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Wed, 1 Jul 2026 08:35:28 +0000 (GMT) Message-ID: <1305d6eab67c4e7d751841a8894697ec851bd907.camel@linux.ibm.com> Subject: Re: [PATCH v5 2/4] s390/pci: Preserve FMB state in device re-enablement From: Niklas Schnelle To: Omar Elghoul , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, mjrosato@linux.ibm.com, alifm@linux.ibm.com, farman@linux.ibm.com, gbayer@linux.ibm.com, alex@shazbot.org In-Reply-To: <20260626175525.37370-3-oelghoul@linux.ibm.com> References: <20260626175525.37370-1-oelghoul@linux.ibm.com> <20260626175525.37370-3-oelghoul@linux.ibm.com> Autocrypt: addr=schnelle@linux.ibm.com; prefer-encrypt=mutual; keydata=mQINBGHm3M8BEAC+MIQkfoPIAKdjjk84OSQ8erd2OICj98+GdhMQpIjHXn/RJdCZLa58k /ay5x0xIHkWzx1JJOm4Lki7WEzRbYDexQEJP0xUia0U+4Yg7PJL4Dg/W4Ho28dRBROoJjgJSLSHwc 3/1pjpNlSaX/qg3ZM8+/EiSGc7uEPklLYu3gRGxcWV/944HdUyLcnjrZwCn2+gg9ncVJjsimS0ro/ 2wU2RPE4ju6NMBn5Go26sAj1owdYQQv9t0d71CmZS9Bh+2+cLjC7HvyTHKFxVGOznUL+j1a45VrVS XQ+nhTVjvgvXR84z10bOvLiwxJZ/00pwNi7uCdSYnZFLQ4S/JGMs4lhOiCGJhJ/9FR7JVw/1t1G9a UlqVp23AXwzbcoV2fxyE/CsVpHcyOWGDahGLcH7QeitN6cjltf9ymw2spBzpRnfFn80nVxgSYVG1d w75ksBAuQ/3e+oTQk4GAa2ShoNVsvR9GYn7rnsDN5pVILDhdPO3J2PGIXa5ipQnvwb3EHvPXyzakY tK50fBUPKk3XnkRwRYEbbPEB7YT+ccF/HioCryqDPWUivXF8qf6Jw5T1mhwukUV1i+QyJzJxGPh19 /N2/GK7/yS5wrt0Lwxzevc5g+jX8RyjzywOZGHTVu9KIQiG8Pqx33UxZvykjaqTMjo7kaAdGEkrHZ dVHqoPZwhCsgQARAQABtChOaWtsYXMgU2NobmVsbGUgPHNjaG5lbGxlQGxpbnV4LmlibS5jb20+iQ JXBBMBCABBAhsBBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAhkBFiEEnbAAstJ1IDCl9y3cr+Q/Fej CYJAFAmmAWs8FCQl6sYAACgkQr+Q/FejCYJAn2g//UKzlXOgizdk0wudLooRbGzDo23ktGSPK5Oj9 9o5z6v4Jz5+qOHo5835683cqkMLM9//udA1ZcKV88LVwyfmoHChPW24cWBmOEy7RJOWCR4WeEINaO pZUGF5YOx7oKTkPs511ky2FR0Heg35754pgTuTMEpYzRXr5pNMPS8mHXcXSARFPDPaCF+uBJ9BafO L7XbpSwKRttePsWAlPHbSbloeDApBfHUhcF/pbuM9GNs+c/8V9NK+SwwqNK214t7jaSq9k+19/hfE jvU45nbiYQM4VqGCelxVFRWol93JnwPFp/JaMgxgV1VYFH9Ijtgh+qNVVBqO8bbTjioFKy1bHdprN 9GyPLDxoaI/lBg+5CwKewzazUjFd0xaqZbTXSgNK4ev/IuNI3qZV8tpvZZWwIgZU1K0Bhplt8Sku+ O9Yl2H54erq9zuzwXjqBJtoW0+MaKbe+1gZ/v2/AVE2VeQMugPUWDg+2bpJaApRkeA4xQ9XfeW6Bp It7xYrwwbVhQtWRC0sRh+QNlU9HI28wPSnLWn7HFBeWupaIrxSp4IEL3eHUn8xv4aA8lpdNsHXD/X vqOSUwy5jlTPTlemvwaC9mNHagNdVXng8C6+hxiDLhZ6xH2P4qNHTKmjW61NsdF6Y/HfWP+lmbi8/ 474UNCltDt/fP01ajqogfWZKFymoH0O0KU5pa2xhcyBTY2huZWxsZSA8bmlrbGFzLnNjaG5lbGxlQ GlibS5jb20+iQJUBBMBCAA+AhsBBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAFiEEnbAAstJ1IDCl9y 