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Re: [PATCH v2 2/3] s390x/pci: Honor DMA limits set by vfio
From: |
Thomas Huth |
Subject: |
Re: [PATCH v2 2/3] s390x/pci: Honor DMA limits set by vfio |
Date: |
Tue, 15 Sep 2020 14:54:56 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 |
On 15/09/2020 00.29, Matthew Rosato wrote:
> When an s390 guest is using lazy unmapping, it can result in a very
> large number of oustanding DMA requests, far beyond the default
> limit configured for vfio. Let's track DMA usage similar to vfio
> in the host, and trigger the guest to flush their DMA mappings
> before vfio runs out.
>
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
> hw/s390x/s390-pci-bus.c | 99
> +++++++++++++++++++++++++++++++++++++++++++++---
> hw/s390x/s390-pci-bus.h | 9 +++++
> hw/s390x/s390-pci-inst.c | 29 +++++++++++---
> hw/s390x/s390-pci-inst.h | 3 ++
> 4 files changed, 129 insertions(+), 11 deletions(-)
>
> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
> index 92146a2..23474cd 100644
> --- a/hw/s390x/s390-pci-bus.c
> +++ b/hw/s390x/s390-pci-bus.c
> @@ -11,6 +11,8 @@
> * directory.
> */
>
> +#include <sys/ioctl.h>
> +
> #include "qemu/osdep.h"
> #include "qapi/error.h"
> #include "qapi/visitor.h"
> @@ -24,6 +26,9 @@
> #include "qemu/error-report.h"
> #include "qemu/module.h"
>
> +#include "hw/vfio/pci.h"
> +#include "hw/vfio/vfio-common.h"
> +
> #ifndef DEBUG_S390PCI_BUS
> #define DEBUG_S390PCI_BUS 0
> #endif
> @@ -737,6 +742,82 @@ static void s390_pci_iommu_free(S390pciState *s, PCIBus
> *bus, int32_t devfn)
> object_unref(OBJECT(iommu));
> }
>
> +static bool s390_sync_dma_avail(int fd, unsigned int *avail)
> +{
> + struct vfio_iommu_type1_info *info;
You could use g_autofree to get rid of the g_free() at the end.
> + uint32_t argsz;
> + bool rval = false;
> + int ret;
> +
> + if (avail == NULL) {
> + return false;
> + }
Since this is a "static" local function, and calling it with avail ==
NULL does not make too much sense, I think I'd rather turn this into an
assert() instead.
> + argsz = sizeof(struct vfio_iommu_type1_info);
> + info = g_malloc0(argsz);
> + info->argsz = argsz;
> + /*
> + * If the specified argsz is not large enough to contain all
> + * capabilities it will be updated upon return. In this case
> + * use the updated value to get the entire capability chain.
> + */
> + ret = ioctl(fd, VFIO_IOMMU_GET_INFO, info);
> + if (argsz != info->argsz) {
> + argsz = info->argsz;
> + info = g_realloc(info, argsz);
> + info->argsz = argsz;
> + ret = ioctl(fd, VFIO_IOMMU_GET_INFO, info);
> + }
> +
> + if (ret) {
> + goto out;
> + }
> +
> + /* If the capability exists, update with the current value */
> + rval = vfio_get_info_dma_avail(info, avail);
> +
> +out:
> + g_free(info);
> + return rval;
> +}
> +
> +static S390PCIDMACount *s390_start_dma_count(S390pciState *s, VFIODevice
> *vdev)
> +{
> + int id = vdev->group->container->fd;
> + S390PCIDMACount *cnt;
> + uint32_t avail;
> +
> + if (!s390_sync_dma_avail(id, &avail)) {
> + return NULL;
> + }
> +
> + QTAILQ_FOREACH(cnt, &s->zpci_dma_limit, link) {
> + if (cnt->id == id) {
> + cnt->users++;
> + return cnt;
> + }
> + }
> +
> + cnt = g_new0(S390PCIDMACount, 1);
> + cnt->id = id;
> + cnt->users = 1;
> + cnt->avail = avail;
> + QTAILQ_INSERT_TAIL(&s->zpci_dma_limit, cnt, link);
> + return cnt;
> +}
> +
> +static void s390_end_dma_count(S390pciState *s, S390PCIDMACount *cnt)
> +{
> + if (cnt == NULL) {
> + return;
> + }
Either use assert() or drop this completely (since you're checking it at
the caller site already).
