From 9a51c9ee6ca6610e4ab89945e6c75eda3a265ceb Mon Sep 17 00:00:00 2001 From: Halil Pasic Date: Thu, 24 May 2018 19:58:27 +0200 Subject: vfio-ccw: add force unlimited prefetch property There is at least one guest (OS) such that although it does not rely on the guarantees provided by ORB 1 word 9 bit (aka unlimited prefetch, aka P bit) not being set, it fails to tell this to the machine. Usually this ain't a big deal, as the original purpose of the P bit is to allow for performance optimizations. vfio-ccw however can not provide the guarantees required if the bit is not set. It is not possible to implement support for the P bit not set without transitioning to lower level protocols for vfio-ccw. So let's give the user the opportunity to force setting the P bit, if the user knows this is safe. For self modifying channel programs forcing the P bit is not safe. If the P bit is forced for a self modifying channel program things are expected to break in strange ways. Let's also avoid warning multiple about P bit not set in the ORB in case P bit is not told to be forced, and designate the affected vfio-ccw device. Signed-off-by: Halil Pasic Suggested-by: Dong Jia Shi Acked-by: Jason J. Herne Tested-by: Jason J. Herne Message-Id: <20180524175828.3143-2-pasic@linux.ibm.com> Signed-off-by: Cornelia Huck --- hw/s390x/css.c | 3 +-- hw/vfio/ccw.c | 35 +++++++++++++++++++++++++++++++++++ 2 files changed, 36 insertions(+), 2 deletions(-) (limited to 'hw') diff --git a/hw/s390x/css.c b/hw/s390x/css.c index 56c3fa8c89..39ae5bbf7e 100644 --- a/hw/s390x/css.c +++ b/hw/s390x/css.c @@ -1204,8 +1204,7 @@ static IOInstEnding sch_handle_start_func_passthrough(SubchDev *sch) * Only support prefetch enable mode. * Only support 64bit addressing idal. */ - if (!(orb->ctrl0 & ORB_CTRL0_MASK_PFCH) || - !(orb->ctrl0 & ORB_CTRL0_MASK_C64)) { + if (!(orb->ctrl0 & ORB_CTRL0_MASK_C64)) { warn_report("vfio-ccw requires PFCH and C64 flags set"); sch_gen_unit_exception(sch); css_inject_io_interrupt(sch); diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c index 76e4e8c652..351b305e1a 100644 --- a/hw/vfio/ccw.c +++ b/hw/vfio/ccw.c @@ -33,8 +33,30 @@ typedef struct VFIOCCWDevice { uint64_t io_region_offset; struct ccw_io_region *io_region; EventNotifier io_notifier; + bool force_orb_pfch; + bool warned_orb_pfch; } VFIOCCWDevice; +static inline void warn_once(bool *warned, const char *fmt, ...) +{ + va_list ap; + + if (!warned || *warned) { + return; + } + *warned = true; + va_start(ap, fmt); + warn_vreport(fmt, ap); + va_end(ap); +} + +static inline void warn_once_pfch(VFIOCCWDevice *vcdev, SubchDev *sch, + const char *msg) +{ + warn_once(&vcdev->warned_orb_pfch, "vfio-ccw (devno %x.%x.%04x): %s", + sch->cssid, sch->ssid, sch->devno, msg); +} + static void vfio_ccw_compute_needs_reset(VFIODevice *vdev) { vdev->needs_reset = false; @@ -55,6 +77,18 @@ static IOInstEnding vfio_ccw_handle_request(SubchDev *sch) struct ccw_io_region *region = vcdev->io_region; int ret; + if (!(sch->orb.ctrl0 & ORB_CTRL0_MASK_PFCH)) { + if (!(vcdev->force_orb_pfch)) { + warn_once_pfch(vcdev, sch, "requires PFCH flag set"); + sch_gen_unit_exception(sch); + css_inject_io_interrupt(sch); + return IOINST_CC_EXPECTED; + } else { + sch->orb.ctrl0 |= ORB_CTRL0_MASK_PFCH; + warn_once_pfch(vcdev, sch, "PFCH flag forced"); + } + } + QEMU_BUILD_BUG_ON(sizeof(region->orb_area) != sizeof(ORB)); QEMU_BUILD_BUG_ON(sizeof(region->scsw_area) != sizeof(SCSW)); QEMU_BUILD_BUG_ON(sizeof(region->irb_area) != sizeof(IRB)); @@ -430,6 +464,7 @@ static void vfio_ccw_unrealize(DeviceState *dev, Error **errp) static Property vfio_ccw_properties[] = { DEFINE_PROP_STRING("sysfsdev", VFIOCCWDevice, vdev.sysfsdev), + DEFINE_PROP_BOOL("force-orb-pfch", VFIOCCWDevice, force_orb_pfch, false), DEFINE_PROP_END_OF_LIST(), }; -- cgit v1.2.3