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Tue, 4 Aug 2026 13:39:40 +0000 (GMT) Received: from [9.61.86.222] (unknown [9.61.86.222]) by smtpav02.dal12v.mail.ibm.com (Postfix) with ESMTP; Tue, 4 Aug 2026 13:39:37 +0000 (GMT) Message-ID: Date: Tue, 4 Aug 2026 09:39:24 -0400 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] vfio/pci: Avoid mapping BARs for devices with non-mappable BARs To: Farhan Ali , Alex Williamson Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, borntraeger@linux.ibm.com, mattev@meta.com, schnelle@linux.ibm.com References: <20260729181116.1373-1-alifm@linux.ibm.com> <46fede14-a740-4d66-98b3-c840e03e8634@linux.ibm.com> <20260729143603.175f60a7@shazbot.org> <42a3b06d-ecaa-4339-9472-7c592694f877@linux.ibm.com> <20260729155021.64f7e1ba@shazbot.org> <20260803135415.2cfd37bb@shazbot.org> From: Matthew Rosato Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: i70RW7y-2qvIFReZSmXt0wXht5mFqGuU X-Proofpoint-ORIG-GUID: i70RW7y-2qvIFReZSmXt0wXht5mFqGuU X-Proofpoint-Spam-Info: AW1haW4tMjYwODA0MDEwNyBTYWx0ZWRfXwUsYpUslVs5T 3WMZxIBu1O3PNk8O1wNUMxkcejei60U3ygznvPlxmDIlyANkgrdLzOJXduxHXbmicZjryi2TM9b YxFBmB2L7rPFIizvjAbMCwXMLbcfGOM= X-Authority-Analysis: v=2.4 cv=K8cS2SWI c=1 sm=1 tr=0 ts=6a71ebbe cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=mCxOg_z8nsbM3u4HIs0A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODA0MDEwNyBTYWx0ZWRfX+5lEBSaV6JdY i7eCL25pKPXd8ZboZ+nQjk0ZysYbvyUCG85BggWyf3hLg9Q6EaHUkw0Pgx1osK20d4AVEW66Yi8 mqL2QUgVcVnk9iUb4PFu6KMCWsiNXle/wEpZWTYA76H67J1OeO0CaiKQDRkArjewu55E8bUV7F6 JK6DLTEjuUKhN4pPVVE7L5pQRULAnbf9t10e0U2C9zn/BJwGIHDzU5VdYCjmBShqM6Vi+0Q/8mf nZSlozxl7jBjmQw/ttARBoM3HgPkTmJoOR2aTZzIMPYWObHTiqB0k2kcMVt0IGVvBUCeUmnf9Ja yd3Du10UWz2m7YPBTKwjtXYKzMUEevJs4nexZCHm14Jca8O/BmEy1oTbAk4d+/P0ihs0vxoXZrj oFU8HG61YsbTRCsbsfj5pJGwmckAZkwgbeX3yMwVs5WZmc5fv9gAFcUwhMqDZ8QLbFMd6VpG1BY HmaFeaF4O9Y3FR89WtA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-04_03,2026-08-03_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 spamscore=0 impostorscore=0 bulkscore=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0 phishscore=0 suspectscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608040107 >> The bar_mmap_supported flag describes something else, whether the BAR >> can be mapped into the user address space.  My intention was only to >> point out that there are BARs that cannot be mapped to the user address >> space because either they're not MMIO or we can't safely map the full >> page, therefore bar_mmap_supported is an invalid test for whether we >> should request the region or iomap the BAR. >> >> Is there still a gap with the original proposal that I'm missing? > > AFAICT this fix should be sufficient. I think Matt's question was to see > if there were other cases for which bar_mmap_supported were set to > false, that we need to consider here. But I will let him clarify to see > if he has any concerns. ^ Yes exactly that. To be clear: I am happy from the s390 side with the fix as it is proposed. My questions were basically trying to generate the conversation that was just had in an effort to avoid another fix later. So, with the context provided (thanks!): Reviewed-by: Matthew Rosato