linux-kernel - Re: [PATCH v2 02/10] KVM: arm/arm64: vgic-its: Always allow clearing GITS

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Date:   Fri, 6 Oct 2017 17:29:02 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Andre Przywara <andre.przywara@....com>, eric.auger.pro@...il.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        marc.zyngier@....com, cdall@...aro.org, peter.maydell@...aro.org,
        wanghaibin.wang@...wei.com
Cc:     wu.wubin@...wei.com
Subject: Re: [PATCH v2 02/10] KVM: arm/arm64: vgic-its: Always allow clearing
 GITS_CREADR/CWRITER

Hi,

On 06/10/2017 16:37, Andre Przywara wrote:
> Hi,
> 
> On 27/09/17 14:28, Eric Auger wrote:
>> If the GITS_CBASER Size field is 0, which can correspond to a
>> reset value, the userspace fails to set the GITS_CREADR/CWRITER
>> offsets to 0. This failure is not justified.
>>
>> Let's allow this setting which can also correspond to a reset value.
> 
> But the GITS_CBASER size field has a +1 encoding, so can never be 0, if
> I understand the manual (and ITS_CMD_BUFFER_SIZE) correctly.
Oh OK, you're. I missed that. I would have sworn I've seen that failure
but I must have misinterpreted it.

Thanks!

Eric
> 
> What am I missing here?
> 
> Cheers,
> Andre.
> 
>> Signed-off-by: Eric Auger <eric.auger@...hat.com>
>>
>> ---
>>
>> need to CC stable
>> ---
>>  virt/kvm/arm/vgic/vgic-its.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
>> index fbbc97b..76bed2d 100644
>> --- a/virt/kvm/arm/vgic/vgic-its.c
>> +++ b/virt/kvm/arm/vgic/vgic-its.c
>> @@ -1329,7 +1329,7 @@ static void vgic_mmio_write_its_cwriter(struct kvm *kvm, struct vgic_its *its,
>>  
>>  	reg = update_64bit_reg(its->cwriter, addr & 7, len, val);
>>  	reg = ITS_CMD_OFFSET(reg);
>> -	if (reg >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
>> +	if (reg && reg >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
>>  		mutex_unlock(&its->cmd_lock);
>>  		return;
>>  	}
>> @@ -1370,7 +1370,7 @@ static int vgic_mmio_uaccess_write_its_creadr(struct kvm *kvm,
>>  	}
>>  
>>  	cmd_offset = ITS_CMD_OFFSET(val);
>> -	if (cmd_offset >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
>> +	if (cmd_offset && cmd_offset >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
>>  		ret = -EINVAL;
>>  		goto out;
>>  	}
>>