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RE: [RFC v6 09/24] vfio: Force nested if iommu requires it
From: |
Liu, Yi L |
Subject: |
RE: [RFC v6 09/24] vfio: Force nested if iommu requires it |
Date: |
Tue, 31 Mar 2020 08:34:21 +0000 |
> From: Auger Eric <address@hidden>
> Sent: Tuesday, March 31, 2020 4:05 PM
> To: Liu, Yi L <address@hidden>; address@hidden; qemu-
> Subject: Re: [RFC v6 09/24] vfio: Force nested if iommu requires it
>
> Yi,
>
> On 3/31/20 8:34 AM, Liu, Yi L wrote:
> > Hi Eric,
> >
> >> From: Eric Auger <address@hidden>
> >> Sent: Saturday, March 21, 2020 12:58 AM
> >> To: address@hidden; address@hidden; qemu-
> address@hidden;
> >> Subject: [RFC v6 09/24] vfio: Force nested if iommu requires it
> >>
> >> In case we detect the address space is translated by
> >> a virtual IOMMU which requires HW nested paging to
> >> integrate with VFIO, let's set up the container with
> >> the VFIO_TYPE1_NESTING_IOMMU iommu_type.
> >>
> >> Signed-off-by: Eric Auger <address@hidden>
> >>
> >> ---
> >>
> >> v4 -> v5:
> >> - fail immediatly if nested is wanted but not supported
> >>
> >> v2 -> v3:
> >> - add "nested only is selected if requested by @force_nested"
> >> comment in this patch
> >> ---
> >> hw/vfio/common.c | 36 ++++++++++++++++++++++++++++--------
> >> 1 file changed, 28 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> >> index 0b3593b3c0..ac417b5dbd 100644
> >> --- a/hw/vfio/common.c
> >> +++ b/hw/vfio/common.c
> >> @@ -1155,27 +1155,38 @@ static void
> vfio_put_address_space(VFIOAddressSpace
> >> *space)
> >> * vfio_get_iommu_type - selects the richest iommu_type (v2 first)
> >> */
> >> static int vfio_get_iommu_type(VFIOContainer *container,
> >> + bool want_nested,
> >> Error **errp)
> >> {
> >> - int iommu_types[] = { VFIO_TYPE1v2_IOMMU, VFIO_TYPE1_IOMMU,
> >> + int iommu_types[] = { VFIO_TYPE1_NESTING_IOMMU,
> >> + VFIO_TYPE1v2_IOMMU, VFIO_TYPE1_IOMMU,
> >> VFIO_SPAPR_TCE_v2_IOMMU, VFIO_SPAPR_TCE_IOMMU };
> >> - int i;
> >> + int i, ret = -EINVAL;
> >>
> >> for (i = 0; i < ARRAY_SIZE(iommu_types); i++) {
> >> if (ioctl(container->fd, VFIO_CHECK_EXTENSION, iommu_types[i])) {
> >> - return iommu_types[i];
> >> + if (iommu_types[i] == VFIO_TYPE1_NESTING_IOMMU &&
> >> !want_nested)
> {
> >> + continue;
> >> + }
> >> + ret = iommu_types[i];
> >> + break;
> >> }
> >> }
> >> - error_setg(errp, "No available IOMMU models");
> >> - return -EINVAL;
> >> + if (ret < 0) {
> >> + error_setg(errp, "No available IOMMU models");
> >> + } else if (want_nested && ret != VFIO_TYPE1_NESTING_IOMMU) {
> >> + error_setg(errp, "Nested mode requested but not supported");
> >> + ret = -EINVAL;
> >> + }
> >> + return ret;
> >> }
> >>
> >> static int vfio_init_container(VFIOContainer *container, int group_fd,
> >> - Error **errp)
> >> + bool want_nested, Error **errp)
> >> {
> >> int iommu_type, ret;
> >>
> >> - iommu_type = vfio_get_iommu_type(container, errp);
> >> + iommu_type = vfio_get_iommu_type(container, want_nested, errp);
> >> if (iommu_type < 0) {
> >> return iommu_type;
> >> }
> >> @@ -1211,6 +1222,14 @@ static int vfio_connect_container(VFIOGroup *group,
> >> AddressSpace *as,
> >> VFIOContainer *container;
> >> int ret, fd;
> >> VFIOAddressSpace *space;
> >> + IOMMUMemoryRegion *iommu_mr;
> >> + bool nested = false;
> >> +
> >> + if (as != &address_space_memory && memory_region_is_iommu(as->root))
> {
> >
> > I tried on my side. For virtual VT-d, it doesn't work as in intel_iommu,
> > we have a dynamic switch mechanism. Thus that, the
> > memory_region_is_iommu(as->root) won't return true as expected. I'm afraid
> > it doesn't work for virtual VT-d. So firstly, I'm wondering if
> > as != &address_space_memory is enough.