> + cnt->users--;
> + if (cnt->users == 0) {
> + QTAILQ_REMOVE(&s->zpci_dma_limit, cnt, link);
> + }
> +}
> +
> static void s390_pcihost_realize(DeviceState *dev, Error **errp)
> {
> PCIBus *b;
> @@ -764,6 +845,7 @@ static void s390_pcihost_realize(DeviceState *dev, Error
> **errp)
> s->bus_no = 0;
> QTAILQ_INIT(&s->pending_sei);
> QTAILQ_INIT(&s->zpci_devs);
> + QTAILQ_INIT(&s->zpci_dma_limit);
>
> css_register_io_adapters(CSS_IO_ADAPTER_PCI, true, false,
> S390_ADAPTER_SUPPRESSIBLE, errp);
> @@ -902,6 +984,7 @@ static void s390_pcihost_plug(HotplugHandler
> *hotplug_dev, DeviceState *dev,
> {
> S390pciState *s = S390_PCI_HOST_BRIDGE(hotplug_dev);
> PCIDevice *pdev = NULL;
> + VFIOPCIDevice *vpdev = NULL;
> S390PCIBusDevice *pbdev = NULL;
>
> if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_BRIDGE)) {
> @@ -941,17 +1024,20 @@ static void s390_pcihost_plug(HotplugHandler
> *hotplug_dev, DeviceState *dev,
> }
> }
>
> + pbdev->pdev = pdev;
> + pbdev->iommu = s390_pci_get_iommu(s, pci_get_bus(pdev), pdev->devfn);
> + pbdev->iommu->pbdev = pbdev;
> + pbdev->state = ZPCI_FS_DISABLED;
> +
> if (object_dynamic_cast(OBJECT(dev), "vfio-pci")) {
> pbdev->fh |= FH_SHM_VFIO;
> + vpdev = container_of(pbdev->pdev, VFIOPCIDevice, pdev);
> + pbdev->iommu->dma_limit = s390_start_dma_count(s,
> + &vpdev->vbasedev);
> } else {
> pbdev->fh |= FH_SHM_EMUL;
> }
>
> - pbdev->pdev = pdev;
> - pbdev->iommu = s390_pci_get_iommu(s, pci_get_bus(pdev), pdev->devfn);
> - pbdev->iommu->pbdev = pbdev;
> - pbdev->state = ZPCI_FS_DISABLED;
> -
> if (s390_pci_msix_init(pbdev)) {
> error_setg(errp, "MSI-X support is mandatory "
> "in the S390 architecture");
> @@ -1004,6 +1090,9 @@ static void s390_pcihost_unplug(HotplugHandler
> *hotplug_dev, DeviceState *dev,
> pbdev->fid = 0;
> QTAILQ_REMOVE(&s->zpci_devs, pbdev, link);
> g_hash_table_remove(s->zpci_table, &pbdev->idx);
> + if (pbdev->iommu->dma_limit) {
> + s390_end_dma_count(s, pbdev->iommu->dma_limit);
> + }
> qdev_unrealize(dev);
> }
> }
Thomas
- Re: [PATCH v2 1/3] vfio: Find DMA available capability, (continued)
[PATCH v2 3/3] vfio: Create shared routine for scanning info capabilities, Matthew Rosato, 2020/09/14
[PATCH v2 2/3] s390x/pci: Honor DMA limits set by vfio, Matthew Rosato, 2020/09/14
Re: [PATCH v2 2/3] s390x/pci: Honor DMA limits set by vfio,
Thomas Huth <=