From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:46395) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gjlzz-0000UI-Q0 for qemu-devel@nongnu.org; Wed, 16 Jan 2019 09:16:56 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gjlzx-0004eP-Ra for qemu-devel@nongnu.org; Wed, 16 Jan 2019 09:16:55 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:41844 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 1gjlzw-0004bX-0q for qemu-devel@nongnu.org; Wed, 16 Jan 2019 09:16:53 -0500 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id x0GEAXdH057668 for ; Wed, 16 Jan 2019 09:16:50 -0500 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0b-001b2d01.pphosted.com with ESMTP id 2q23br894q-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 16 Jan 2019 09:16:50 -0500 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 16 Jan 2019 14:16:48 -0000 Reply-To: pmorel@linux.ibm.com References: <1547125207-16907-1-git-send-email-pmorel@linux.ibm.com> <1547125207-16907-2-git-send-email-pmorel@linux.ibm.com> <20190116134011.1189b027@oc2783563651> From: Pierre Morel Date: Wed, 16 Jan 2019 15:16:44 +0100 MIME-Version: 1.0 In-Reply-To: <20190116134011.1189b027@oc2783563651> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Message-Id: <1188d21d-3603-c291-e69b-38d341ae90f4@linux.ibm.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v2] s390x/pci: Set the iommu region size mpcifc request List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Halil Pasic , Collin Walling Cc: thuth@redhat.com, david@redhat.com, cohuck@redhat.com, qemu-devel@nongnu.org, borntraeger@de.ibm.com, qemu-s390x@nongnu.org, rth@twiddle.net On 16/01/2019 13:40, Halil Pasic wrote: > On Tue, 15 Jan 2019 10:35:42 -0500 > Collin Walling wrote: >=20 >> On 1/10/19 8:00 AM, Pierre Morel wrote: >>> The size of the accessible iommu memory region in the guest >>> is given to the IOMMU by the guest through the mpcifc request >>> specifying the PCI Base Address and the PCI Address Limit. >>> >>> Let set the size of the IOMMU region to: >>> (PCI Address Limit) - (PCI Base Address) + 1. >>> >>> Signed-off-by: Pierre Morel >>> --- >>> hw/s390x/s390-pci-bus.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c >>> index 69e0671..e97696a 100644 >>> --- a/hw/s390x/s390-pci-bus.c >>> +++ b/hw/s390x/s390-pci-bus.c >>> @@ -660,7 +660,7 @@ void s390_pci_iommu_enable(S390PCIIOMMU *iommu) >>> char *name =3D g_strdup_printf("iommu-s390-%04x", iommu->pbdev= ->uid); >>> memory_region_init_iommu(&iommu->iommu_mr, sizeof(iommu->iommu= _mr), >>> TYPE_S390_IOMMU_MEMORY_REGION, OBJECT= (&iommu->mr), >>> - name, iommu->pal + 1); >>> + name, iommu->pal - iommu->pba + 1); >=20 > From the the look of this, I would say we basically used the address > denoting the end of the region as the size of the region. This smells > like a bug to me, but the commit message and the title ain't clear abou= t > this, and there is no fixes tag. Because of the latter I did some diggi= ng > and came to commit f7c40aa "s390x/pci: fix failures of dma > map/unmap" (Yi Min Zhao, 2016-06-19) which basically did the inverse of > this commit! >=20 > My initial motivation was to check if this is stable material. But now > I'm very confused. I'm admittedly zPCI incompetent. Could some of the > people that understand what is going on help me feel better about this > patch? >=20 > Regards, > Halil The patch you speak about corrected the problem described in its comment=20 by setting the offset address of the subregion to 0, making sure=20 VFIO_PCI works for Z but introduced a bug we did not see at that time by=20 making the subregion too large. This patch correct the bug, I can add a reference to this with: fixing: commit f7c40aa1e7feb50bc4d4bc171fa811bdd9a93e51 Regards, Pierre >=20 >=20 >=20 >>> iommu->enabled =3D true; >>> memory_region_add_subregion(&iommu->mr, 0, MEMORY_REGION(&iomm= u->iommu_mr)); >>> g_free(name); >>> >> >> Acked-by: Collin Walling >> >> >=20 --=20 Pierre Morel Linux/KVM/QEMU in B=C3=B6blingen - Germany