3cr+Q/FejCYJAFAmmAWusFCQl6sYAACgkQr+Q/FejCYJAtIw//WmQW/Z+SLdfrlDH5J2bvixzFNnO TOvp8uM8vcNZsxZwPXem4AeCXHayCqipxpa0iXWufEIvdMxkBxWvvM//V+rTUgQnJe6nhDxfLGklx 5Mb2H+K/ndS73ElCuA30MPYq7mHr8i3gEmi2ZFX1W47JecJ8hno/DQxhHRG7bd+GFsiKCbsjLWXNq s/VaAK9uyOTQx7m6/2nR8L+Mvl1BrRXwkj7Qp0qxfQSd4r+IVNBzNFOcrGagBqsyHrN7Is7IICktH 9VFl/G8P+hfviHQLnlxw9ltzpM1Dy6N1+BM3kbqD59gX+L6wqiLJI42eh+SHCiy35FvD3AFlYx4jZ MWE6qIgFnbwcL1kvcA7nnwfr3ZizCYPm8e334xXxslXBoRGsvjXSbAeAyZo2dvJXffNHdcDdUbJSl CfOixNGGKiQvs00X9ekfq9WmmRFvmYHu/m3lg1OXnMjFFIO41O51ZdhbEYJiqZEki7jA8Hd9xuWwQ nFDHhacU3xxivZ4BKQGQc+4XZ3yp/q6+7ux9prepRy/LeRyoaAmE67oxEsAgj+qyA3Tfy5nRTDdRQ E//gpaIt9H1VEx+68dRWHroxBQeozpnFPi25AlX3k4/EtVZjcItPWgE9iru1qT4DH3BBrz7Kd1zUw NnQC77zDJyZD2WUj1E+5bftO0aeE+7HZXj3tM/ea0K05pa2xhcyBTY2huZWxsZSA8bmlrbGFzLnNj aG5lbGxlQGdtYWlsLmNvbT6JAlQEEwEIAD4CGwEFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AWIQSds ACy0nUgMKX3Ldyv5D8V6MJgkAUCaYBa6wUJCXqxgAAKCRCv5D8V6MJgkF/TEACOY2kL4NGFIbWeM5 TUhatxqe8c3RT6jvNjq32CkvaK/cSZzBkS0smddyOzxt2WnsvMgkr9cM7P+CevoMwhT3e0lgQbqBD /vXZJjWKddC+iKXeqWkjMVcgCOsWNZ7PWEzRUT5X1AEFq2zzxQAQ/bCWEYNqIbHN4b6G1Wk+2Y598 +KypZ3FS0bwiItnPQOWzOOqJCGxDxaEUuXFx4ah8HtVdtIev8jPS/5uzQO9iG2vZQUWeMEYZtfMHW sbFWqo2A3lxB+KPzNIYFhul4Lyx1CwvKUAGSHOx7FZuc2xI5DYt/Wdh2QyKFYr7xVzv3uwJjeS1+3 6gvyB7DJaQuY+PziNPv4GPr5wy0cRkJ6Ps15fgC6y6wNwoNdNXKlwiuclIsBzJKa7A0pZMIfpCpIJ bEHP7oy3drBRAhIrBx7Lx1lyqqodDqc+ok5IQ5WcKG/TOrH732mTmJX6fxYTiCVxcU4WLJSNZbrZ/ pjF0AWXs7E+onAkQy6RLg/XU1iiU5QdMvug+fTA6TpPSUMdujWtGWUt3/4nC+69AVc8tXtRQTZ7gP t7uIcQFwPqUuJGS26vl0w/6dIABQAyU9acvE3adCZra+/PBKFZi/yxT1WgV1T2mexKSWwQgLcR57J Yp5oWnQRgi/S6fAoskIWkp9UVcfAQPY0p45NwO5cZR9/g06JZmyrQhTmlrbGFzIFNjaG5lbGxlIDx uaWtzQGtlcm5lbC5vcmc+iQJUBBMBCAA+AhsBBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAFiEEnbAA stJ1IDCl9y3cr+Q/FejCYJAFAmmAWusFCQl6sYAACgkQr+Q/FejCYJAz4A/9F+dMhzu7YonagL4qh WDz5IpRD4vzYKOBZ+qwYp1ugJz1BIUppN9i68HKoS4ARfgP97Sv9GpOy9g7L0lymH2MPF8hRPK0Yn 7DKIkeu/r28YWEoWfoVm5reC+gpxMgmxBz4JScE4f6xfa7+Nw0bbTDl+nxftJD7lf/dTiruNJsXph HQnZ5wPXmxeH6XVJikfpyrGe8iJZALbtHtjlx6Omu7NvRGikenB8trrWS5W0F60ZdbqH1HdmDDcrZ pDq6LtAARHK5tGRm0SK6sZpKe3nULFeeCt7T/edk2FC6KVh4sL1jw1kyceX4DjiMffqYBPrhK5gz5 cDIixLBF9C6Wt1ObvuDBrIQf1/3q6EZrUrUuf6qtaXDMuC6cSlShm47qaPEvVYh67O9JZQ7vzvaea UI74DJUb8Pjnz7mTOmMOzsS1gUhCue4n2YSSM6ythioCGb/3bgMGTpuer3JhvZG5s5uKD9yyj8s8x 35qJkCFfjmjVx9s3vSUS48X+cUpYcMispErKzFu7C0YgKoxvJ4XTfXlDBiMFMPYcN67hsb2jeYHVJ wzE+fIZiDx9JLh1oQW2krwjweisE+3glOaKXZKi0fBtkxyH41iemLtLNYZRJopv6ykdl3hiI+Nh+a 