Jean-Philippe Brucker
2023-Sep-06 13:20 UTC
[PATCH 2/2] iommu/virtio: Add ops->flush_iotlb_all and enable deferred flush
On Wed, Sep 06, 2023 at 09:55:49AM +0200, Niklas Schnelle wrote:> On Mon, 2023-09-04 at 17:33 +0100, Robin Murphy wrote: > > On 2023-09-04 16:34, Jean-Philippe Brucker wrote: > > > On Fri, Aug 25, 2023 at 05:21:26PM +0200, Niklas Schnelle wrote: > > > > Add ops->flush_iotlb_all operation to enable virtio-iommu for the > > > > dma-iommu deferred flush scheme. This results inn a significant increase > > > > > > in > > > > > > > in performance in exchange for a window in which devices can still > > > > access previously IOMMU mapped memory. To get back to the prior behavior > > > > iommu.strict=1 may be set on the kernel command line. > > > > > > Maybe add that it depends on CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT} as > > > well, because I've seen kernel configs that enable either. > > > > Indeed, I'd be inclined phrase it in terms of the driver now actually > > being able to honour lazy mode when requested (which happens to be the > > default on x86), rather than as if it might be some > > potentially-unexpected change in behaviour. > > > > Thanks, > > Robin. > > I kept running this series on a KVM guest on my private workstation > (QEMU v8.0.4) and while running iperf3 on a passed-through Intel 82599 > VF. I got a bunch of IOMMU events similar to the following as well as > card resets in the host. > > .. > [ 5959.338214] vfio-pci 0000:04:10.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0037 address=0x7b657064 flags=0x0000] > [ 5963.353429] ixgbe 0000:03:00.0 enp3s0: Detected Tx Unit Hang > Tx Queue <0> > TDH, TDT <93>, <9d> > next_to_use <9d> > next_to_clean <93> > tx_buffer_info[next_to_clean] > time_stamp <10019e800> > jiffies <10019ec80> > ... > > I retested on v6.5 vanilla (guest & host) and still get the above > errors so luckily for me it doesn't seem to be caused by the new code > but I can't reproduce it without virtio-iommu. Any idea what could > cause this?Adding Eric in case this looks familiar. I don't have hardware to test this but I guess QEMU system emulation may be able to reproduce the issue since it has an AMD IOMMU (unmaintained) and igb, I can give that a try. Thanks, Jean> > > > > > > Link: https://lore.kernel.org/lkml/20230802123612.GA6142 at myrica/ > > > > Signed-off-by: Niklas Schnelle <schnelle at linux.ibm.com> > > > > --- > > > > drivers/iommu/virtio-iommu.c | 12 ++++++++++++ > > > > 1 file changed, 12 insertions(+) > > > > > > > > diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c > > > > index fb73dec5b953..1b7526494490 100644 > > > > --- a/drivers/iommu/virtio-iommu.c > > > > +++ b/drivers/iommu/virtio-iommu.c > > > > @@ -924,6 +924,15 @@ static int viommu_iotlb_sync_map(struct iommu_domain *domain, > > > > return viommu_sync_req(vdomain->viommu); > > > > } > > > > > > > > +static void viommu_flush_iotlb_all(struct iommu_domain *domain) > > > > +{ > > > > + struct viommu_domain *vdomain = to_viommu_domain(domain); > > > > + > > > > + if (!vdomain->nr_endpoints) > > > > + return; > > > > > > As for patch 1, a NULL check in viommu_sync_req() would allow dropping > > > this one > > > > > > Thanks, > > > Jean > > Right, makes sense will move the check into viommu_sync_req() and add a > coment that it is there fore the cases where viommu_iotlb_sync() et al > get called before the IOMMU is set up. > > > > > > > > + viommu_sync_req(vdomain->viommu); > > > > +} > > > > + > > > > static void viommu_get_resv_regions(struct device *dev, struct list_head *head) > > > > { > > > > struct iommu_resv_region *entry, *new_entry, *msi = NULL; > > > > @@ -1049,6 +1058,8 @@ static bool viommu_capable(struct device *dev, enum iommu_cap cap) > > > > switch (cap) { > > > > case IOMMU_CAP_CACHE_COHERENCY: > > > > return true; > > > > + case IOMMU_CAP_DEFERRED_FLUSH: > > > > + return true; > > > > default: > > > > return false; > > > > } > > > > @@ -1069,6 +1080,7 @@ static struct iommu_ops viommu_ops = { > > > > .map_pages = viommu_map_pages, > > > > .unmap_pages = viommu_unmap_pages, > > > > .iova_to_phys = viommu_iova_to_phys, > > > > + .flush_iotlb_all = viommu_flush_iotlb_all, > > > > .iotlb_sync = viommu_iotlb_sync, > > > > .iotlb_sync_map = viommu_iotlb_sync_map, > > > > .free = viommu_domain_free, > > > > > > > > -- > > > > 2.39.2 > > > > >
Eric Auger
2023-Sep-07 14:21 UTC
