Re: [Qemu-devel] [PATCH v3 03/19] xics: Disintricate allocation and type setting of interrupts

[Greg Kurz <groug@kaod.org>]

On Thu, 17 Jan 2019 18:14:46 +0100
Greg Kurz <groug@kaod.org> wrote:

> The current code assumes that an interrupt is allocated as soon as its
> type is set to MSI or LSI. PHB hotplug will require to be able to set
> the type of an interrupt before actually allocating it.
> 
> Disintricate type setting from allocation by using another flag bit for
> the latter. Introduce a new ics_claim_irq() function for allocation. The
> behavior of aborting if the same irq gets allocated twice is kept.
> 
> ics_set_irq_type() now only sets the type to MSI or LSI. It doesn't bring
> anything to abort if the type was already set before. Drop the assert
> and XICS_FLAGS_IRQ_MASK on the way.
> 

With some more testing (and thinking :) I now realize that the type of
the irq should survive PHB unplug, which is not the case with this patch.

This calls for a v4.

> Older QEMUs don't know about XICS_FLAGS_IRQ_CLAIMED. In order to safely
> handle incoming migration, we must fix the irq flags. This is done at
> post load thanks to a compat property. We don't need to do anything for
> backward migration since older machines only care for the irq type.
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
>  hw/core/machine.c     |    4 ++++
>  hw/intc/xics.c        |   28 +++++++++++++++++++++++++---
>  hw/ppc/pnv_psi.c      |    1 +
>  hw/ppc/spapr_irq.c    |    4 +---
>  include/hw/ppc/xics.h |    8 ++++++--
>  5 files changed, 37 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 1a0a9ab1117a..536a34092367 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -25,6 +25,10 @@
>  
>  GlobalProperty hw_compat_3_1[] = {
>      {
> +        .driver   = "ics-base",
> +        .property = "has-claimed-flag",
> +        .value    = "off",
> +    },{
>          .driver   = "pcie-root-port",
>          .property = "x-speed",
>          .value    = "2_5",
> diff --git a/hw/intc/xics.c b/hw/intc/xics.c
> index 16e8ffa2aaf7..82cf04548907 100644
> --- a/hw/intc/xics.c
> +++ b/hw/intc/xics.c
> @@ -75,7 +75,7 @@ void ics_pic_print_info(ICSState *ics, Monitor *mon)
>      for (i = 0; i < ics->nr_irqs; i++) {
>          ICSIRQState *irq = ics->irqs + i;
>  
> -        if (!(irq->flags & XICS_FLAGS_IRQ_MASK)) {
> +        if (!(irq->flags & XICS_FLAGS_IRQ_CLAIMED)) {
>              continue;
>          }
>          monitor_printf(mon, "  %4x %s %02x %02x\n",
> @@ -662,6 +662,22 @@ static int ics_base_dispatch_post_load(void *opaque, int version_id)
>      ICSState *ics = opaque;
>      ICSStateClass *info = ICS_BASE_GET_CLASS(ics);
>  
> +    if (!ics->has_claimed_flag) {
> +        int i;
> +
> +        for (i = 0; i < ics->nr_irqs; i++) {
> +            ICSIRQState *irq = ics->irqs + i;
> +
> +            /*
> +             * For older machines, allocating the irq and setting its type is
> +             * the same thing.
> +             */
> +            if (irq->flags & (XICS_FLAGS_IRQ_LSI| XICS_FLAGS_IRQ_MSI)) {
> +                irq->flags |= XICS_FLAGS_IRQ_CLAIMED;
> +            }
> +        }
> +    }
> +
>      if (info->post_load) {
>          return info->post_load(ics, version_id);
>      }
> @@ -702,6 +718,7 @@ static const VMStateDescription vmstate_ics_base = {
>  
>  static Property ics_base_properties[] = {
