Re: [Qemu-devel] [PATCH v7 04/13] vfio: Add save and load functions for VFIO PCI devices

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Kirti Wankhede (kwankhede@nvidia.com) wrote:
> Sorry for delay to respond.
> 
> On 7/11/2019 5:37 PM, Dr. David Alan Gilbert wrote:
> > * Kirti Wankhede (kwankhede@nvidia.com) wrote:
> >> These functions save and restore PCI device specific data - config
> >> space of PCI device.
> >> Tested save and restore with MSI and MSIX type.
> >>
> >> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> >> Reviewed-by: Neo Jia <cjia@nvidia.com>
> >> ---
> >>  hw/vfio/pci.c                 | 114 ++++++++++++++++++++++++++++++++++++++++++
> >>  include/hw/vfio/vfio-common.h |   2 +
> >>  2 files changed, 116 insertions(+)
> >>
> >> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> >> index de0d286fc9dd..5fe4f8076cac 100644
> >> --- a/hw/vfio/pci.c
> >> +++ b/hw/vfio/pci.c
> >> @@ -2395,11 +2395,125 @@ static Object *vfio_pci_get_object(VFIODevice *vbasedev)
> >>      return OBJECT(vdev);
> >>  }
> >>  
> >> +static void vfio_pci_save_config(VFIODevice *vbasedev, QEMUFile *f)
> >> +{
> >> +    VFIOPCIDevice *vdev = container_of(vbasedev, VFIOPCIDevice, vbasedev);
> >> +    PCIDevice *pdev = &vdev->pdev;
> >> +    uint16_t pci_cmd;
> >> +    int i;
> >> +
> >> +    for (i = 0; i < PCI_ROM_SLOT; i++) {
> >> +        uint32_t bar;
> >> +
> >> +        bar = pci_default_read_config(pdev, PCI_BASE_ADDRESS_0 + i * 4, 4);
> >> +        qemu_put_be32(f, bar);
> >> +    }
> >> +
> >> +    qemu_put_be32(f, vdev->interrupt);
> >> +    if (vdev->interrupt == VFIO_INT_MSI) {
> >> +        uint32_t msi_flags, msi_addr_lo, msi_addr_hi = 0, msi_data;
> >> +        bool msi_64bit;
> >> +
> >> +        msi_flags = pci_default_read_config(pdev, pdev->msi_cap + PCI_MSI_FLAGS,
> >> +                                            2);
> >> +        msi_64bit = (msi_flags & PCI_MSI_FLAGS_64BIT);
> >> +
> >> +        msi_addr_lo = pci_default_read_config(pdev,
> >> +                                         pdev->msi_cap + PCI_MSI_ADDRESS_LO, 4);
> >> +        qemu_put_be32(f, msi_addr_lo);
> >> +
> >> +        if (msi_64bit) {
> >> +            msi_addr_hi = pci_default_read_config(pdev,
> >> +                                             pdev->msi_cap + PCI_MSI_ADDRESS_HI,
> >> +                                             4);
> >> +        }
> >> +        qemu_put_be32(f, msi_addr_hi);
> >> +
> >> +        msi_data = pci_default_read_config(pdev,
> >> +                pdev->msi_cap + (msi_64bit ? PCI_MSI_DATA_64 : PCI_MSI_DATA_32),
> >> +                2);
> >> +        qemu_put_be32(f, msi_data);
> >> +    } else if (vdev->interrupt == VFIO_INT_MSIX) {
> >> +        uint16_t offset;
> >> +
> >> +        /* save enable bit and maskall bit */
> >> +        offset = pci_default_read_config(pdev,
> >> +                                       pdev->msix_cap + PCI_MSIX_FLAGS + 1, 2);
> >> +        qemu_put_be16(f, offset);
> >> +        msix_save(pdev, f);
> >> +    }
> >> +    pci_cmd = pci_default_read_config(pdev, PCI_COMMAND, 2);
> >> +    qemu_put_be16(f, pci_cmd);
> >> +}
> >> +
> >> +static void vfio_pci_load_config(VFIODevice *vbasedev, QEMUFile *f)
> >> +{
> >> +    VFIOPCIDevice *vdev = container_of(vbasedev, VFIOPCIDevice, vbasedev);
> >> +    PCIDevice *pdev = &vdev->pdev;
> >> +    uint32_t interrupt_type;
> >> +    uint32_t msi_flags, msi_addr_lo, msi_addr_hi = 0, msi_data;
> >> +    uint16_t pci_cmd;
> >> +    bool msi_64bit;
> >> +    int i;
> >> +
> >> +    /* retore pci bar configuration */
> >> +    pci_cmd = pci_default_read_config(pdev, PCI_COMMAND, 2);
> >> +    vfio_pci_write_config(pdev, PCI_COMMAND,
> >> +                        pci_cmd & (!(PCI_COMMAND_IO | PCI_COMMAND_MEMORY)), 2);
> >> +    for (i = 0; i < PCI_ROM_SLOT; i++) {
> >> +        uint32_t bar = qemu_get_be32(f);
> >> +
> >> +        vfio_pci_write_config(pdev, PCI_BASE_ADDRESS_0 + i * 4, bar, 4);
> >> +    }
> > 
> > Is it possible to validate the bar's at all?  We just had a bug on a
> > virtual device where one version was asking for a larger bar than the
> > other; our validation caught this in some cases so we could tell that
> > the guest had a BAR that was aligned at the wrong alignment.
> > 
> 
> "Validate the bars" does that means validate size of bars?

