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From: Marc Zyngier <maz@kernel.org>
To: Eric Auger <eric.auger@redhat.com>
Cc: kvm@vger.kernel.org, shuah@kernel.org,
	linux-kernel@vger.kernel.org, pbonzini@redhat.com,
	kvmarm@lists.cs.columbia.edu, eric.auger.pro@gmail.com
Subject: Re: [PATCH v4 1/8] KVM: arm64: vgic-v3: Fix some error codes when setting RDIST base
Date: Thu, 01 Apr 2021 11:52:15 +0100	[thread overview]
Message-ID: <87wntmp99c.wl-maz@kernel.org> (raw)
In-Reply-To: <20210401085238.477270-2-eric.auger@redhat.com>

Hi Eric,

On Thu, 01 Apr 2021 09:52:31 +0100,
Eric Auger <eric.auger@redhat.com> wrote:
> 
> KVM_DEV_ARM_VGIC_GRP_ADDR group doc says we should return
> -EEXIST in case the base address of the redist is already set.
> We currently return -EINVAL.
> 
> However we need to return -EINVAL in case a legacy REDIST address
> is attempted to be set while REDIST_REGIONS were set. This case
> is discriminated by looking at the count field.
> 
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> 
> ---
> 
> v1 -> v2:
> - simplify the check sequence
> ---
>  arch/arm64/kvm/vgic/vgic-mmio-v3.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> index 15a6c98ee92f0..013b737b658f8 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> @@ -791,10 +791,6 @@ static int vgic_v3_insert_redist_region(struct kvm *kvm, uint32_t index,
>  	size_t size = count * KVM_VGIC_V3_REDIST_SIZE;
>  	int ret;
>  
> -	/* single rdist region already set ?*/
> -	if (!count && !list_empty(rd_regions))
> -		return -EINVAL;
> -
>  	/* cross the end of memory ? */
>  	if (base + size < base)
>  		return -EINVAL;
> @@ -805,11 +801,14 @@ static int vgic_v3_insert_redist_region(struct kvm *kvm, uint32_t index,
>  	} else {
>  		rdreg = list_last_entry(rd_regions,
>  					struct vgic_redist_region, list);
> -		if (index != rdreg->index + 1)
> -			return -EINVAL;
>  
> -		/* Cannot add an explicitly sized regions after legacy region */
> -		if (!rdreg->count)
> +		if ((!count) != (!rdreg->count))
> +			return -EINVAL; /* Mix REDIST and REDIST_REGION */

Urgh... The triple negation killed me. Can we come up with a more
intuitive expression? Something like:

		/* Don't mix single region and discrete redist regions */
		if (!count && rdreg->count)
			return -EINVAL;

Does it capture what you want to express?

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.
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WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Eric Auger <eric.auger@redhat.com>
Cc: eric.auger.pro@gmail.com, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	drjones@redhat.com, alexandru.elisei@arm.com,
	james.morse@arm.com, suzuki.poulose@arm.com, shuah@kernel.org,
	pbonzini@redhat.com
Subject: Re: [PATCH v4 1/8] KVM: arm64: vgic-v3: Fix some error codes when setting RDIST base
Date: Thu, 01 Apr 2021 11:52:15 +0100	[thread overview]
Message-ID: <87wntmp99c.wl-maz@kernel.org> (raw)
In-Reply-To: <20210401085238.477270-2-eric.auger@redhat.com>

