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

From: [email-masked] (Eric Auger)
Date: Tue, 10 May 2016 15:49:40 +0200

On 05/10/2016 03:42 PM, Marc Zyngier wrote:
> On 10/05/16 14:30, Christoffer Dall wrote:
>> On Fri, May 06, 2016 at 11:45:31AM +0100, 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) {
>>> +			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);
>>> +
>>
>> why do we need to do this?  I cannot find any consumers of this info
>> after we've left the hyp code.
> 
> I believe that's for vhost and irqfd. Or am I misreading your question?
Yes that's for irqfd. It triggers the resamplerfd which then "VFIO
unmasks" the IRQ

Eric
> 
>> Also, I think I offered a comment about why we would potentially need
>> this in the first place.  This is the famous race where hardware doesn't
>> guarantee consistency between the MISR and ELRSR right?
> 
> That's the one (except it is between EISR and ELRSR). I don't have your
> initial comment at hand, but would something like the following do?
> 
> 			/*
> 			 * The maintenance interrupt may not have had a
> 			 * chance to update ELRSR, so let's mark the LRs
> 			 * presents in EISR as empty.
> 			 */
>>
>>> +			cpuif->vgic_elrsr |= 1ULL << lr;
>>> +		}
>>> +	}
> 
> Thanks,
> 
> 	M.
>