I meant validate the address programmed into the BAR against the size,
assuming you know the size; e.g. if it's a 128MB BAR, then make sure the
address programmed in is 128MB aligned.

> >> +    vfio_pci_write_config(pdev, PCI_COMMAND,
> >> +                          pci_cmd | PCI_COMMAND_IO | PCI_COMMAND_MEMORY, 2);
> > 
> > Can you explain what this is for?  You write the command register at the
> > end of the function with the original value; there's no guarantee that
> > the device is using IO for example, so ORing it seems odd.
> > 
> 
> IO space and memory space accesses are disabled before writing BAR
> addresses, only those are enabled here.

But do you need to enable them here, or can it wait until the pci_cmd
write at the end of the function?

> > Also, are the other flags in COMMAND safe at this point - e.g. what
> > about interrupts and stuff?
> > 
> 
> COMMAND registers is saved from stop-and-copy phase, interrupt should be
> disabled, then restoring here when vCPU are not yet running.

Dave

> >> +    interrupt_type = qemu_get_be32(f);
> >> +
> >> +    if (interrupt_type == VFIO_INT_MSI) {
> >> +        /* restore msi configuration */
> >> +        msi_flags = pci_default_read_config(pdev,
> >> +                                            pdev->msi_cap + PCI_MSI_FLAGS, 2);
> >> +        msi_64bit = (msi_flags & PCI_MSI_FLAGS_64BIT);
> >> +
> >> +        vfio_pci_write_config(pdev, pdev->msi_cap + PCI_MSI_FLAGS,
> >> +                              msi_flags & (!PCI_MSI_FLAGS_ENABLE), 2);
> >> +
> >> +        msi_addr_lo = qemu_get_be32(f);
> >> +        vfio_pci_write_config(pdev, pdev->msi_cap + PCI_MSI_ADDRESS_LO,
> >> +                              msi_addr_lo, 4);
> >> +
> >> +        msi_addr_hi = qemu_get_be32(f);
> >> +        if (msi_64bit) {
> >> +            vfio_pci_write_config(pdev, pdev->msi_cap + PCI_MSI_ADDRESS_HI,
> >> +                                  msi_addr_hi, 4);
> >> +        }
> >> +        msi_data = qemu_get_be32(f);
> >> +        vfio_pci_write_config(pdev,
> >> +                pdev->msi_cap + (msi_64bit ? PCI_MSI_DATA_64 : PCI_MSI_DATA_32),
> >> +                msi_data, 2);
> >> +
> >> +        vfio_pci_write_config(pdev, pdev->msi_cap + PCI_MSI_FLAGS,
> >> +                              msi_flags | PCI_MSI_FLAGS_ENABLE, 2);
> >> +    } else if (interrupt_type == VFIO_INT_MSIX) {
> >> +        uint16_t offset = qemu_get_be16(f);
> >> +
> >> +        /* load enable bit and maskall bit */
> >> +        vfio_pci_write_config(pdev, pdev->msix_cap + PCI_MSIX_FLAGS + 1,
> >> +                              offset, 2);
> >> +        msix_load(pdev, f);
> >> +    }
> >> +    pci_cmd = qemu_get_be16(f);
> >> +    vfio_pci_write_config(pdev, PCI_COMMAND, pci_cmd, 2);
> >> +}
> >> +
> >>  static VFIODeviceOps vfio_pci_ops = {
> >>      .vfio_compute_needs_reset = vfio_pci_compute_needs_reset,
> >>      .vfio_hot_reset_multi = vfio_pci_hot_reset_multi,
> >>      .vfio_eoi = vfio_intx_eoi,
> >>      .vfio_get_object = vfio_pci_get_object,
> >> +    .vfio_save_config = vfio_pci_save_config,
> >> +    .vfio_load_config = vfio_pci_load_config,
> >>  };
> >>  
> >>  int vfio_populate_vga(VFIOPCIDevice *vdev, Error **errp)
> >> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> >> index 771b6d59a3db..ee72bd984a36 100644
> >> --- a/include/hw/vfio/vfio-common.h
> >> +++ b/include/hw/vfio/vfio-common.h
> >> @@ -120,6 +120,8 @@ struct VFIODeviceOps {
> >>      int (*vfio_hot_reset_multi)(VFIODevice *vdev);
> >>      void (*vfio_eoi)(VFIODevice *vdev);
> >>      Object *(*vfio_get_object)(VFIODevice *vdev);
> >> +    void (*vfio_save_config)(VFIODevice *vdev, QEMUFile *f);
> >> +    void (*vfio_load_config)(VFIODevice *vdev, QEMUFile *f);
> >>  };
> >>  
> >>  typedef struct VFIOGroup {
> >> -- 
> >> 2.7.0
> >>
> > --
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
> > 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK