On Sat, Mar 26, 2022 at 11:47:36PM +0000, Jag Raman wrote: > > > > On Mar 7, 2022, at 5:24 AM, Stefan Hajnoczi wrote: > > > > On Thu, Feb 17, 2022 at 02:49:02AM -0500, Jagannathan Raman wrote: > >> Forward remote device's interrupts to the guest > >> > >> Signed-off-by: Elena Ufimtseva > >> Signed-off-by: John G Johnson > >> Signed-off-by: Jagannathan Raman > >> --- > >> include/hw/pci/pci.h | 6 ++ > >> include/hw/remote/vfio-user-obj.h | 6 ++ > >> hw/pci/msi.c | 13 +++- > >> hw/pci/msix.c | 12 +++- > >> hw/remote/machine.c | 11 +-- > >> hw/remote/vfio-user-obj.c | 107 ++++++++++++++++++++++++++++++ > >> stubs/vfio-user-obj.c | 6 ++ > >> MAINTAINERS | 1 + > >> hw/remote/trace-events | 1 + > >> stubs/meson.build | 1 + > >> 10 files changed, 158 insertions(+), 6 deletions(-) > >> create mode 100644 include/hw/remote/vfio-user-obj.h > >> create mode 100644 stubs/vfio-user-obj.c > >> > >> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h > >> index c3f3c90473..d42d526a48 100644 > >> --- a/include/hw/pci/pci.h > >> +++ b/include/hw/pci/pci.h > >> @@ -129,6 +129,8 @@ typedef uint32_t PCIConfigReadFunc(PCIDevice *pci_dev, > >> typedef void PCIMapIORegionFunc(PCIDevice *pci_dev, int region_num, > >> pcibus_t addr, pcibus_t size, int type); > >> typedef void PCIUnregisterFunc(PCIDevice *pci_dev); > >> +typedef void PCIMSINotify(PCIDevice *pci_dev, unsigned vector); > >> +typedef void PCIMSIxNotify(PCIDevice *pci_dev, unsigned vector); > >> > >> typedef struct PCIIORegion { > >> pcibus_t addr; /* current PCI mapping address. -1 means not mapped */ > >> @@ -323,6 +325,10 @@ struct PCIDevice { > >> /* Space to store MSIX table & pending bit array */ > >> uint8_t *msix_table; > >> uint8_t *msix_pba; > >> + > >> + PCIMSINotify *msi_notify; > >> + PCIMSIxNotify *msix_notify; > >> + > >> /* MemoryRegion container for msix exclusive BAR setup */ > >> MemoryRegion msix_exclusive_bar; > >> /* Memory Regions for MSIX table and pending bit entries. */ > >> diff --git a/include/hw/remote/vfio-user-obj.h b/include/hw/remote/vfio-user-obj.h > >> new file mode 100644 > >> index 0000000000..87ab78b875 > >> --- /dev/null > >> +++ b/include/hw/remote/vfio-user-obj.h > >> @@ -0,0 +1,6 @@ > >> +#ifndef VFIO_USER_OBJ_H > >> +#define VFIO_USER_OBJ_H > >> + > >> +void vfu_object_set_bus_irq(PCIBus *pci_bus); > >> + > >> +#endif > >> diff --git a/hw/pci/msi.c b/hw/pci/msi.c > >> index 47d2b0f33c..93f5e400cc 100644 > >> --- a/hw/pci/msi.c > >> +++ b/hw/pci/msi.c > >> @@ -51,6 +51,8 @@ > >> */ > >> bool msi_nonbroken; > >> > >> +static void pci_msi_notify(PCIDevice *dev, unsigned int vector); > >> + > >> /* If we get rid of cap allocator, we won't need this. */ > >> static inline uint8_t msi_cap_sizeof(uint16_t flags) > >> { > >> @@ -225,6 +227,8 @@ int msi_init(struct PCIDevice *dev, uint8_t offset, > >> dev->msi_cap = config_offset; > >> dev->cap_present |= QEMU_PCI_CAP_MSI; > >> > >> + dev->msi_notify = pci_msi_notify; > > > > Are you sure it's correct to skip the msi_is_masked() logic? I think the > > callback function should only override the behavior of > > msi_send_message(), not the entire msi_notify() function. > > > > The same applies to MSI-X. > > Hi Stefan, > > We noticed that the client is handling the masking and unmasking of MSIx > interrupts. > > Concerning MSIx, vfio_msix_vector_use() handles unmasking and > vfio_msix_vector_release() handles masking operations. The server triggers > an MSIx interrupt by signaling the eventfd associated with the vector. If the vector > is unmasked, the interrupt bypasses the client/QEMU and takes this > path: “server -> KVM -> guest”. Whereas, if the vector is masked, it lands on the > client via: “server -> vfio_msi_interrupt()”. vfio_msi_interrupt() suppresses the > interrupt if the vector is masked. The use and release functions switch the server’s > eventfd between VFIOPCIDevice->VFIOMSIVector[i]->kvm_interrupt and > VFIOPCIDevice->VFIOMSIVector[i]->interrupt using the > VFIO_DEVICE_SET_IRQS message. > > Concerning MSI, the server should check if the vector is unmasked before > triggering. The server is not doing it presently, will update it. For some reason, > I had assumed that MSI handling is similar to MSIx in terms of masking - sorry > about that. The masking and unmasking information for MSI is in the config space > registers, so the server should have this information. > > You had previously suggested using callbacks for msi_get_message & > msi_send_message, considering the masking issue. Given MSIx masking > (including the MSIx table BAR) is handled at the client, the masking information > doesn’t reach the server - so msix_notify will never invoke the > msi_send_message callback - all the vectors remain masked at the server > end (msix_init() -> msix_mask_all()). I was expecting vfio-user devices to be involved in MSI-X masking so they can implement the Pending bit semantics described in the spec: If a masked vector has its Pending bit Set, and the associated underlying interrupt events are somehow satisfied (usually by software though the exact manner is Function-specific), the Function must Clear the Pending bit, to avoid sending a spurious interrupt message later when software unmasks the vector. Does QEMU VFIO support this? What happens when a hw/net/e1000e_core.c vfio-user device uses msix_clr_pending() and related APIs? Also, having the vfio-user daemon write to the eventfd while the vector is masked is a waste of CPU cycles. The PCIe spec describes using MSI-X masking for poll mode operation and going via eventfd is suboptimal: Software is permitted to mask one or more vectors indefinitely, and service their associated interrupt events strictly based on polling their Pending bits. A Function must Set and Clear its Pending bits as necessary to support this “pure polling” mode of operation. Maybe the answer is these issues don't matter in practice because MSI-X masking is not used much? Stefan