3FZJPTo/OpqchMm8XIeDxC4NFFiPMpyLeYzIxO7eZpiGrAjVTE= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Wed, 01 Jul 2026 10:34:27 +0200 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzAxMDA4NCBTYWx0ZWRfX11XgYzcjGvVq Rp5AbHHAu/r8uPt0lHYbD320Q/m+T7ugs23tnTXbTIojcJq2rU4ckMTuuRHqDrKfQEhWfnlrJPO 4nk726bxhU2xGWxbByXNxs0Y+6XLhh/4WKqRZZqfIuqP0kdbl07ALv6eLjny+5w2DzYeESoEgND 6NrICHAz7gDnkU5U/hMfspzVjLImQn1424I5/EfnqwPjmzXzkoAfBZCxdBU7CX1NdpADFCEb9TK xnXatEEypqkSpb5W5gbD5l93zF8N94ok+B1JdM8AJiFSEL9O2LN/r/Qo6+8LGfpSsXuX9Ouk0qC mmd4FUdluS5561drIezEv4DkoaL+H1ap83cxSZ+VwksjPukFK9sQWqbfe4b4SvQjoltT2im6eJc 9ja9fCCZw5lyMqy0RreReh9nvL5CDdBcBklx/e5mSIzwtlpWA1/6u++1CY+BDL0Z1oyGP7+A7Qc NMn3AZQyta69pFzBI6A== X-Proofpoint-Spam-Info: AW1haW4tMjYwNzAxMDA4NCBTYWx0ZWRfX59Hvaucl0uEJ GfomzBqyPOyTmQySm9GmJyhAaW6ZAR2EF16jLEBNKVnrAIo9sloVkmrKLsg+FG8UQQ3CLE3xAqH kahZVdyco8WWU4Bz6KlvRsY34LmrE7E= X-Proofpoint-GUID: EUXxwv_x_bh8ZAvDq6NPH6gYcasNrSai X-Proofpoint-ORIG-GUID: EUXxwv_x_bh8ZAvDq6NPH6gYcasNrSai X-Authority-Analysis: v=2.4 cv=WZ88rUhX c=1 sm=1 tr=0 ts=6a44d155 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=sgYR8afB-gvAtxywVdAA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-07-01_02,2026-06-26_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 adultscore=0 phishscore=0 clxscore=1015 bulkscore=0 impostorscore=0 priorityscore=1501 lowpriorityscore=0 suspectscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607010084 On Fri, 2026-06-26 at 13:55 -0400, Omar Elghoul wrote: > Introduce a function zpci_fmb_reenable_device() that checks the state of > the FMB and ensures it is enabled. Reset the counters to zero, disable, a= nd > re-enable the FMB if it was already enabled. Call this function during a > zPCI device re-enablement, which in turn implicitly ensures that the FMB = is > enabled for host devices during their KVM registration. >=20 > Signed-off-by: Omar Elghoul > --- Just to keep the list up to date. We're still discussing some details about this internally. Mostly about how this may interact with platform behavior in some edge cases that are likely not possible with current implementations but would be covered by the architecture.=C2=A0 Personally, I actually liked the re-using of the buffer in v4 better and I think depending on implementations of the kmem_cache, specifically if it may give us back the same buffer that we just freed in the immediately following allocation, this could also end up re- using the same buffer anyway. Hope to get the details sorted soon. Thanks, Niklas