linux-kernel - Re: [PATCH 2/9] KVM: arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST

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Date:   Wed, 13 Jan 2021 18:18:20 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Alexandru Elisei <alexandru.elisei@....com>,
        eric.auger.pro@...il.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvmarm@...ts.cs.columbia.edu, maz@...nel.org,
        drjones@...hat.com
Cc:     james.morse@....com, julien.thierry.kdev@...il.com,
        suzuki.poulose@....com, shuah@...nel.org, pbonzini@...hat.com
Subject: Re: [PATCH 2/9] KVM: arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION
 read

Hi Alexandru,

On 1/6/21 6:12 PM, Alexandru Elisei wrote:
> Hi Eric,
> 
> The patch looks correct to me. kvm_vgic_addr() masks out all the bits except index
> from addr, so we don't need to do it in vgic_get_common_attr():
> 
> Reviewed-by: Alexandru Elisei <alexandru.elisei@....com>
> 
> One nitpick below.
> 
> On 12/12/20 6:50 PM, Eric Auger wrote:
>> The doc says:
>> "The characteristics of a specific redistributor region can
>>  be read by presetting the index field in the attr data.
>>  Only valid for KVM_DEV_TYPE_ARM_VGIC_V3"
>>
>> Unfortunately the existing code fails to read the input attr data
>> and thus the index always is 0.
> 
> addr is allocated on the stack, I don't think it will always be 0.
I removed this statement in the commit message. Thanks!

Eric
> 
> Thanks,
> Alex
>>
>> Fixes: 04c110932225 ("KVM: arm/arm64: Implement KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION")
>> Cc: stable@...r.kernel.org#v4.17+
>> Signed-off-by: Eric Auger <eric.auger@...hat.com>
>> ---
>>  arch/arm64/kvm/vgic/vgic-kvm-device.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c
>> index 44419679f91a..2f66cf247282 100644
>> --- a/arch/arm64/kvm/vgic/vgic-kvm-device.c
>> +++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c
>> @@ -226,6 +226,9 @@ static int vgic_get_common_attr(struct kvm_device *dev,
>>  		u64 addr;
>>  		unsigned long type = (unsigned long)attr->attr;
>>  
>> +		if (copy_from_user(&addr, uaddr, sizeof(addr)))
>> +			return -EFAULT;
>> +
>>  		r = kvm_vgic_addr(dev->kvm, type, &addr, false);
>>  		if (r)
>>  			return (r == -ENODEV) ? -ENXIO : r;
>