Re: [PATCH 20/32] KVM: s390: pci: provide routines for enabling/disabling interpretation

Niklas Schnelle
2021-12-08T09:44:31Z

On Tue, 2021-12-07 at 15:57 -0500, Matthew Rosato wrote:
> These routines will be wired into the vfio_pci_zdev ioctl handlers to
> respond to requests to enable / disable a device for zPCI Load/Store
> interpretation.
>
> The first time such a request is received, enable the necessary facilities
> for the guest.
>
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
> arch/s390/include/asm/kvm_pci.h | 4 ++
> arch/s390/kvm/pci.c | 91 +++++++++++++++++++++++++++++++++
> arch/s390/pci/pci.c | 3 ++
> 3 files changed, 98 insertions(+)
>
> diff --git a/arch/s390/include/asm/kvm_pci.h b/arch/s390/include/asm/kvm_pci.h
> index 3e491a39704c..5d6283acb54c 100644
> --- a/arch/s390/include/asm/kvm_pci.h
>
---8<---
> return rc;
> + }
> +
> + /*
> + * Store information about the identity of the kvm guest allowed to
> + * access this device via interpretation to be used by host CLP
> + */
> + zdev->gd = gd;
> +
> + rc = zpci_enable_device(zdev);
> + if (rc)
> + goto err;
> +
> + /* Re-register the IOMMU that was already created */
> + rc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
> + (u64)zdev->dma_table);

The zdev->dma_table is a virtual address but we need an absolute
address in the MPCIFC so the above should use
virt_to_phys(zdev->dma_table) to be compatible with future V != R
kernel memory. As of now since virtual and absolute kernel addresses
are the same this is not a bug and we've had this (wrong) pattern in
the rest of the code but let's get it righht here from the start.

See also my commit "s390/pci: use physical addresses in DMA tables"
that is currently in the s390 feature branch.

> + if (rc)
> + goto err;
> +
> + return rc;
> +
> +err:
> + zdev->gd = 0;
> + return rc;
> +}
> +EXPORT_SYMBOL_GPL(kvm_s390_pci_interp_enable);
> +
> +int kvm_s390_pci_interp_disable(struct zpci_dev *zdev)
> +{
> + int rc;
> +
> + if (zdev->gd == 0)
> + return -EINVAL;
> +
> + /* Remove the host CLP guest designation */
> + zdev->gd = 0;
> +
> + if (zdev_enabled(zdev)) {
> + rc = zpci_disable_device(zdev);
> + if (rc)
> + return rc;
> + }
> +
> + rc = zpci_enable_device(zdev);
> + if (rc)
> + return rc;
> +
> + /* Re-register the IOMMU that was already created */
> + rc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
> + (u64)zdev->dma_table);

Same as above

> +
> + return rc;
> +}
> +EXPORT_SYMBOL_GPL(kvm_s390_pci_interp_disable);
> +
>
---8<---