On Thu, Dec 02, 2010 at 07:52:00PM +0800, Sheng Yang wrote: > On Thu, Dec 2, 2010 at 5:49 PM, Michael S. Tsirkin <m...@redhat.com> wrote: > > On Thu, Dec 02, 2010 at 09:13:28AM +0800, Yang, Sheng wrote: > >> On Wednesday 01 December 2010 22:03:58 Michael S. Tsirkin wrote: > >> > On Wed, Dec 01, 2010 at 04:41:38PM +0800, lidong chen wrote: > >> > > I used sr-iov, give each vm 2 vf. > >> > > after apply the patch, and i found performence is the same. > >> > > > >> > > the reason is in function msix_mmio_write, mostly addr is not in mmio > >> > > range. > >> > > > >> > > static int msix_mmio_write(struct kvm_io_device *this, gpa_t addr, int > >> > > len, > >> > > > >> > > const void *val) > >> > > > >> > > { > >> > > > >> > > struct kvm_assigned_dev_kernel *adev = > >> > > > >> > > container_of(this, struct kvm_assigned_dev_kernel, > >> > > > >> > > msix_mmio_dev); > >> > > > >> > > int idx, r = 0; > >> > > unsigned long new_val = *(unsigned long *)val; > >> > > > >> > > mutex_lock(&adev->kvm->lock); > >> > > if (!msix_mmio_in_range(adev, addr, len)) { > >> > > > >> > > // return here. > >> > > > >> > > r = -EOPNOTSUPP; > >> > > > >> > > goto out; > >> > > > >> > > } > >> > > > >> > > i printk the value: > >> > > addr start end len > >> > > F004C00C F0044000 F0044030 4 > >> > > > >> > > 00:06.0 Ethernet controller: Intel Corporation Unknown device 10ed (rev > >> > > 01) > >> > > > >> > > Subsystem: Intel Corporation Unknown device 000c > >> > > Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- > >> > > > >> > > Stepping- SERR- FastB2B- > >> > > > >> > > Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- > >> > > > >> > > <TAbort- <MAbort- >SERR- <PERR- > >> > > > >> > > Latency: 0 > >> > > Region 0: Memory at f0040000 (32-bit, non-prefetchable) [size=16K] > >> > > Region 3: Memory at f0044000 (32-bit, non-prefetchable) [size=16K] > >> > > Capabilities: [40] MSI-X: Enable+ Mask- TabSize=3 > >> > > > >> > > Vector table: BAR=3 offset=00000000 > >> > > PBA: BAR=3 offset=00002000 > >> > > > >> > > 00:07.0 Ethernet controller: Intel Corporation Unknown device 10ed (rev > >> > > 01) > >> > > > >> > > Subsystem: Intel Corporation Unknown device 000c > >> > > Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- > >> > > > >> > > Stepping- SERR- FastB2B- > >> > > > >> > > Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- > >> > > > >> > > <TAbort- <MAbort- >SERR- <PERR- > >> > > > >> > > Latency: 0 > >> > > Region 0: Memory at f0048000 (32-bit, non-prefetchable) [size=16K] > >> > > Region 3: Memory at f004c000 (32-bit, non-prefetchable) [size=16K] > >> > > Capabilities: [40] MSI-X: Enable+ Mask- TabSize=3 > >> > > > >> > > Vector table: BAR=3 offset=00000000 > >> > > PBA: BAR=3 offset=00002000 > >> > > > >> > > +static bool msix_mmio_in_range(struct kvm_assigned_dev_kernel *adev, > >> > > + gpa_t addr, int len) > >> > > +{ > >> > > + gpa_t start, end; > >> > > + > >> > > + BUG_ON(adev->msix_mmio_base == 0); > >> > > + start = adev->msix_mmio_base; > >> > > + end = adev->msix_mmio_base + PCI_MSIX_ENTRY_SIZE * > >> > > + adev->msix_max_entries_nr; > >> > > + if (addr >= start && addr + len <= end) > >> > > + return true; > >> > > + > >> > > + return false; > >> > > +} > >> > > >> > Hmm, this check looks wrong to me: there's no guarantee > >> > that guest uses the first N entries in the table. > >> > E.g. it could use a single entry, but only the last one. > >> > >> Please check the PCI spec. > > > > > > This is pretty explicit in the spec: the the last paragraph in the below: > > > > IMPLEMENTATION NOTE > > Handling MSI-X Vector Shortages > > > > Handling MSI-X Vector Shortages > > For the case where fewer vectors are allocated to a function than desired, > > You may not notice the premise here.
I noticed it. > Also check for "Table Size" would > help I think. It would help if msix_max_entries_nr was MSIX Table Size N (encoded in PCI config space as N - 1). Is this what it is? Maybe add this in some comment. > -- > regards, > Yang, Sheng > > software- > > controlled aliasing as enabled by MSI-X is one approach for handling the > > situation. For > > example, if a function supports five queues, each with an associated MSI-X > > table entry, but > > only three vectors are allocated, the function could be designed for > > software still to configure > > all five table entries, assigning one or more vectors to multiple table > > entries. Software could > > assign the three vectors {A,B,C} to the five entries as ABCCC, ABBCC, > > ABCBA, or other > > similar combinations. > > > > > > Alternatively, the function could be designed for software to configure it > > (using a device- > > specific mechanism) to use only three queues and three MSI-X table entries. > > Software could > > assign the three vectors {A,B,C} to the five entries as ABC--, A-B-C, > > A--CB, or other similar > > combinations. > > > > > > > >> -- > >> regards > >> Yang, Sheng > >> > >> > >> > > 2010/11/30 Yang, Sheng <sheng.y...@intel.com>: > >> > > > On Tuesday 30 November 2010 17:10:11 lidong chen wrote: > >> > > >> sr-iov also meet this problem, MSIX mask waste a lot of cpu > >> > > >> resource. > >> > > >> > >> > > >> I test kvm with sriov, which the vf driver could not disable msix. > >> > > >> so the host os waste a lot of cpu. cpu rate of host os is 90%. > >> > > >> > >> > > >> then I test xen with sriov, there ara also a lot of vm exits caused > >> > > >> by > >> > > >> MSIX mask. > >> > > >> but the cpu rate of xen and domain0 is less than kvm. cpu rate of > >> > > >> xen > >> > > >> and domain0 is 60%. > >> > > >> > >> > > >> without sr-iov, the cpu rate of xen and domain0 is higher than kvm. > >> > > >> > >> > > >> so i think the problem is kvm waste more cpu resource to deal with > >> > > >> MSIX mask. and we can see how xen deal with MSIX mask. > >> > > >> > >> > > >> if this problem sloved, maybe with MSIX enabled, the performace is > >> > > >> better. > >> > > > > >> > > > Please refer to my posted patches for this issue. > >> > > > > >> > > > http://www.spinics.net/lists/kvm/msg44992.html > >> > > > > >> > > > -- > >> > > > regards > >> > > > Yang, Sheng > >> > > > > >> > > >> 2010/11/23 Avi Kivity <a...@redhat.com>: > >> > > >> > On 11/23/2010 09:27 AM, lidong chen wrote: > >> > > >> >> can you tell me something about this problem. > >> > > >> >> thanks. > >> > > >> > > >> > > >> > Which problem? > >> > > >> > > >> > > >> > -- > >> > > >> > I have a truly marvellous patch that fixes the bug which this > >> > > >> > signature is too narrow to contain. > > -- > > To unsubscribe from this list: send the line "unsubscribe kvm" in > > the body of a message to majord...@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html