Auger Eric
2020-May-07 12:43 UTC
[EXT] Re: [PATCH v5] iommu/virtio: Use page size bitmap supported by endpoint
Hi Bharat, On 5/7/20 1:24 PM, Bharat Bhushan wrote:> > >> -----Original Message----- >> From: Michael S. Tsirkin <mst at redhat.com> >> Sent: Wednesday, May 6, 2020 5:53 AM >> To: Bharat Bhushan <bbhushan2 at marvell.com> >> Cc: jean-philippe at linaro.org; joro at 8bytes.org; jasowang at redhat.com; >> virtualization at lists.linux-foundation.org; iommu at lists.linux-foundation.org; >> linux-kernel at vger.kernel.org; eric.auger.pro at gmail.com; eric.auger at redhat.com >> Subject: [EXT] Re: [PATCH v5] iommu/virtio: Use page size bitmap supported by >> endpoint >> >> External Email >> >> ---------------------------------------------------------------------- >> On Tue, May 05, 2020 at 03:00:04PM +0530, Bharat Bhushan wrote: >>> Different endpoint can support different page size, probe endpoint if >>> it supports specific page size otherwise use global page sizes. >>> >>> Signed-off-by: Bharat Bhushan <bbhushan2 at marvell.com> >>> --- >>> v4->v5: >>> - Rebase to Linux v5.7-rc4 >>> >>> v3->v4: >>> - Fix whitespace error >>> >>> v2->v3: >>> - Fixed error return for incompatible endpoint >>> - __u64 changed to __le64 in header file >>> >>> drivers/iommu/virtio-iommu.c | 48 ++++++++++++++++++++++++++++--- >>> include/uapi/linux/virtio_iommu.h | 7 +++++ >>> 2 files changed, 51 insertions(+), 4 deletions(-) >>> >>> diff --git a/drivers/iommu/virtio-iommu.c >>> b/drivers/iommu/virtio-iommu.c index d5cac4f46ca5..9513d2ab819e 100644 >>> --- a/drivers/iommu/virtio-iommu.c >>> +++ b/drivers/iommu/virtio-iommu.c >>> @@ -78,6 +78,7 @@ struct viommu_endpoint { >>> struct viommu_dev *viommu; >>> struct viommu_domain *vdomain; >>> struct list_head resv_regions; >>> + u64 pgsize_bitmap; >>> }; >>> >>> struct viommu_request { >>> @@ -415,6 +416,19 @@ static int viommu_replay_mappings(struct >> viommu_domain *vdomain) >>> return ret; >>> } >>> >>> +static int viommu_set_pgsize_bitmap(struct viommu_endpoint *vdev, >>> + struct virtio_iommu_probe_pgsize_mask *mask, >>> + size_t len) >>> +{ >>> + u64 pgsize_bitmap = le64_to_cpu(mask->pgsize_bitmap); >>> + >>> + if (len < sizeof(*mask)) >> >> This is too late to validate length, you have dereferenced it already. >> do it before the read pls. > > Yes, Will change here and other places as well > >> >>> + return -EINVAL; >> >> OK but note that guest will then just proceed to ignore the property. Is that really >> OK? Wouldn't host want to know? > > > Guest need to be in sync with device, so yes seems like guest need to tell device which page-size-mask it is using. > > Corresponding spec change patch (https://www.mail-archive.com/virtio-dev at lists.oasis-open.org/msg06214.html) > > Would like Jean/Eric to comment here as well.why can't we fail the probe request in that case? This is a misbehaving device that reports malformed property, right? Thanks Eric> >> >> >>> + >>> + vdev->pgsize_bitmap = pgsize_bitmap; >> >> what if bitmap is 0? Is that a valid size? I see a bunch of BUG_ON with that value ... > > As per spec proposed device is supposed to set at-least one bit. > Will add a bug_on her. > Should we add bug_on or switch to global config page-size mask if this is zero (notify device which page-size-mask it is using). > >> >> I also see a bunch of code like e.g. this: >> >> pg_size = 1UL << __ffs(pgsize_bitmap); >> >> which probably won't DTRT on a 32 bit guest if the bitmap has bits set in the high >> word. >> > > My thought is that in that case viommu_domain_finalise() will fail, do not proceed. > >> >> >>> + return 0; >>> +} >>> + >>> static int viommu_add_resv_mem(struct viommu_endpoint *vdev, >>> struct virtio_iommu_probe_resv_mem *mem, >>> size_t len) >>> @@ -499,6 +513,9 @@ static int viommu_probe_endpoint(struct viommu_dev >> *viommu, struct device *dev) >>> case VIRTIO_IOMMU_PROBE_T_RESV_MEM: >>> ret = viommu_add_resv_mem(vdev, (void *)prop, len); >>> break; >>> + case VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK: >>> + ret = viommu_set_pgsize_bitmap(vdev, (void *)prop, len); >>> + break; >>> default: >>> dev_err(dev, "unknown viommu prop 0x%x\n", type); >>> } >>> @@ -630,7 +647,7 @@ static int viommu_domain_finalise(struct >>> viommu_endpoint *vdev, >>> >>> vdomain->id = (unsigned int)ret; >>> >>> - domain->pgsize_bitmap = viommu->pgsize_bitmap; >>> + domain->pgsize_bitmap = vdev->pgsize_bitmap; >>> domain->geometry = viommu->geometry; >>> >>> vdomain->map_flags = viommu->map_flags; >>> @@ -654,6 +671,29 @@ static void viommu_domain_free(struct iommu_domain >> *domain) >>> kfree(vdomain); >>> } >>> >>> +/* >>> + * Check whether the endpoint's capabilities are compatible with >>> +other >>> + * endpoints in the domain. Report any inconsistency. >>> + */ >>> +static bool viommu_endpoint_is_compatible(struct viommu_endpoint *vdev, >>> + struct viommu_domain *vdomain) { >>> + struct device *dev = vdev->dev; >>> + >>> + if (vdomain->viommu != vdev->viommu) { >>> + dev_err(dev, "cannot attach to foreign vIOMMU\n"); >>> + return false; >>> + } >>> + >>> + if (vdomain->domain.pgsize_bitmap != vdev->pgsize_bitmap) { >>> + dev_err(dev, "incompatible domain bitmap 0x%lx != 0x%llx\n", >>> + vdomain->domain.pgsize_bitmap, vdev->pgsize_bitmap); >>> + return false; >>> + } >> >> I'm confused by this. So let's assume host supports pages sizes of 4k, 2M, 1G. It >> signals this in the properties. Nice. >> Now domain supports 4k, 2M and that's all. Why is that a problem? >> Just don't use 1G ... > > Is not it too to change the existing domain properties, for devices already attached to domain? New devices must match to domain page-size. > >> >> >>> + >>> + return true; >>> +} >>> + >>> static int viommu_attach_dev(struct iommu_domain *domain, struct >>> device *dev) { >>> int i; >>> @@ -670,9 +710,8 @@ static int viommu_attach_dev(struct iommu_domain >> *domain, struct device *dev) >>> * owns it. >>> */ >>> ret = viommu_domain_finalise(vdev, domain); >>> - } else if (vdomain->viommu != vdev->viommu) { >>> - dev_err(dev, "cannot attach to foreign vIOMMU\n"); >>> - ret = -EXDEV; >>> + } else if (!viommu_endpoint_is_compatible(vdev, vdomain)) { >>> + ret = -EINVAL; >>> } >>> mutex_unlock(&vdomain->mutex); >>> >>> @@ -886,6 +925,7 @@ static int viommu_add_device(struct device *dev) >>> >>> vdev->dev = dev; >>> vdev->viommu = viommu; >>> + vdev->pgsize_bitmap = viommu->pgsize_bitmap; >>> INIT_LIST_HEAD(&vdev->resv_regions); >>> dev_iommu_priv_set(dev, vdev); >>> >>> diff --git a/include/uapi/linux/virtio_iommu.h >>> b/include/uapi/linux/virtio_iommu.h >>> index 48e3c29223b5..2cced7accc99 100644 >>> --- a/include/uapi/linux/virtio_iommu.h >>> +++ b/include/uapi/linux/virtio_iommu.h >> >> As any virtio UAPI change, you need to copy virtio TC at some point before this is >> merged ... > > Jean already send patch for same > https://www.mail-archive.com/virtio-dev at lists.oasis-open.org/msg06214.html > > Do we need to do anything additional? > >> >>> @@ -111,6 +111,7 @@ struct virtio_iommu_req_unmap { >>> >>> #define VIRTIO_IOMMU_PROBE_T_NONE 0 >>> #define VIRTIO_IOMMU_PROBE_T_RESV_MEM 1 >>> +#define VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK 2 >>> >>> #define VIRTIO_IOMMU_PROBE_T_MASK 0xfff >>> >> >> Does host need to know that guest will ignore the page size mask? >> Maybe we need a feature bit. >> >>> @@ -119,6 +120,12 @@ struct virtio_iommu_probe_property { >>> __le16 length; >>> }; >>> >>> +struct virtio_iommu_probe_pgsize_mask { >>> + struct virtio_iommu_probe_property head; >>> + __u8 reserved[4]; >>> + __le64 pgsize_bitmap; >>> +}; >>> + >> >> This is UAPI. Document the format of pgsize_bitmap please. > > Ok, > > Thanks > -Bharat > >> >> >>> #define VIRTIO_IOMMU_RESV_MEM_T_RESERVED 0 >>> #define VIRTIO_IOMMU_RESV_MEM_T_MSI 1 >>> >>> -- >>> 2.17.1 >