2021-04-01 08:54:32

by Eric Auger

Subject: [PATCH v4 1/8] KVM: arm64: vgic-v3: Fix some error codes when setting RDIST base

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 <[email protected]>

---

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 */
+
+ if (!count)
+ return -EEXIST;
+
+ if (index != rdreg->index + 1)
return -EINVAL;
}

--
2.26.3

2021-04-01 10:55:43

by Marc Zyngier

Subject: Re: [PATCH v4 1/8] KVM: arm64: vgic-v3: Fix some error codes when setting RDIST base

Hi Eric,

On Thu, 01 Apr 2021 09:52:31 +0100,
Eric Auger <[email protected]> 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 <[email protected]>
>
> ---
>
> 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.

2021-04-01 18:33:56

by Eric Auger

Subject: Re: [PATCH v4 1/8] KVM: arm64: vgic-v3: Fix some error codes when setting RDIST base

Hi Marc,

On 4/1/21 12:52 PM, Marc Zyngier wrote:
> Hi Eric,
>
> On Thu, 01 Apr 2021 09:52:31 +0100,
> Eric Auger <[email protected]> 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 <[email protected]>
>>
>> ---
>>
>> 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:

Yes sometimes I can be "different" ;-)
>
> /* Don't mix single region and discrete redist regions */
> if (!count && rdreg->count)
> return -EINVAL;>
> Does it capture what you want to express?

yes it does!

Thanks

Eric
>
> Thanks,
>
> M.
>