On Fri, Aug 24, 2012 at 08:19:50AM +0200, Jan Kiszka wrote:
> From: Jan Kiszka <jan.kis...@siemens.com>
>
> This optimization was once used in qemu-kvm to keep KVM route usage low.
> But now we solved that problem via lazy updates. It also tried to handle
> the case of vectors shared between different sources of the same device.
> However, this never really worked and will have to be addressed
> differently anyway. So drop this obsolete interface.
>
> We still need interfaces to clear pending vectors though. Provide
> msix_clear_vector and msix_clear_all_vectors for this.
>
> This also unbreaks MSI-X after reset for ivshmem and megasas as device
> models can't easily mark their vectors used afterward (megasas didn't
> even try).
>
> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
> ---
>
> This patch has been posted some moons again, and we had a discussion
> about the impact on the existing users. At that time, MSI-X refactoring
> for KVM support was not yet merged. Now it is, and it should be better
> much clearer that vector usage tracking has no business with that
> feature.
>
> hw/ivshmem.c | 20 -------------------
> hw/megasas.c | 4 ---
> hw/msix.c | 57 ++++++++++++------------------------------------------
> hw/msix.h | 5 +--
> hw/pci.h | 2 -
> hw/virtio-pci.c | 20 +++++++-----------
> 6 files changed, 23 insertions(+), 85 deletions(-)
>
> diff --git a/hw/ivshmem.c b/hw/ivshmem.c
> index 47f2a16..5ffff48 100644
> --- a/hw/ivshmem.c
> +++ b/hw/ivshmem.c
> @@ -523,28 +523,11 @@ static void ivshmem_read(void *opaque, const uint8_t *
> buf, int flags)
> return;
> }
>
> -/* Select the MSI-X vectors used by device.
> - * ivshmem maps events to vectors statically, so
> - * we just enable all vectors on init and after reset. */
> -static void ivshmem_use_msix(IVShmemState * s)
> -{
> - int i;
> -
> - if (!msix_present(&s->dev)) {
> - return;
> - }
> -
> - for (i = 0; i < s->vectors; i++) {
> - msix_vector_use(&s->dev, i);
> - }
> -}
> -
> static void ivshmem_reset(DeviceState *d)
> {
> IVShmemState *s = DO_UPCAST(IVShmemState, dev.qdev, d);
>
> s->intrstatus = 0;
> - ivshmem_use_msix(s);
> return;
> }
>
> @@ -586,8 +569,6 @@ static void ivshmem_setup_msi(IVShmemState * s)
>
> /* allocate QEMU char devices for receiving interrupts */
> s->eventfd_table = g_malloc0(s->vectors * sizeof(EventfdEntry));
> -
> - ivshmem_use_msix(s);
> }
>
> static void ivshmem_save(QEMUFile* f, void *opaque)
> @@ -629,7 +610,6 @@ static int ivshmem_load(QEMUFile* f, void *opaque, int
> version_id)
>
> if (ivshmem_has_feature(proxy, IVSHMEM_MSI)) {
> msix_load(&proxy->dev, f);
> - ivshmem_use_msix(proxy);
> } else {
> proxy->intrstatus = qemu_get_be32(f);
> proxy->intrmask = qemu_get_be32(f);
> diff --git a/hw/megasas.c b/hw/megasas.c
> index c35a15d..4766117 100644
> --- a/hw/megasas.c
> +++ b/hw/megasas.c
> @@ -2121,10 +2121,6 @@ static int megasas_scsi_init(PCIDevice *dev)
> pci_register_bar(&s->dev, 2, PCI_BASE_ADDRESS_SPACE_IO, &s->port_io);
> pci_register_bar(&s->dev, 3, bar_type, &s->queue_io);
>
> - if (megasas_use_msix(s)) {
> - msix_vector_use(&s->dev, 0);
> - }
> -
> if (!s->sas_addr) {
> s->sas_addr = ((NAA_LOCALLY_ASSIGNED_ID << 24) |
> IEEE_COMPANY_LOCALLY_ASSIGNED) << 36;
> diff --git a/hw/msix.c b/hw/msix.c
> index aea340b..163ce4c 100644
> --- a/hw/msix.c
> +++ b/hw/msix.c
> @@ -273,7 +273,6 @@ int msix_init(struct PCIDevice *dev, unsigned short
