Friendly ping to have your valuable inputs and comments. Thanks very much.
BRs, Jing > On 8/22/2023 3:29 PM, Jing Liu wrote: > Changes since RFC v1: > - RFC v1: https://www.mail-archive.com/qemu- > de...@nongnu.org/msg978637.html > - Revise the comments. (Alex) > - Report error of getting irq info and remove the trace of failure > case. (Alex, Cédric) > - Only store dynamic allocation flag as a bool type and test > accordingly. (Alex) > - Move dynamic allocation detection to vfio_msix_early_setup(). (Alex) > - Change the condition logic in vfio_msix_vector_do_use() that moving > the defer_kvm_irq_routing test out and create a common place to update > nr_vectors. (Alex) > - Consolidate the way of MSI-X enabling during device initialization and > interrupt restoring that uses fd = -1 trick. Create a function doing > that. (Alex) > > Before kernel v6.5, dynamic allocation of MSI-X interrupts was not supported. > Qemu therefore when allocating a new interrupt, should first release all > previously allocated interrupts (including disable of MSI-X) and re-allocate > all > interrupts that includes the new one. > > The kernel series [1] adds the support of dynamic MSI-X allocation to vfio-pci > and uses the existing flag VFIO_IRQ_INFO_NORESIZE to guide user space, that > when dynamic MSI-X is supported the flag is cleared. > > This series makes the behavior for VFIO PCI devices when dynamic MSI-X > allocation is supported. When guest unmasks an interrupt, Qemu can directly > allocate an interrupt on host for this and has nothing to do with the > previously > allocated ones. Therefore, host only allocates interrupts for those unmasked > (enabled) interrupts inside guest when dynamic MSI-X allocation is supported > by > device. > > When guests enable MSI-X with all of the vectors masked, Qemu need match the > state to enable MSI-X with no vector enabled. During migration restore, Qemu > also need enable MSI-X first in dynamic allocation mode, to avoid the guest > unused vectors being allocated on host. To consolidate them, we use vector 0 > with an invalid fd to get MSI-X enabled and create a common function for this. > This is cleaner than setting userspace triggering and immediately release. > > Any feedback is appreciated. > > Jing > > [1] https://lwn.net/Articles/931679/ > > Jing Liu (4): > vfio/pci: detect the support of dynamic MSI-X allocation > vfio/pci: enable vector on dynamic MSI-X allocation > vfio/pci: use an invalid fd to enable MSI-X > vfio/pci: enable MSI-X in interrupt restoring on dynamic allocation > > hw/vfio/pci.c | 126 +++++++++++++++++++++++++++++++++---------- > hw/vfio/pci.h | 1 + > hw/vfio/trace-events | 2 +- > 3 files changed, 101 insertions(+), 28 deletions(-) > > -- > 2.27.0
