From fcad0d2121976df4b422b4007a5eb7fcaac01134 Mon Sep 17 00:00:00 2001 From: Alexey Kardashevskiy Date: Tue, 13 Mar 2018 11:17:31 -0600 Subject: [PATCH] ppc/spapr, vfio: Turn off MSIX emulation for VFIO devices This adds a possibility for the platform to tell VFIO not to emulate MSIX so MMIO memory regions do not get split into chunks in flatview and the entire page can be registered as a KVM memory slot and make direct MMIO access possible for the guest. This enables the entire MSIX BAR mapping to the guest for the pseries platform in order to achieve the maximum MMIO preformance for certain devices. Tested on: LSI Logic / Symbios Logic SAS3008 PCI-Express Fusion-MPT SAS-3 (rev 02) Signed-off-by: Alexey Kardashevskiy Reviewed-by: David Gibson Signed-off-by: Alex Williamson --- hw/ppc/spapr.c | 7 +++++++ hw/vfio/pci.c | 13 +++++++++++++ 2 files changed, 20 insertions(+) diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c index 7e1c858566..032d03423f 100644 --- a/hw/ppc/spapr.c +++ b/hw/ppc/spapr.c @@ -2855,6 +2855,11 @@ static void spapr_set_modern_hotplug_events(Object *obj, bool value, spapr->use_hotplug_event_source = value; } +static bool spapr_get_msix_emulation(Object *obj, Error **errp) +{ + return true; +} + static char *spapr_get_resize_hpt(Object *obj, Error **errp) { sPAPRMachineState *spapr = SPAPR_MACHINE(obj); @@ -2936,6 +2941,8 @@ static void spapr_instance_init(Object *obj) object_property_set_description(obj, "vsmt", "Virtual SMT: KVM behaves as if this were" " the host's SMT mode", &error_abort); + object_property_add_bool(obj, "vfio-no-msix-emulation", + spapr_get_msix_emulation, NULL, NULL); } static void spapr_machine_finalizefn(Object *obj) diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c index 02974f4eb9..b9bc6cd310 100644 --- a/hw/vfio/pci.c +++ b/hw/vfio/pci.c @@ -1581,6 +1581,19 @@ static int vfio_msix_setup(VFIOPCIDevice *vdev, int pos, Error **errp) */ memory_region_set_enabled(&vdev->pdev.msix_pba_mmio, false); + /* + * The emulated machine may provide a paravirt interface for MSIX setup + * so it is not strictly necessary to emulate MSIX here. This becomes + * helpful when frequently accessed MMIO registers are located in + * subpages adjacent to the MSIX table but the MSIX data containing page + * cannot be mapped because of a host page size bigger than the MSIX table + * alignment. + */ + if (object_property_get_bool(OBJECT(qdev_get_machine()), + "vfio-no-msix-emulation", NULL)) { + memory_region_set_enabled(&vdev->pdev.msix_table_mmio, false); + } + return 0; } -- 2.39.2