Re: [Qemu-devel] [PATCH v2] ivshmem: add a new PIO BAR3(Doorbell) besides MMIO BAR0 to reduce notification time

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On Thu, Nov 17, 2011 at 10:50 PM,  <zanghongyong@xxxxxxxxxx> wrote:
> From: Hongyong Zang <zanghongyong@xxxxxxxxxx>
>
> This patch, adds a PIO BAR3 for guest notifying qemu. And we find the new notification way of PIO BAR3 reduces 30% time in comparison with the original MMIO BAR0 way.

Come to think of it, should we bump the PIO to BAR4 so that the shared
memory region could be made a 64-bit BAR and therefore take up BAR2
and BAR3?

>
> Signed-off-by: Hongyong Zang <zanghongyong@xxxxxxxxxx>
> ---
>  hw/ivshmem.c |   24 ++++++++++++++++++++++--
>  kvm-all.c    |   23 +++++++++++++++++++++++
>  kvm.h        |    1 +
>  3 files changed, 46 insertions(+), 2 deletions(-)
>
> diff --git a/hw/ivshmem.c b/hw/ivshmem.c
> index 242fbea..031cdd8 100644
> --- a/hw/ivshmem.c
> +++ b/hw/ivshmem.c
> @@ -29,6 +29,7 @@
>  #define IVSHMEM_MASTER  1
>
>  #define IVSHMEM_REG_BAR_SIZE 0x100
> +#define IVSHIO_REG_BAR_SIZE 0x10
>
>  //#define DEBUG_IVSHMEM
>  #ifdef DEBUG_IVSHMEM
> @@ -57,8 +58,10 @@ typedef struct IVShmemState {
>     CharDriverState **eventfd_chr;
>     CharDriverState *server_chr;
>     MemoryRegion ivshmem_mmio;
> +    MemoryRegion ivshmem_pio;
>
>     pcibus_t mmio_addr;
> +    pcibus_t pio_addr;
>     /* We might need to register the BAR before we actually have the memory.
>      * So prepare a container MemoryRegion for the BAR immediately and
>      * add a subregion when we have the memory.
> @@ -234,7 +237,7 @@ static uint64_t ivshmem_io_read(void *opaque, target_phys_addr_t addr,
>     return ret;
>  }
>
> -static const MemoryRegionOps ivshmem_mmio_ops = {
> +static const MemoryRegionOps ivshmem_io_ops = {
>     .read = ivshmem_io_read,
>     .write = ivshmem_io_write,
>     .endianness = DEVICE_NATIVE_ENDIAN,
> @@ -348,6 +351,8 @@ static void close_guest_eventfds(IVShmemState *s, int posn)
>     for (i = 0; i < guest_curr_max; i++) {
>         kvm_set_ioeventfd_mmio_long(s->peers[posn].eventfds[i],
>                     s->mmio_addr + DOORBELL, (posn << 16) | i, 0);
> +        kvm_set_ioeventfd_pio_long(s->peers[posn].eventfds[i],
> +                    s->pio_addr + DOORBELL, (posn << 16) | i, 0);
>         close(s->peers[posn].eventfds[i]);
>     }
>
> @@ -367,6 +372,12 @@ static void setup_ioeventfds(IVShmemState *s) {
>                                       true,
>                                       (i << 16) | j,
>                                       s->peers[i].eventfds[j]);
> +            memory_region_add_eventfd(&s->ivshmem_pio,
> +                                      DOORBELL,
> +                                      4,
> +                                      true,
> +                                      (i << 16) | j,
> +                                      s->peers[i].eventfds[j]);
>         }
>     }
>  }
> @@ -495,6 +506,10 @@ static void ivshmem_read(void *opaque, const uint8_t * buf, int flags)
>                         (incoming_posn << 16) | guest_max_eventfd, 1) < 0) {
