Re: [PATCH v3 5/8] KVM: arm: vgic: Support 64-bit data manipulation on 32-bit host systems

[Vladimir Murzin <vladimir.murzin@arm.com>]

On 09/09/16 17:55, Marc Zyngier wrote:
> On 08/09/16 17:06, Vladimir Murzin wrote:
>> We have couple of 64-bit registers defined in GICv3 architecture, so
>> unsigned long accesses to these registers will only access a single
>> 32-bit part of that regitser. On the other hand these registers can't
>> be accessed as 64-bit with a single instruction like ldrd/strd or
>> ldmia/stmia if we run a 32-bit host because KVM does not support
>> access to MMIO space done by these instructions.
>>
>> It means that a 32-bit guest accesses these registers in 32-bit
>> chunks, so the only thing we need to do is to ensure that
>> extract_bytes() always takes 64-bit data.
>>
>> Since we are here fix couple of other width related issues catched by
>> gcc
>>
>> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
>> ---
>>  virt/kvm/arm/vgic/vgic-mmio-v3.c |    6 +++---
>>  virt/kvm/arm/vgic/vgic-mmio.h    |    2 +-
>>  2 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c
>> index acbe691..0d3c76a 100644
>> --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c
>> +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c
>> @@ -23,7 +23,7 @@
>>  #include "vgic-mmio.h"
>>  
>>  /* extract @num bytes at @offset bytes offset in data */
>> -unsigned long extract_bytes(unsigned long data, unsigned int offset,
>> +unsigned long extract_bytes(u64 data, unsigned int offset,
>>  			    unsigned int num)
>>  {
>>  	return (data >> (offset * 8)) & GENMASK_ULL(num * 8 - 1, 0);
>> @@ -181,7 +181,7 @@ static unsigned long vgic_mmio_read_v3r_typer(struct kvm_vcpu *vcpu,
>>  	int target_vcpu_id = vcpu->vcpu_id;
>>  	u64 value;
>>  
>> -	value = (mpidr & GENMASK(23, 0)) << 32;
>> +	value = (u64)(mpidr & GENMASK(23, 0)) << 32;
>>  	value |= ((target_vcpu_id & 0xffff) << 8);
>>  	if (target_vcpu_id == atomic_read(&vcpu->kvm->online_vcpus) - 1)
>>  		value |= GICR_TYPER_LAST;
>> @@ -611,7 +611,7 @@ void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg)
>>  	bool broadcast;
>>  
>>  	sgi = (reg & ICC_SGI1R_SGI_ID_MASK) >> ICC_SGI1R_SGI_ID_SHIFT;
>> -	broadcast = reg & BIT(ICC_SGI1R_IRQ_ROUTING_MODE_BIT);
>> +	broadcast = reg & BIT_ULL(ICC_SGI1R_IRQ_ROUTING_MODE_BIT);
>>  	target_cpus = (reg & ICC_SGI1R_TARGET_LIST_MASK) >> ICC_SGI1R_TARGET_LIST_SHIFT;
>>  	mpidr = SGI_AFFINITY_LEVEL(reg, 3);
>>  	mpidr |= SGI_AFFINITY_LEVEL(reg, 2);
>> diff --git a/virt/kvm/arm/vgic/vgic-mmio.h b/virt/kvm/arm/vgic/vgic-mmio.h
>> index 0b3ecf9..80f92ce 100644
>> --- a/virt/kvm/arm/vgic/vgic-mmio.h
>> +++ b/virt/kvm/arm/vgic/vgic-mmio.h
>> @@ -96,7 +96,7 @@ unsigned long vgic_data_mmio_bus_to_host(const void *val, unsigned int len);
>>  void vgic_data_host_to_mmio_bus(void *buf, unsigned int len,
>>  				unsigned long data);
>>  
>> -unsigned long extract_bytes(unsigned long data, unsigned int offset,
>> +unsigned long extract_bytes(u64 data, unsigned int offset,
>>  			    unsigned int num);
>>  
>>  u64 update_64bit_reg(u64 reg, unsigned int offset, unsigned int len,
>>
> 
> My personal preference would be to split this in two patches. One that
> changes extract_bytes to work on 64bit quantities, and another one that
> addresses the 64bit issues. Not a big deal though.
> 

Anyway I have to resend, so I'll split it per your preference ;)

> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> 

Thanks!

Vladimir

> Thanks,
> 
> 	M.
>