> nentries,
>
> dev->msix_table = g_malloc0(table_size);
> dev->msix_pba = g_malloc0(pba_size);
> - dev->msix_entry_used = g_malloc0(nentries * sizeof
> *dev->msix_entry_used);
>
> msix_mask_all(dev, nentries);
>
> @@ -326,16 +325,6 @@ int msix_init_exclusive_bar(PCIDevice *dev, unsigned
> short nentries,
> return 0;
> }
>
> -static void msix_free_irq_entries(PCIDevice *dev)
> -{
> - int vector;
> -
> - for (vector = 0; vector < dev->msix_entries_nr; ++vector) {
> - dev->msix_entry_used[vector] = 0;
> - msix_clr_pending(dev, vector);
> - }
> -}
> -
> /* Clean up resources for the device. */
> void msix_uninit(PCIDevice *dev, MemoryRegion *table_bar, MemoryRegion
> *pba_bar)
> {
> @@ -344,7 +333,6 @@ void msix_uninit(PCIDevice *dev, MemoryRegion *table_bar,
> MemoryRegion *pba_bar)
> }
> pci_del_capability(dev, PCI_CAP_ID_MSIX, MSIX_CAP_LENGTH);
> dev->msix_cap = 0;
> - msix_free_irq_entries(dev);
> dev->msix_entries_nr = 0;
> memory_region_del_subregion(pba_bar, &dev->msix_pba_mmio);
> memory_region_destroy(&dev->msix_pba_mmio);
> @@ -354,8 +342,6 @@ void msix_uninit(PCIDevice *dev, MemoryRegion *table_bar,
> MemoryRegion *pba_bar)
> memory_region_destroy(&dev->msix_table_mmio);
> g_free(dev->msix_table);
> dev->msix_table = NULL;
> - g_free(dev->msix_entry_used);
> - dev->msix_entry_used = NULL;
> dev->cap_present &= ~QEMU_PCI_CAP_MSIX;
> return;
> }
> @@ -390,7 +376,6 @@ void msix_load(PCIDevice *dev, QEMUFile *f)
> return;
> }
>
> - msix_free_irq_entries(dev);
> qemu_get_buffer(f, dev->msix_table, n * PCI_MSIX_ENTRY_SIZE);
> qemu_get_buffer(f, dev->msix_pba, (n + 7) / 8);
> msix_update_function_masked(dev);
> @@ -419,8 +404,9 @@ void msix_notify(PCIDevice *dev, unsigned vector)
> {
> MSIMessage msg;
>
> - if (vector >= dev->msix_entries_nr || !dev->msix_entry_used[vector])
> + if (vector >= dev->msix_entries_nr) {
> return;
> + }
> if (msix_is_masked(dev, vector)) {
> msix_set_pending(dev, vector);
> return;
> @@ -436,7 +422,7 @@ void msix_reset(PCIDevice *dev)
> if (!msix_present(dev)) {
> return;
> }
> - msix_free_irq_entries(dev);
> + msix_clear_all_vectors(dev);
> dev->config[dev->msix_cap + MSIX_CONTROL_OFFSET] &=
> ~dev->wmask[dev->msix_cap + MSIX_CONTROL_OFFSET];
> memset(dev->msix_table, 0, dev->msix_entries_nr * PCI_MSIX_ENTRY_SIZE);
> @@ -444,41 +430,24 @@ void msix_reset(PCIDevice *dev)
> msix_mask_all(dev, dev->msix_entries_nr);
> }
>
> -/* PCI spec suggests that devices make it possible for software to configure
> - * less vectors than supported by the device, but does not specify a standard
> - * mechanism for devices to do so.
> - *
> - * We support this by asking devices to declare vectors software is going to
> - * actually use, and checking this on the notification path. Devices that
> - * don't want to follow the spec suggestion can declare all vectors as used.
> */
> -
> -/* Mark vector as used. */
> -int msix_vector_use(PCIDevice *dev, unsigned vector)
> +/* Clear pending vector. */
> +void msix_clear_vector(PCIDevice *dev, unsigned vector)
> {
> - if (vector >= dev->msix_entries_nr)
> - return -EINVAL;
> - dev->msix_entry_used[vector]++;
> - return 0;
> -}
> -
I keep thinking we should instead call vector notifier
here, so that virtio can detect and handle cases where
kvm_virtio_pci_vq_vector_use fails.
ATM it just asserts.
Maybe I am wrong.
Let's delay this decision until 1.3.
