Re: [PATCH v11 2/2] virtio-pci: implement No_Soft_Reset bit

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jul 02, 2024 at 02:36:14AM +0000, Chen, Jiqian wrote:
> On 2024/6/21 17:20, Chen, Jiqian wrote:
> > Hi MST,
> > 
> > On 2024/6/6 18:22, Jiqian Chen wrote:
> >> In current code, when guest does S3, virtio-gpu are reset due to the
> >> bit No_Soft_Reset is not set. After resetting, the display resources
> >> of virtio-gpu are destroyed, then the display can't come back and only
> >> show blank after resuming.
> >>
> >> Implement No_Soft_Reset bit of PCI_PM_CTRL register, then guest can check
> >> this bit, if this bit is set, the devices resetting will not be done, and
> >> then the display can work after resuming.
> >>
> >> No_Soft_Reset bit is implemented for all virtio devices, and was tested
> >> only on virtio-gpu device. Set it false by default for safety.
> >>
> >> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
> >> ---
> >>  hw/core/machine.c              |  1 +
> >>  hw/virtio/virtio-pci.c         | 29 +++++++++++++++++++++++++++++
> >>  include/hw/virtio/virtio-pci.h |  5 +++++
> >>  3 files changed, 35 insertions(+)
> >>
> >> diff --git a/hw/core/machine.c b/hw/core/machine.c
> >> index 77a356f232f5..b6af94edcd0a 100644
> >> --- a/hw/core/machine.c
> >> +++ b/hw/core/machine.c
> >> @@ -36,6 +36,7 @@
> >>  GlobalProperty hw_compat_9_0[] = {
> >>      {"arm-cpu", "backcompat-cntfrq", "true" },
> >>      {"vfio-pci", "skip-vsc-check", "false" },
> >> +    { "virtio-pci", "x-pcie-pm-no-soft-reset", "off" },
> >>  };
> >>  const size_t hw_compat_9_0_len = G_N_ELEMENTS(hw_compat_9_0);
> >>  
> >> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> >> index 1b63bcb3f15c..c881f853253c 100644
> >> --- a/hw/virtio/virtio-pci.c
> >> +++ b/hw/virtio/virtio-pci.c
> >> @@ -2230,6 +2230,11 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp)
> >>              pcie_cap_lnkctl_init(pci_dev);
> >>          }
> >>  
> >> +        if (proxy->flags & VIRTIO_PCI_FLAG_PM_NO_SOFT_RESET) {
> >> +            pci_set_word(pci_dev->config + pos + PCI_PM_CTRL,
> >> +                         PCI_PM_CTRL_NO_SOFT_RESET);
> >> +        }
> >> +
> >>          if (proxy->flags & VIRTIO_PCI_FLAG_INIT_PM) {
> >>              /* Init Power Management Control Register */
> >>              pci_set_word(pci_dev->wmask + pos + PCI_PM_CTRL,
> >> @@ -2292,11 +2297,33 @@ static void virtio_pci_reset(DeviceState *qdev)
> >>      }
> >>  }
> >>  
> >> +static bool virtio_pci_no_soft_reset(PCIDevice *dev)
> >> +{
> >> +    uint16_t pmcsr;
> >> +
> >> +    if (!pci_is_express(dev) || !dev->exp.pm_cap) {
> >> +        return false;
> >> +    }
> >> +
> >> +    pmcsr = pci_get_word(dev->config + dev->exp.pm_cap + PCI_PM_CTRL);
> >> +
> >> +    /*
> >> +     * When No_Soft_Reset bit is set and the device
> >> +     * is in D3hot state, don't reset device
> >> +     */
> >> +    return (pmcsr & PCI_PM_CTRL_NO_SOFT_RESET) &&
> >> +           (pmcsr & PCI_PM_CTRL_STATE_MASK) == 3;
> >> +}
> >> +
> >>  static void virtio_pci_bus_reset_hold(Object *obj, ResetType type)
> >>  {
> >>      PCIDevice *dev = PCI_DEVICE(obj);
> >>      DeviceState *qdev = DEVICE(obj);
> >>  
> >> +    if (virtio_pci_no_soft_reset(dev)) {
> >> +        return;
> >> +    }
> >> +
> >>      virtio_pci_reset(qdev);
> >>  
> >>      if (pci_is_express(dev)) {
> >> @@ -2336,6 +2363,8 @@ static Property virtio_pci_properties[] = {
> >>                      VIRTIO_PCI_FLAG_INIT_LNKCTL_BIT, true),
> >>      DEFINE_PROP_BIT("x-pcie-pm-init", VirtIOPCIProxy, flags,
> >>                      VIRTIO_PCI_FLAG_INIT_PM_BIT, true),
> >> +    DEFINE_PROP_BIT("x-pcie-pm-no-soft-reset", VirtIOPCIProxy, flags,
> >> +                    VIRTIO_PCI_FLAG_PM_NO_SOFT_RESET_BIT, false),
> >>      DEFINE_PROP_BIT("x-pcie-flr-init", VirtIOPCIProxy, flags,
> >>                      VIRTIO_PCI_FLAG_INIT_FLR_BIT, true),
> >>      DEFINE_PROP_BIT("aer", VirtIOPCIProxy, flags,
> >> diff --git a/include/hw/virtio/virtio-pci.h b/include/hw/virtio/virtio-pci.h
> >> index 59d88018c16a..9e67ba38c748 100644
> >> --- a/include/hw/virtio/virtio-pci.h
> >> +++ b/include/hw/virtio/virtio-pci.h
> >> @@ -43,6 +43,7 @@ enum {
> >>      VIRTIO_PCI_FLAG_INIT_FLR_BIT,
> >>      VIRTIO_PCI_FLAG_AER_BIT,
> >>      VIRTIO_PCI_FLAG_ATS_PAGE_ALIGNED_BIT,
> >> +    VIRTIO_PCI_FLAG_PM_NO_SOFT_RESET_BIT,
> >>  };
> >>  
> >>  /* Need to activate work-arounds for buggy guests at vmstate load. */
> >> @@ -79,6 +80,10 @@ enum {
> >>  /* Init Power Management */
> >>  #define VIRTIO_PCI_FLAG_INIT_PM (1 << VIRTIO_PCI_FLAG_INIT_PM_BIT)
> >>  
> >> +/* Init The No_Soft_Reset bit of Power Management */
> >> +#define VIRTIO_PCI_FLAG_PM_NO_SOFT_RESET \
> >> +  (1 << VIRTIO_PCI_FLAG_PM_NO_SOFT_RESET_BIT)
> >> +
> >>  /* Init Function Level Reset capability */
> >>  #define VIRTIO_PCI_FLAG_INIT_FLR (1 << VIRTIO_PCI_FLAG_INIT_FLR_BIT)
> >>  
> > I have added compatibility for old machine.
> > Do you have any other concerns about this patch?
> > 
> If you don't have other concerns. May I get your Review-by?

I'm testing this, and if ok will include it in the pull request.

> -- 
> Best regards,
> Jiqian Chen.