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 12:30:36 +0100

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?

>> +			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
>>
>