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Mon, 10 Aug 2026 17:43:54 +0000 (GMT) Received: from [9.61.246.243] (unknown [9.61.246.243]) by smtpav05.dal12v.mail.ibm.com (Postfix) with ESMTP; Mon, 10 Aug 2026 17:43:54 +0000 (GMT) Message-ID: <5dff4b7b-5ef6-43a4-8a76-9cced648320f@linux.ibm.com> Date: Mon, 10 Aug 2026 10:43:54 -0700 Precedence: bulk X-Mailing-List: linux-s390@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: 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, Matthew Rosato 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> Content-Language: en-US From: Farhan Ali In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=AMtp2X5w c=1 sm=1 tr=0 ts=6a7a0ddd cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=IRYEI1eNHJbscK6QoB4A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: nImi17arpchZtXcbJbDmnhRbY-o-palk X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODEwMDE1MCBTYWx0ZWRfXwrOte3XQ0u97 R8zwoi8U/Z1CirxVfyoXtA2Amg9rKpNTBHkKztjWOFbwyjvjqKFl90emD4MsIgsuP6opSdIfza9 k+JeMS7mrO7Vb58cz+XQEE+ZhXPC4r+DWWr6wi3Nvd6Z84h/Cj93hZddo6SBGcj7I4HEa+d9c7k WN3zJKAM4y5Cu/ZFlfWvUfKYAxsxFgOPjzIDys8Jo6wgN3tT8XuEjDJZXqnV54V4m+FMcKqB1+0 SlXnTtD3KiOrNk5MnpfJBHJ5/qkLMwOPVQ0b74/XuSptxorzilotF3yAu8c1PbNq6vZXKN0D6Mi XKCRT1szv1U9zl1dnwE4WQZOBnhLhPvZh9jXwQkqV9cuou4VOAfBTz8323xRiG52U/Hkbi4GTU/ G2v6uTSelK2+wD0mEeK9Z4cWk8w4oiArXhNidGuJOSDd7sIiTqOitoHPEoJh08t1qCBUbp0W+zg AzbbeG5wPwfhd/eNBIA== X-Proofpoint-ORIG-GUID: nImi17arpchZtXcbJbDmnhRbY-o-palk X-Proofpoint-Spam-Info: AW1haW4tMjYwODEwMDE1MCBTYWx0ZWRfX6IlODKmSqVdL f3jA7YSPSEdxWyB+cclbJesPDEQHBVjGyDATWf0Rma5NrjGn+EOfnG5NvVf6TGXPY6BTuhAuXdR CfG56N4uJafHDfjy0SV879uYNbPWKD4= 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=2026-08-10_04,2026-08-10_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 lowpriorityscore=0 clxscore=1015 priorityscore=1501 impostorscore=0 phishscore=0 spamscore=0 bulkscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608100150 On 8/4/2026 6:39 AM, Matthew Rosato wrote: >>> 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 Hi Alex, Polite ping on this patch. Please let me know if there are any other concerns with this patch or if we could consider this for inclusion to fix the regression on s390. Thanks Farhan