> -/* Mark vector as unused. */
> -void msix_vector_unuse(PCIDevice *dev, unsigned vector)
> -{
> - if (vector >= dev->msix_entries_nr || !dev->msix_entry_used[vector]) {
> - return;
> - }
> - if (--dev->msix_entry_used[vector]) {
> - return;
> + if (msix_present(dev) && vector < dev->msix_entries_nr) {
> + msix_clr_pending(dev, vector);
> }
> - msix_clr_pending(dev, vector);
> }
>
> -void msix_unuse_all_vectors(PCIDevice *dev)
> +void msix_clear_all_vectors(PCIDevice *dev)
> {
> + unsigned int vector;
> +
> if (!msix_present(dev)) {
> return;
> }
> - msix_free_irq_entries(dev);
> + for (vector = 0; vector < dev->msix_entries_nr; ++vector) {
> + msix_clr_pending(dev, vector);
> + }
> }
>
> unsigned int msix_nr_vectors_allocated(const PCIDevice *dev)
> diff --git a/hw/msix.h b/hw/msix.h
> index 15211cb..5c2512a 100644
> --- a/hw/msix.h
> +++ b/hw/msix.h
> @@ -26,9 +26,8 @@ void msix_load(PCIDevice *dev, QEMUFile *f);
> int msix_enabled(PCIDevice *dev);
> int msix_present(PCIDevice *dev);
>
> -int msix_vector_use(PCIDevice *dev, unsigned vector);
> -void msix_vector_unuse(PCIDevice *dev, unsigned vector);
> -void msix_unuse_all_vectors(PCIDevice *dev);
> +void msix_clear_vector(PCIDevice *dev, unsigned vector);
> +void msix_clear_all_vectors(PCIDevice *dev);
>
> void msix_notify(PCIDevice *dev, unsigned vector);
>
> diff --git a/hw/pci.h b/hw/pci.h
> index 4b6ab3d..1b07450 100644
> --- a/hw/pci.h
> +++ b/hw/pci.h
> @@ -240,8 +240,6 @@ struct PCIDevice {
> /* Memory Regions for MSIX table and pending bit entries. */
> MemoryRegion msix_table_mmio;
> MemoryRegion msix_pba_mmio;
> - /* Reference-count for entries actually in use by driver. */
> - unsigned *msix_entry_used;
> /* MSIX function mask set or MSIX disabled */
> bool msix_function_masked;
> /* Version id needed for VMState */
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index 2a3d86f..f8ce01d 100644
> --- a/hw/virtio-pci.c
> +++ b/hw/virtio-pci.c
> @@ -137,9 +137,6 @@ static int virtio_pci_load_config(void * opaque, QEMUFile
> *f)
> } else {
> proxy->vdev->config_vector = VIRTIO_NO_VECTOR;
> }
> - if (proxy->vdev->config_vector != VIRTIO_NO_VECTOR) {
> - return msix_vector_use(&proxy->pci_dev, proxy->vdev->config_vector);
> - }
> return 0;
> }
>
> @@ -153,9 +150,6 @@ static int virtio_pci_load_queue(void * opaque, int n,
> QEMUFile *f)
> vector = VIRTIO_NO_VECTOR;
> }
> virtio_queue_set_vector(proxy->vdev, n, vector);
> - if (vector != VIRTIO_NO_VECTOR) {
> - return msix_vector_use(&proxy->pci_dev, vector);
> - }
> return 0;
> }
>
> @@ -268,7 +262,7 @@ static void virtio_ioport_write(void *opaque, uint32_t
> addr, uint32_t val)
> if (pa == 0) {
> virtio_pci_stop_ioeventfd(proxy);
> virtio_reset(proxy->vdev);
> - msix_unuse_all_vectors(&proxy->pci_dev);
> + msix_clear_all_vectors(&proxy->pci_dev);
> }
> else
> virtio_queue_set_addr(vdev, vdev->queue_sel, pa);
> @@ -295,7 +289,7 @@ static void virtio_ioport_write(void *opaque, uint32_t
> addr, uint32_t val)
>
> if (vdev->status == 0) {
> virtio_reset(proxy->vdev);
> - msix_unuse_all_vectors(&proxy->pci_dev);
> + msix_clear_all_vectors(&proxy->pci_dev);
> }
>
> /* Linux before 2.6.34 sets the device as OK without enabling
> @@ -307,18 +301,20 @@ static void virtio_ioport_write(void *opaque, uint32_t
> addr, uint32_t val)
> }
> break;
> case VIRTIO_MSI_CONFIG_VECTOR:
> - msix_vector_unuse(&proxy->pci_dev, vdev->config_vector);
> + msix_clear_vector(&proxy->pci_dev, vdev->config_vector);
> /* Make it possible for guest to discover an error took place. */
> - if (msix_vector_use(&proxy->pci_dev, val) < 0)
> + if (val >= vdev->nvectors) {
> val = VIRTIO_NO_VECTOR;
> + }
> vdev->config_vector = val;
> break;
> case VIRTIO_MSI_QUEUE_VECTOR:
> - msix_vector_unuse(&proxy->pci_dev,
> + msix_clear_vector(&proxy->pci_dev,
> virtio_queue_vector(vdev, vdev->queue_sel));
> /* Make it possible for guest to discover an error took place. */
> - if (msix_vector_use(&proxy->pci_dev, val) < 0)
> + if (val >= vdev->nvectors) {
> val = VIRTIO_NO_VECTOR;
> + }
> virtio_queue_set_vector(vdev, vdev->queue_sel, val);
> break;
> default:
> --
> 1.7.3.4
