Messages in this thread | | | Subject | Re: [PATCH v7 2/2] s390: virtio: PV needs VIRTIO I/O device protection | From | Pierre Morel <> | Date | Wed, 22 Jul 2020 13:48:24 +0200 |
| |
On 2020-07-15 13:51, Michael S. Tsirkin wrote: > On Wed, Jul 15, 2020 at 06:16:59PM +0800, Jason Wang wrote: >> >> On 2020/7/15 下午5:50, Michael S. Tsirkin wrote: >>> On Wed, Jul 15, 2020 at 10:31:09AM +0200, Pierre Morel 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. >>>> >>>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com> >>>> Reviewed-by: Cornelia Huck <cohuck@redhat.com> >>>> Acked-by: Halil Pasic <pasic@linux.ibm.com> >>>> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> >>>> --- >>>> arch/s390/mm/init.c | 28 ++++++++++++++++++++++++++++ >>>> 1 file changed, 28 insertions(+) >>>> >>>> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c >>>> index 6dc7c3b60ef6..d39af6554d4f 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 +162,33 @@ 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, >>>> + "legacy virtio not supported with protected virtualization\n"); >>>> + return -ENODEV; >>>> + } >>>> + >>>> + if (!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) { >>>> + dev_warn(&dev->dev, >>>> + "support for limited memory access required for protected virtualization\n"); >>>> + return -ENODEV; >>>> + } >>>> + >>>> + return 0; >>>> +} >>>> + >>>> /* protected virtualization */ >>>> static void pv_init(void) >>>> { >>> What bothers me here is that arch code depends on virtio now. >>> It works even with a modular virtio when functions are inline, >>> but it seems fragile: e.g. it breaks virtio as an out of tree module, >>> since layout of struct virtio_device can change. >> >> >> The code was only called from virtio.c so it should be fine. >> >> And my understanding is that we don't need to care about the kABI issue >> during upstream development? >> >> Thanks > > No, but so far it has been convenient at least for me, for development, > to just be able to unload all of virtio and load a different version. > > >> >>> >>> I'm not sure what to do with this yet, will try to think about it >>> over the weekend. Thanks! >>> >>> >>>> -- >>>> 2.25.1 >
Hi Michael,
I am not sure to understand the problem so I may propose a wrong solution but, let's try:
Would a callback registration instead of a weak function solve the problem? The registrating function in core could test a parameter to check if the callback is in sync with the VIRTIO core.
What do you think?
Regards, Pierre
-- Pierre Morel IBM Lab Boeblingen
| |