>      DEFINE_PROP_UINT32("nr-irqs", ICSState, nr_irqs, 0),
> +    DEFINE_PROP_BOOL("has-claimed-flag", ICSState, has_claimed_flag, true),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> @@ -741,10 +758,15 @@ ICPState *xics_icp_get(XICSFabric *xi, int server)
>      return xic->icp_get(xi, server);
>  }
>  
> -void ics_set_irq_type(ICSState *ics, int srcno, bool lsi)
> +void ics_claim_irq(ICSState *ics, int srcno)
>  {
> -    assert(!(ics->irqs[srcno].flags & XICS_FLAGS_IRQ_MASK));
> +    assert(ICS_IRQ_FREE(ics, srcno));
> +
> +    ics->irqs[srcno].flags |= XICS_FLAGS_IRQ_CLAIMED;
> +}
>  
> +void ics_set_irq_type(ICSState *ics, int srcno, bool lsi)
> +{
>      ics->irqs[srcno].flags |=
>          lsi ? XICS_FLAGS_IRQ_LSI : XICS_FLAGS_IRQ_MSI;
>  }
> diff --git a/hw/ppc/pnv_psi.c b/hw/ppc/pnv_psi.c
> index 8ced09506321..ced34e1119dc 100644
> --- a/hw/ppc/pnv_psi.c
> +++ b/hw/ppc/pnv_psi.c
> @@ -488,6 +488,7 @@ static void pnv_psi_realize(DeviceState *dev, Error **errp)
>  
>      for (i = 0; i < ics->nr_irqs; i++) {
>          ics_set_irq_type(ics, i, true);
> +        ics_claim_irq(ics, i);
>      }
>  
>      psi->qirqs = qemu_allocate_irqs(ics_simple_set_irq, ics, ics->nr_irqs);
> diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
> index 1da7a32348fc..86c712d15382 100644
> --- a/hw/ppc/spapr_irq.c
> +++ b/hw/ppc/spapr_irq.c
> @@ -125,9 +125,6 @@ error:
>      error_propagate(errp, local_err);
>  }
>  
> -#define ICS_IRQ_FREE(ics, srcno)   \
> -    (!((ics)->irqs[(srcno)].flags & (XICS_FLAGS_IRQ_MASK)))
> -
>  static int spapr_irq_claim_xics(sPAPRMachineState *spapr, int irq, bool lsi,
>                                  Error **errp)
>  {
> @@ -146,6 +143,7 @@ static int spapr_irq_claim_xics(sPAPRMachineState *spapr, int irq, bool lsi,
>      }
>  
>      ics_set_irq_type(ics, irq - ics->offset, lsi);
> +    ics_claim_irq(ics, irq - ics->offset);
>      return 0;
>  }
>  
> diff --git a/include/hw/ppc/xics.h b/include/hw/ppc/xics.h
> index fad786e8b22d..e3be5cc663c5 100644
> --- a/include/hw/ppc/xics.h
> +++ b/include/hw/ppc/xics.h
> @@ -131,6 +131,7 @@ struct ICSState {
>      /*< public >*/
>      uint32_t nr_irqs;
>      uint32_t offset;
> +    bool has_claimed_flag;
>      ICSIRQState *irqs;
>      XICSFabric *xics;
>  };
> @@ -153,13 +154,15 @@ struct ICSIRQState {
>  #define XICS_STATUS_PRESENTED          0x10
>  #define XICS_STATUS_QUEUED             0x20
>      uint8_t status;
> -/* (flags & XICS_FLAGS_IRQ_MASK) == 0 means the interrupt is not allocated */
>  #define XICS_FLAGS_IRQ_LSI             0x1
>  #define XICS_FLAGS_IRQ_MSI             0x2
> -#define XICS_FLAGS_IRQ_MASK            0x3
> +#define XICS_FLAGS_IRQ_CLAIMED         0x4
>      uint8_t flags;
>  };
>  
> +#define ICS_IRQ_FREE(ics, srcno)   \
> +    (!((ics)->irqs[(srcno)].flags & (XICS_FLAGS_IRQ_CLAIMED)))
> +
>  struct XICSFabric {
>      Object parent;
>  };
> @@ -193,6 +196,7 @@ void ics_simple_write_xive(ICSState *ics, int nr, int server,
>  void ics_simple_set_irq(void *opaque, int srcno, int val);
>  void ics_kvm_set_irq(void *opaque, int srcno, int val);
>  
> +void ics_claim_irq(ICSState *ics, int srcno);
>  void ics_set_irq_type(ICSState *ics, int srcno, bool lsi);
>  void icp_pic_print_info(ICPState *icp, Monitor *mon);
>  void ics_pic_print_info(ICSState *ics, Monitor *mon);
>