>             fprintf(stderr, "ivshmem: ioeventfd not available\n");
>         }
> +        if (kvm_set_ioeventfd_pio_long(incoming_fd, s->pio_addr + DOORBELL,
> +                        (incoming_posn << 16) | guest_max_eventfd, 1) < 0) {
> +            fprintf(stderr, "ivshmem: ioeventfd not available\n");
> +        }
>     }
>
>     return;
> @@ -656,8 +671,10 @@ static int pci_ivshmem_init(PCIDevice *dev)
>
>     s->shm_fd = 0;
>
> -    memory_region_init_io(&s->ivshmem_mmio, &ivshmem_mmio_ops, s,
> +    memory_region_init_io(&s->ivshmem_mmio, &ivshmem_io_ops, s,
>                           "ivshmem-mmio", IVSHMEM_REG_BAR_SIZE);
> +    memory_region_init_io(&s->ivshmem_pio, &ivshmem_io_ops, s,
> +                          "ivshmem-pio", IVSHIO_REG_BAR_SIZE);
>
>     if (ivshmem_has_feature(s, IVSHMEM_IOEVENTFD)) {
>         setup_ioeventfds(s);
> @@ -666,6 +683,8 @@ static int pci_ivshmem_init(PCIDevice *dev)
>     /* region for registers*/
>     pci_register_bar(&s->dev, 0, PCI_BASE_ADDRESS_SPACE_MEMORY,
>                      &s->ivshmem_mmio);
> +    pci_register_bar(&s->dev, 3, PCI_BASE_ADDRESS_SPACE_IO,
> +                     &s->ivshmem_pio);
>
>     memory_region_init(&s->bar, "ivshmem-bar2-container", s->ivshmem_size);
>
> @@ -742,6 +761,7 @@ static int pci_ivshmem_uninit(PCIDevice *dev)
>     IVShmemState *s = DO_UPCAST(IVShmemState, dev, dev);
>
>     memory_region_destroy(&s->ivshmem_mmio);
> +    memory_region_destroy(&s->ivshmem_pio);
>     memory_region_del_subregion(&s->bar, &s->ivshmem);
>     memory_region_destroy(&s->ivshmem);
>     memory_region_destroy(&s->bar);
> diff --git a/kvm-all.c b/kvm-all.c
> index 5d500e1..737c2e2 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -1396,6 +1396,29 @@ int kvm_set_ioeventfd_mmio_long(int fd, uint32_t addr, uint32_t val, bool assign
>     return 0;
>  }
>
> +int kvm_set_ioeventfd_pio_long(int fd, uint32_t addr, uint32_t val, bool assign)
> +{
> +    struct kvm_ioeventfd kick = {
> +        .datamatch = val,
> +        .addr = addr,
> +        .len = 4,
> +        .flags = KVM_IOEVENTFD_FLAG_DATAMATCH | KVM_IOEVENTFD_FLAG_PIO,
> +        .fd = fd,
> +    };
> +    int r;
> +    if (!kvm_enabled()) {
> +        return -ENOSYS;
> +    }
> +    if (!assign) {
> +        kick.flags |= KVM_IOEVENTFD_FLAG_DEASSIGN;
> +    }
> +    r = kvm_vm_ioctl(kvm_state, KVM_IOEVENTFD, &kick);
> +    if (r < 0) {
> +        return r;
> +    }
> +    return 0;
> +}
> +
>  int kvm_set_ioeventfd_pio_word(int fd, uint16_t addr, uint16_t val, bool assign)
>  {
>     struct kvm_ioeventfd kick = {
> diff --git a/kvm.h b/kvm.h
> index b15e1dd..c2373c9 100644
> --- a/kvm.h
> +++ b/kvm.h
> @@ -198,6 +198,7 @@ int kvm_set_ioeventfd_mmio_long(int fd, uint32_t adr, uint32_t val, bool assign)
>
>  int kvm_set_irqfd(int gsi, int fd, bool assigned);
>
> +int kvm_set_ioeventfd_pio_long(int fd, uint32_t adr, uint32_t val, bool assign);
>  int kvm_set_ioeventfd_pio_word(int fd, uint16_t adr, uint16_t val, bool assign);
>
>  typedef struct KVMMsiMessage {
> --
> 1.7.1
>
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