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SubjectRe: [PATCH v5 2/2] s390: virtio: PV needs VIRTIO I/O device protection
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On 2020-07-09 11:55, Halil Pasic wrote:
> On Thu, 9 Jul 2020 10:57:33 +0200
> Cornelia Huck <cohuck@redhat.com> wrote:
>
>> On Thu, 9 Jul 2020 10:39:19 +0200
>> Pierre Morel <pmorel@linux.ibm.com> wrote:
>>
>>> If protected virtualization is active on s390, the virtio queues are
>>> not accessible to the host, unless VIRTIO_F_IOMMU_PLATFORM has been
>>> negotiated. Use the new arch_validate_virtio_features() interface to
>>> fail probe if that's not the case, preventing a host error on access
>>> attempt
>
> Punctuation at the end?
>
> Also 'that's not the case' refers to the negation
> 'VIRTIO_F_IOMMU_PLATFORM has been negotiated',
> arch_validate_virtio_features() is however part of
> virtio_finalize_features(), which is in turn part of the feature
> negotiation. But that is details. I'm fine with keeping the message as
> is.
>
>>>
>>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>>> ---
>>> arch/s390/mm/init.c | 27 +++++++++++++++++++++++++++
>>> 1 file changed, 27 insertions(+)
>>>
>>> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
>>> index 6dc7c3b60ef6..b8e6f90117da 100644
>>> --- a/arch/s390/mm/init.c
>>> +++ b/arch/s390/mm/init.c
>>> @@ -45,6 +45,7 @@
>>> #include <asm/kasan.h>
>>> #include <asm/dma-mapping.h>
>>> #include <asm/uv.h>
>>> +#include <linux/virtio_config.h>
>>>
>>> pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
>>>
>>> @@ -161,6 +162,32 @@ bool force_dma_unencrypted(struct device *dev)
>>> return is_prot_virt_guest();
>>> }
>>>
>>> +/*
>>> + * arch_validate_virtio_features
>>> + * @dev: the VIRTIO device being added
>>> + *
>>> + * Return an error if required features are missing on a guest running
>>> + * with protected virtualization.
>>> + */
>>> +int arch_validate_virtio_features(struct virtio_device *dev)
>>> +{
>>> + if (!is_prot_virt_guest())
>>> + return 0;
>>> +
>>> + if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
>>> + dev_warn(&dev->dev, "device must provide VIRTIO_F_VERSION_1\n");
>>
>> I'd probably use "legacy virtio not supported with protected
>> virtualization".
>>
>>> + return -ENODEV;
>>> + }
>>> +
>>> + if (!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
>>> + dev_warn(&dev->dev,
>>> + "device must provide VIRTIO_F_IOMMU_PLATFORM\n");
>>
>> "support for limited memory access required for protected
>> virtualization"
>>
>> ?
>>
>> Mentioning the feature flag is shorter in both cases, though.
>
> I liked the messages in v4. Why did we change those? Did somebody
> complain?
>
> I prefer the old ones, but it any case:
>
> Acked-by: Halil Pasic <pasic@linux.ibm.com>

Thanks,
Pierre


--
Pierre Morel
IBM Lab Boeblingen

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