Re: [Qemu-devel] [PATCH v2 2/2] spapr/irq: Only claim VALID interrupts at the KVM level

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Sep 11, 2019 at 03:39:37PM +0200, Cédric Le Goater wrote:
> A typical pseries VM with 16 vCPUs, one disk, one network adapater
> uses less than 100 interrupts but the whole IRQ number space of the
> QEMU machine is allocated at reset time and it is 8K wide. This is
> wasting a considerable amount of interrupt numbers in the global IRQ
> space which has 1M interrupts per socket on a POWER9.
> 
> To optimise the HW resources, only request at the KVM level interrupts
> which have been claimed by the guest. This will help to increase the
> maximum number of VMs per system and also help supporting nested guests
> using the XIVE interrupt mode.
> 
> Signed-off-by: Cédric Le Goater <clg@kaod.org>

Applied to ppc-for-4.2, thanks.

> ---
>  hw/intc/spapr_xive_kvm.c | 29 ++++++++++++++++++++++++++---
>  hw/intc/xics_kvm.c       |  8 ++++++++
>  2 files changed, 34 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
> index 17af4d19f54e..71b88d7797bc 100644
> --- a/hw/intc/spapr_xive_kvm.c
> +++ b/hw/intc/spapr_xive_kvm.c
> @@ -255,11 +255,16 @@ void kvmppc_xive_source_reset_one(XiveSource *xsrc, int srcno, Error **errp)
>  
>  static void kvmppc_xive_source_reset(XiveSource *xsrc, Error **errp)
>  {
> +    SpaprXive *xive = SPAPR_XIVE(xsrc->xive);
>      int i;
>  
>      for (i = 0; i < xsrc->nr_irqs; i++) {
>          Error *local_err = NULL;
>  
> +        if (!xive_eas_is_valid(&xive->eat[i])) {
> +            continue;
> +        }
> +
>          kvmppc_xive_source_reset_one(xsrc, i, &local_err);
>          if (local_err) {
>              error_propagate(errp, local_err);
> @@ -328,11 +333,18 @@ uint64_t kvmppc_xive_esb_rw(XiveSource *xsrc, int srcno, uint32_t offset,
>  
>  static void kvmppc_xive_source_get_state(XiveSource *xsrc)
>  {
> +    SpaprXive *xive = SPAPR_XIVE(xsrc->xive);
>      int i;
>  
>      for (i = 0; i < xsrc->nr_irqs; i++) {
> +        uint8_t pq;
> +
> +        if (!xive_eas_is_valid(&xive->eat[i])) {
> +            continue;
> +        }
> +
>          /* Perform a load without side effect to retrieve the PQ bits */
> -        uint8_t pq = xive_esb_read(xsrc, i, XIVE_ESB_GET);
> +        pq = xive_esb_read(xsrc, i, XIVE_ESB_GET);
>  
>          /* and save PQ locally */
>          xive_source_esb_set(xsrc, i, pq);
> @@ -521,9 +533,14 @@ static void kvmppc_xive_change_state_handler(void *opaque, int running,
>       */
>      if (running) {
>          for (i = 0; i < xsrc->nr_irqs; i++) {
> -            uint8_t pq = xive_source_esb_get(xsrc, i);
> +            uint8_t pq;
>              uint8_t old_pq;
>  
> +            if (!xive_eas_is_valid(&xive->eat[i])) {
> +                continue;
> +            }
> +
> +            pq = xive_source_esb_get(xsrc, i);
>              old_pq = xive_esb_read(xsrc, i, XIVE_ESB_SET_PQ_00 + (pq << 8));
>  
>              /*
> @@ -545,7 +562,13 @@ static void kvmppc_xive_change_state_handler(void *opaque, int running,
>       * migration is in progress.
>       */
>      for (i = 0; i < xsrc->nr_irqs; i++) {
> -        uint8_t pq = xive_esb_read(xsrc, i, XIVE_ESB_GET);
> +        uint8_t pq;
> +
> +        if (!xive_eas_is_valid(&xive->eat[i])) {
> +            continue;
> +        }
> +
> +        pq = xive_esb_read(xsrc, i, XIVE_ESB_GET);
>  
>          /*
>           * PQ is set to PENDING to possibly catch a triggered
> diff --git a/hw/intc/xics_kvm.c b/hw/intc/xics_kvm.c
> index a4d2e876cc5f..ba90d6dc966c 100644
> --- a/hw/intc/xics_kvm.c
> +++ b/hw/intc/xics_kvm.c
> @@ -190,6 +190,10 @@ void ics_get_kvm_state(ICSState *ics)
>      for (i = 0; i < ics->nr_irqs; i++) {
>          ICSIRQState *irq = &ics->irqs[i];
>  
> +        if (ics_irq_free(ics, i)) {
> +            continue;
> +        }
> +
>          kvm_device_access(kernel_xics_fd, KVM_DEV_XICS_GRP_SOURCES,
>                            i + ics->offset, &state, false, &error_fatal);
>  
> @@ -301,6 +305,10 @@ int ics_set_kvm_state(ICSState *ics, Error **errp)
>          Error *local_err = NULL;
>          int ret;
>  
> +        if (ics_irq_free(ics, i)) {
> +            continue;
> +        }
> +
>          ret = ics_set_kvm_state_one(ics, i, &local_err);
>          if (ret < 0) {
>              error_propagate(errp, local_err);

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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