>
> (as != &address_space_memory) should be sufficient to tell that a vIOMMU
> is being used. But then, for example, you don't want to set nested
> paging for the virtio-iommu because virtio-iommu/VFIO uses notify-on-my
> (CM similar implementation). That's why I devised an attribute to
> retrieve the vIOMMU need for nested.
>
> Secondly, I'm considering if it is
> > good to let vfio_get_group() caller to provide a hint whether vIOMMU is
> > exposed. e.g. vfio_realize() in vfio/pci.c could figure out whether vIOMMU
> > is set easily. Thoughts?
> Sorry I don't get your point here. Why is it easier to figure out
> whether vIOMMU is set in vfio_realize()?
>
> pci_device_iommu_address_space(pdev) != &address_space_memory
> does determine whether a vIOMMU is in place, no?
>
No it's not just pci_device_iommu_address_space(pdev) != &address_space_memory,
I agree with your above comment, it's not enough to tell whether nesting is
needed or not. I'd like to add an API like pci_device_iommu_nesting_required(),
so that it can be determined. In the meanwhile, adding a query callback in
PCIIOMMUOps introduced in below pathc. Guess it works?
[v2,05/22] hw/pci: modify pci_setup_iommu() to set PCIIOMMUOps
https://patchwork.kernel.org/patch/11464577/
Regards,
Yi Liu
- [RFC v6 04/24] memory: Add IOMMU_ATTR_MSI_TRANSLATE IOMMU memory region attribute, (continued)
- [RFC v6 04/24] memory: Add IOMMU_ATTR_MSI_TRANSLATE IOMMU memory region attribute, Eric Auger, 2020/03/20
- [RFC v6 05/24] memory: Introduce IOMMU Memory Region inject_faults API, Eric Auger, 2020/03/20
- [RFC v6 06/24] memory: Add arch_id and leaf fields in IOTLBEntry, Eric Auger, 2020/03/20
- [RFC v6 07/24] iommu: Introduce generic header, Eric Auger, 2020/03/20
- [RFC v6 08/24] pci: introduce PCIPASIDOps to PCIDevice, Eric Auger, 2020/03/20
- [RFC v6 09/24] vfio: Force nested if iommu requires it, Eric Auger, 2020/03/20
- [RFC v6 10/24] vfio: Introduce hostwin_from_range helper, Eric Auger, 2020/03/20
- [RFC v6 11/24] vfio: Introduce helpers to DMA map/unmap a RAM section, Eric Auger, 2020/03/20
- [RFC v6 12/24] vfio: Set up nested stage mappings, Eric Auger, 2020/03/20
- [RFC v6 13/24] vfio: Pass stage 1 MSI bindings to the host, Eric Auger, 2020/03/20
- [RFC v6 14/24] vfio: Helper to get IRQ info including capabilities, Eric Auger, 2020/03/20
- [RFC v6 15/24] vfio/pci: Register handler for iommu fault, Eric Auger, 2020/03/20
- [RFC v6 17/24] vfio/pci: Implement the DMA fault handler, Eric Auger, 2020/03/20
- [RFC v6 16/24] vfio/pci: Set up the DMA FAULT region, Eric Auger, 2020/03/20
- [RFC v6 18/24] hw/arm/smmuv3: Advertise MSI_TRANSLATE attribute, Eric Auger, 2020/03/20
- [RFC v6 19/24] hw/arm/smmuv3: Store the PASID table GPA in the translation config, Eric Auger, 2020/03/20