[PATCH 2/2] iommu/virtio: Add ops->flush_iotlb_all and enable deferred flush
Hi, On 9/6/23 15:20, Jean-Philippe Brucker wrote:> On Wed, Sep 06, 2023 at 09:55:49AM +0200, Niklas Schnelle wrote: >> On Mon, 2023-09-04 at 17:33 +0100, Robin Murphy wrote: >>> On 2023-09-04 16:34, Jean-Philippe Brucker wrote: >>>> On Fri, Aug 25, 2023 at 05:21:26PM +0200, Niklas Schnelle wrote: >>>>> Add ops->flush_iotlb_all operation to enable virtio-iommu for the >>>>> dma-iommu deferred flush scheme. This results inn a significant increase >>>> in >>>> >>>>> in performance in exchange for a window in which devices can still >>>>> access previously IOMMU mapped memory. To get back to the prior behavior >>>>> iommu.strict=1 may be set on the kernel command line. >>>> Maybe add that it depends on CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT} as >>>> well, because I've seen kernel configs that enable either. >>> Indeed, I'd be inclined phrase it in terms of the driver now actually >>> being able to honour lazy mode when requested (which happens to be the >>> default on x86), rather than as if it might be some >>> potentially-unexpected change in behaviour. >>> >>> Thanks, >>> Robin. >> I kept running this series on a KVM guest on my private workstation >> (QEMU v8.0.4) and while running iperf3 on a passed-through Intel 82599 >> VF. I got a bunch of IOMMU events similar to the following as well as >> card resets in the host. >> >> .. >> [ 5959.338214] vfio-pci 0000:04:10.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0037 address=0x7b657064 flags=0x0000] >> [ 5963.353429] ixgbe 0000:03:00.0 enp3s0: Detected Tx Unit Hang >> Tx Queue <0> >> TDH, TDT <93>, <9d> >> next_to_use <9d> >> next_to_clean <93> >> tx_buffer_info[next_to_clean] >> time_stamp <10019e800> >> jiffies <10019ec80> >> ... >> >> I retested on v6.5 vanilla (guest & host) and still get the above >> errors so luckily for me it doesn't seem to be caused by the new code >> but I can't reproduce it without virtio-iommu. Any idea what could >> cause this? > Adding Eric in case this looks familiar.Unfortunately no idea of what could cause those page faults. On ther other hand I mostly test on ARM and INTEL. Thanks Eric> > I don't have hardware to test this but I guess QEMU system emulation may > be able to reproduce the issue since it has an AMD IOMMU (unmaintained) > and igb, I can give that a try. > > Thanks, > Jean > >>>>> Link: https://lore.kernel.org/lkml/20230802123612.GA6142 at myrica/ >>>>> Signed-off-by: Niklas Schnelle <schnelle at linux.ibm.com> >>>>> --- >>>>> drivers/iommu/virtio-iommu.c | 12 ++++++++++++ >>>>> 1 file changed, 12 insertions(+) >>>>> >>>>> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c >>>>> index fb73dec5b953..1b7526494490 100644 >>>>> --- a/drivers/iommu/virtio-iommu.c >>>>> +++ b/drivers/iommu/virtio-iommu.c >>>>> @@ -924,6 +924,15 @@ static int viommu_iotlb_sync_map(struct iommu_domain *domain, >>>>> return viommu_sync_req(vdomain->viommu); >>>>> } >>>>> >>>>> +static void viommu_flush_iotlb_all(struct iommu_domain *domain) >>>>> +{ >>>>> + struct viommu_domain *vdomain = to_viommu_domain(domain); >>>>> + >>>>> + if (!vdomain->nr_endpoints) >>>>> + return; >>>> As for patch 1, a NULL check in viommu_sync_req() would allow dropping >>>> this one >>>> >>>> Thanks, >>>> Jean >> Right, makes sense will move the check into viommu_sync_req() and add a >> coment that it is there fore the cases where viommu_iotlb_sync() et al >> get called before the IOMMU is set up. >> >>>>> + viommu_sync_req(vdomain->viommu); >>>>> +} >>>>> + >>>>> static void viommu_get_resv_regions(struct device *dev, struct list_head *head) >>>>> { >>>>> struct iommu_resv_region *entry, *new_entry, *msi = NULL; >>>>> @@ -1049,6 +1058,8 @@ static bool viommu_capable(struct device *dev, enum iommu_cap cap) >>>>> switch (cap) { >>>>> case IOMMU_CAP_CACHE_COHERENCY: >>>>> return true; >>>>> + case IOMMU_CAP_DEFERRED_FLUSH: >>>>> + return true; >>>>> default: >>>>> return false; >>>>> } >>>>> @@ -1069,6 +1080,7 @@ static struct iommu_ops viommu_ops = { >>>>> .map_pages = viommu_map_pages, >>>>> .unmap_pages = viommu_unmap_pages, >>>>> .iova_to_phys = viommu_iova_to_phys, >>>>> + .flush_iotlb_all = viommu_flush_iotlb_all, >>>>> .iotlb_sync = viommu_iotlb_sync, >>>>> .iotlb_sync_map = viommu_iotlb_sync_map, >>>>> .free = viommu_domain_free, >>>>> >>>>> -- >>>>> 2.39.2 >>>>>
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