  static inline void vgic_clear_lr(struct kvm_vcpu *vcpu, int lr)
>>>>  {
>>>> +	vgic_v2_clear_lr(vcpu, lr);
>>>>  }
>>>>  
>>>>  static inline void vgic_set_underflow(struct kvm_vcpu *vcpu)
>>>>  {
>>>> +	vgic_v2_set_underflow(vcpu);
>>>>  }
>>>>  
>>>>  static int compute_ap_list_depth(struct kvm_vcpu *vcpu)
>>>> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
>>>> index 29b96b9..0db490e 100644
>>>> --- a/virt/kvm/arm/vgic/vgic.h
>>>> +++ b/virt/kvm/arm/vgic/vgic.h
>>>> @@ -22,4 +22,10 @@ struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
>>>>  			      u32 intid);
>>>>  bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq);
>>>>  
>>>> +void vgic_v2_process_maintenance(struct kvm_vcpu *vcpu);
>>>> +void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu);
>>>> +void vgic_v2_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr);
>>>> +void vgic_v2_clear_lr(struct kvm_vcpu *vcpu, int lr);
>>>> +void vgic_v2_set_underflow(struct kvm_vcpu *vcpu);
>>>> +
>>>>  #endif
>>>>
>>>
>