Hi Eric,

On Thu, 01 Apr 2021 09:52:31 +0100,
Eric Auger <eric.auger@redhat.com> wrote:
> 
> KVM_DEV_ARM_VGIC_GRP_ADDR group doc says we should return
> -EEXIST in case the base address of the redist is already set.
> We currently return -EINVAL.
> 
> However we need to return -EINVAL in case a legacy REDIST address
> is attempted to be set while REDIST_REGIONS were set. This case
> is discriminated by looking at the count field.
> 
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> 
> ---
> 
> v1 -> v2:
> - simplify the check sequence
> ---
>  arch/arm64/kvm/vgic/vgic-mmio-v3.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> index 15a6c98ee92f0..013b737b658f8 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> @@ -791,10 +791,6 @@ static int vgic_v3_insert_redist_region(struct kvm *kvm, uint32_t index,
>  	size_t size = count * KVM_VGIC_V3_REDIST_SIZE;
>  	int ret;
>  
> -	/* single rdist region already set ?*/
> -	if (!count && !list_empty(rd_regions))
> -		return -EINVAL;
> -
>  	/* cross the end of memory ? */
>  	if (base + size < base)
>  		return -EINVAL;
> @@ -805,11 +801,14 @@ static int vgic_v3_insert_redist_region(struct kvm *kvm, uint32_t index,
>  	} else {
>  		rdreg = list_last_entry(rd_regions,
>  					struct vgic_redist_region, list);
> -		if (index != rdreg->index + 1)
> -			return -EINVAL;
>  
> -		/* Cannot add an explicitly sized regions after legacy region */
> -		if (!rdreg->count)
> +		if ((!count) != (!rdreg->count))
> +			return -EINVAL; /* Mix REDIST and REDIST_REGION */

Urgh... The triple negation killed me. Can we come up with a more
intuitive expression? Something like:

		/* Don't mix single region and discrete redist regions */
		if (!count && rdreg->count)
			return -EINVAL;

Does it capture what you want to express?

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

  reply	other threads:[~2021-04-01 10:52 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-01  8:52 [PATCH v4 0/8] KVM/ARM: Some vgic fixes and init sequence KVM selftests Eric Auger
2021-04-01  8:52 ` Eric Auger
2021-04-01  8:52 ` [PATCH v4 1/8] KVM: arm64: vgic-v3: Fix some error codes when setting RDIST base Eric Auger
2021-04-01  8:52   ` Eric Auger
2021-04-01 10:52   ` Marc Zyngier [this message]
2021-04-01 10:52     ` Marc Zyngier
2021-04-01 11:43     ` Auger Eric
2021-04-01 11:43       ` Auger Eric
2021-04-01  8:52 ` [PATCH v4 2/8] KVM: arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION read Eric Auger
2021-04-01  8:52   ` Eric Auger
2021-04-01  8:52 ` [PATCH v4 3/8] KVM: arm64: vgic-v3: Fix error handling in vgic_v3_set_redist_base() Eric Auger
2021-04-01  8:52   ` Eric Auger
2021-04-01  8:52 ` [PATCH v4 4/8] KVM: arm/arm64: vgic: Reset base address on kvm_vgic_dist_destroy() Eric Auger
2021-04-01  8:52   ` Eric Auger
2021-04-01  8:52 ` [PATCH v4 5/8] docs: kvm: devices/arm-vgic-v3: enhance KVM_DEV_ARM_VGIC_CTRL_INIT doc Eric Auger
2021-04-01  8:52   ` Eric Auger
2021-04-01  8:52 ` [PATCH v4 6/8] KVM: arm64: Simplify argument passing to vgic_uaccess_[read|write] Eric Auger
2021-04-01  8:52   ` Eric Auger
2021-04-01  8:52 ` [PATCH v4 7/8] KVM: arm64: vgic-v3: Expose GICR_TYPER.Last for userspace Eric Auger
2021-04-01  8:52   ` Eric Auger
2021-04-01 13:42   ` Marc Zyngier
2021-04-01 13:42     ` Marc Zyngier
2021-04-01 17:03     ` Auger Eric
2021-04-01 17:03       ` Auger Eric
2021-04-01 17:30       ` Marc Zyngier
2021-04-01 17:30         ` Marc Zyngier
2021-04-01 19:16         ` Auger Eric
2021-04-01 19:16           ` Auger Eric
2021-04-02  9:32           ` Marc Zyngier
2021-04-02  9:32             ` Marc Zyngier
2021-04-01  8:52 ` [PATCH v4 8/8] KVM: selftests: aarch64/vgic-v3 init sequence tests Eric Auger
2021-04-01  8:52   ` Eric Auger

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