From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37117) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dmbqo-0004kL-Mt for qemu-devel@nongnu.org; Tue, 29 Aug 2017 04:26:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dmbqk-0005su-Mo for qemu-devel@nongnu.org; Tue, 29 Aug 2017 04:26:22 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:57409 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dmbqk-0005sf-Gf for qemu-devel@nongnu.org; Tue, 29 Aug 2017 04:26:18 -0400 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v7T8OLES037234 for ; Tue, 29 Aug 2017 04:26:17 -0400 Received: from e37.co.us.ibm.com (e37.co.us.ibm.com [32.97.110.158]) by mx0b-001b2d01.pphosted.com with ESMTP id 2cn1hym7c6-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 29 Aug 2017 04:26:17 -0400 Received: from localhost by e37.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 29 Aug 2017 02:26:16 -0600 References: <1503907487-2764-1-git-send-email-zyimin@linux.vnet.ibm.com> <1503907487-2764-5-git-send-email-zyimin@linux.vnet.ibm.com> <20170828175722.0b54b59a.cohuck@redhat.com> <498a00ca-ea1a-ae09-0772-4a25c729841e@linux.vnet.ibm.com> <20170829100746.66c47fd8.cohuck@redhat.com> From: Yi Min Zhao Date: Tue, 29 Aug 2017 16:26:10 +0800 MIME-Version: 1.0 In-Reply-To: <20170829100746.66c47fd8.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Message-Id: <0d7cc071-cebe-82d5-90da-9737a5f0733e@linux.vnet.ibm.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH 4/4] s390x/pci: add iommu replay callback List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cornelia Huck Cc: qemu-devel@nongnu.org, borntraeger@de.ibm.com, pasic@linux.vnet.ibm.com, pmorel@linux.vnet.ibm.com, agraf@suse.de, richard.henderson@linaro.org =E5=9C=A8 2017/8/29 =E4=B8=8B=E5=8D=884:07, Cornelia Huck =E5=86=99=E9=81= =93: > [Restored cc:s. Please remember to do reply-all.] > > On Tue, 29 Aug 2017 12:46:51 +0800 > Yi Min Zhao wrote: > >> =E5=9C=A8 2017/8/28 =E4=B8=8B=E5=8D=8811:57, Cornelia Huck =E5=86=99=E9= =81=93: >>> On Mon, 28 Aug 2017 10:04:47 +0200 >>> Yi Min Zhao wrote: >>> >>>> Let's introduce iommu replay callback for s390 pci iommu memory regi= on. >>>> Currently we don't need any dma mapping replay. So let it return >>>> directly. This implementation will avoid meaningless loops calling >>>> translation callback. >>>> >>>> Reviewed-by: Pierre Morel >>>> Reviewed-by: Halil Pasic >>>> Signed-off-by: Yi Min Zhao >>>> --- >>>> hw/s390x/s390-pci-bus.c | 8 ++++++++ >>>> 1 file changed, 8 insertions(+) >>>> >>>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c >>>> index 9e1f7ff5c5..359509ccea 100644 >>>> --- a/hw/s390x/s390-pci-bus.c >>>> +++ b/hw/s390x/s390-pci-bus.c >>>> @@ -407,6 +407,13 @@ static IOMMUTLBEntry s390_translate_iommu(IOMMU= MemoryRegion *mr, hwaddr addr, >>>> return ret; >>>> } >>>> =20 >>>> +static void s390_pci_iommu_replay(IOMMUMemoryRegion *iommu, >>>> + IOMMUNotifier *notifier) >>>> +{ >>>> + /* we don't need iommu replay currently */ >>> This really needs to be heavier on the _why_. My guess is that anythi= ng >>> which would require replay goes through the rpcit instruction? >> My understanding is: >> Our arch is different from others. Each pci device has its own iommu, = not >> like other archs' implementation. So currently there must be no existi= ng >> mappings belonging to any newly plugged pci device whose iommu doesn't >> have any mapping at the time. > So please put that explanation into the function. (Also, "currently"? > Are we expecting it to change?) The iommu replay function is originally introduced for vfio. I think=20 they want to re-build the existing mappings because vfio has a copy of mappings in kernel. For=20 our case, the mappings would be cleanup when a pci device unplugged, and new mappin= gs would be created when a pci device plugged. I think replay only can=20 happen during vfio-pci device migration. > >> In addition, it's also due to vfio blocking migration. If vfio-pci sup= ports >> migration in future, we could implement iommu replay by that time. > That's not an argument: This is the base zpci support, it should not > depend on the supported devices and what they do. (What's the status of > virtio-pci, btw? Does it work with your patches applied, or is there > still more to be done?) > > My understanding is virtio-pci doesn't need replay. All mappings of any=20 pci device are existing in guest memory. Once the mappings is built, all of them could be migrated=20 along with the guest system. But I might misunderstand it. Please correct me.