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Re: [PATCH v3 3/3] vfio: Avoid disabling and enabling vectors repeatedly
From: |
Shenming Lu |
Subject: |
Re: [PATCH v3 3/3] vfio: Avoid disabling and enabling vectors repeatedly in VFIO migration |
Date: |
Tue, 9 Mar 2021 15:25:52 +0800 |
User-agent: |
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.2.2 |
On 2021/3/3 5:26, Alex Williamson wrote:
>
> MST/Marcel,
>
> Do you have an Ack or objection to exporting msix_masked() as below?
Or could we use msix_function_masked instead as below? :-)
if (!pdev->msix_function_masked) {
for (nr = 0; nr < msix_nr_vectors_allocated(pdev); nr++) {
if (!msix_is_masked(pdev, nr)) {
max_vec = nr;
}
}
}
Thanks,
Shenming
> Thanks,
>
> Alex
>
> On Tue, 23 Feb 2021 10:22:25 +0800
> Shenming Lu <lushenming@huawei.com> wrote:
>
>> In VFIO migration resume phase and some guest startups, there are
>> already unmasked vectors in the vector table when calling
>> vfio_msix_enable(). So in order to avoid inefficiently disabling
>> and enabling vectors repeatedly, let's allocate all needed vectors
>> first and then enable these unmasked vectors one by one without
>> disabling.
>>
>> Signed-off-by: Shenming Lu <lushenming@huawei.com>
>> ---
>> hw/pci/msix.c | 2 +-
>> hw/vfio/pci.c | 20 +++++++++++++++++---
>> include/hw/pci/msix.h | 1 +
>> 3 files changed, 19 insertions(+), 4 deletions(-)
>>
>> diff --git a/hw/pci/msix.c b/hw/pci/msix.c
>> index ae9331cd0b..e057958fcd 100644
>> --- a/hw/pci/msix.c
>> +++ b/hw/pci/msix.c
>> @@ -131,7 +131,7 @@ static void msix_handle_mask_update(PCIDevice *dev, int
>> vector, bool was_masked)
>> }
>> }
>>
>> -static bool msix_masked(PCIDevice *dev)
>> +bool msix_masked(PCIDevice *dev)
>> {
>> return dev->config[dev->msix_cap + MSIX_CONTROL_OFFSET] &
>> MSIX_MASKALL_MASK;
>> }
>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
>> index f74be78209..088fd41926 100644
>> --- a/hw/vfio/pci.c
>> +++ b/hw/vfio/pci.c
>> @@ -569,6 +569,9 @@ static void vfio_msix_vector_release(PCIDevice *pdev,
>> unsigned int nr)
>>
>> static void vfio_msix_enable(VFIOPCIDevice *vdev)
>> {
>> + PCIDevice *pdev = &vdev->pdev;
>> + unsigned int nr, max_vec = 0;
>> +
>> vfio_disable_interrupts(vdev);
>>
>> vdev->msi_vectors = g_new0(VFIOMSIVector, vdev->msix->entries);
>> @@ -587,11 +590,22 @@ static void vfio_msix_enable(VFIOPCIDevice *vdev)
>> * triggering to userspace, then immediately release the vector, leaving
>> * the physical device with no vectors enabled, but MSI-X enabled, just
>> * like the guest view.
>> + * If there are already unmasked vectors (in migration resume phase and
>> + * some guest startups) which will be enabled soon, we can allocate all
>> + * of them here to avoid inefficiently disabling and enabling vectors
>> + * repeatedly later.
>> */
>> - vfio_msix_vector_do_use(&vdev->pdev, 0, NULL, NULL);
>> - vfio_msix_vector_release(&vdev->pdev, 0);
>> + if (!msix_masked(pdev)) {
>> + for (nr = 0; nr < msix_nr_vectors_allocated(pdev); nr++) {
>> + if (!msix_is_masked(pdev, nr)) {
>> + max_vec = nr;
>> + }
>> + }
>> + }
>> + vfio_msix_vector_do_use(pdev, max_vec, NULL, NULL);
>> + vfio_msix_vector_release(pdev, max_vec);
>>
>> - if (msix_set_vector_notifiers(&vdev->pdev, vfio_msix_vector_use,
>> + if (msix_set_vector_notifiers(pdev, vfio_msix_vector_use,
>> vfio_msix_vector_release, NULL)) {
>> error_report("vfio: msix_set_vector_notifiers failed");
>> }
>> diff --git a/include/hw/pci/msix.h b/include/hw/pci/msix.h
>> index 4c4a60c739..b3cd88e262 100644
>> --- a/include/hw/pci/msix.h
>> +++ b/include/hw/pci/msix.h
>> @@ -28,6 +28,7 @@ void msix_load(PCIDevice *dev, QEMUFile *f);
>>
>> int msix_enabled(PCIDevice *dev);
>> int msix_present(PCIDevice *dev);
>> +bool msix_masked(PCIDevice *dev);
>>
>> bool msix_is_masked(PCIDevice *dev, unsigned vector);
>> void msix_set_pending(PCIDevice *dev, unsigned vector);
>
> .
>