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From:   Reinette Chatre <reinette.chatre@intel.com>
To:     jgg@nvidia.com, yishaih@nvidia.com,
        shameerali.kolothum.thodi@huawei.com, kevin.tian@intel.com,
        alex.williamson@redhat.com
Cc:     tglx@linutronix.de, darwi@linutronix.de, kvm@vger.kernel.org,
        dave.jiang@intel.com, jing2.liu@intel.com, ashok.raj@intel.com,
        fenghua.yu@intel.com, tom.zanussi@linux.intel.com,
        reinette.chatre@intel.com, linux-kernel@vger.kernel.org
Subject: [PATCH V3 10/10] vfio/pci: Clear VFIO_IRQ_INFO_NORESIZE for MSI-X
Date:   Tue, 18 Apr 2023 10:29:21 -0700
Message-Id: <6c057618833a180da2147bffadb98e07cb73e045.1681837892.git.reinette.chatre@intel.com>
In-Reply-To: <cover.1681837892.git.reinette.chatre@intel.com>
References: <cover.1681837892.git.reinette.chatre@intel.com>
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Dynamic MSI-X is supported. Clear VFIO_IRQ_INFO_NORESIZE
to provide guidance to user space.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---
Changes since V2:
- Use new vdev->has_dyn_msix property instead of calling
  pci_msix_can_alloc_dyn() directly. (Alex)

Changes since RFC V1:
- Only advertise VFIO_IRQ_INFO_NORESIZE for MSI-X devices that
  can actually support dynamic allocation. (Alex)

 drivers/vfio/pci/vfio_pci_core.c | 4 +++-
 include/uapi/linux/vfio.h        | 3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index a3635a8e54c8..4050ad3388c2 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -1114,7 +1114,9 @@ static int vfio_pci_ioctl_get_irq_info(struct vfio_pci_core_device *vdev,
 	if (info.index == VFIO_PCI_INTX_IRQ_INDEX)
 		info.flags |=
 			(VFIO_IRQ_INFO_MASKABLE | VFIO_IRQ_INFO_AUTOMASKED);
-	else
+	else if ((info.index != VFIO_PCI_MSIX_IRQ_INDEX) ||
+		 (info.index == VFIO_PCI_MSIX_IRQ_INDEX &&
+		  !vdev->has_dyn_msix))
 		info.flags |= VFIO_IRQ_INFO_NORESIZE;
 
 	return copy_to_user(arg, &info, minsz) ? -EFAULT : 0;
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 0552e8dcf0cb..1a36134cae5c 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -511,6 +511,9 @@ struct vfio_region_info_cap_nvlink2_lnkspd {
  * then add and unmask vectors, it's up to userspace to make the decision
  * whether to allocate the maximum supported number of vectors or tear
  * down setup and incrementally increase the vectors as each is enabled.
+ * Absence of the NORESIZE flag indicates that vectors can be enabled
+ * and disabled dynamically without impacting other vectors within the
+ * index.
  */
 struct vfio_irq_info {
 	__u32	argsz;
-- 
2.34.1