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Tue, 28 Oct 2025 19:37:09 +0000 (GMT) Date: Tue, 28 Oct 2025 20:37:08 +0100 From: Heiko Carstens To: Luiz Capitulino Cc: Joao Martins , osalvador@suse.de, akpm@linux-foundation.org, david@redhat.com, aneesh.kumar@kernel.org, borntraeger@linux.ibm.com, mike.kravetz@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, Vasily Gorbik , Gerald Schaefer , Alexander Gordeev Subject: Re: [PATCH] mm: hugetlb: fix HVO crash on s390 Message-ID: <20251028193708.7213A7e-hca@linux.ibm.com> References: <20251028153930.37107-1-luizcap@redhat.com> <50d815a1-8384-4eaa-8515-19d6c92425b3@oracle.com> <20251028161426.35377Af6-hca@linux.ibm.com> <5c72e064-9298-490e-b05a-16be6b5590b7@oracle.com> <20251028170251.11688Aa3-hca@linux.ibm.com> <4f522b65-1ab8-4725-8da7-3f071e7919c1@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4f522b65-1ab8-4725-8da7-3f071e7919c1@redhat.com> X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=fIQ0HJae c=1 sm=1 tr=0 ts=69011b6b cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=kj9zAlcOel0A:10 a=x6icFKpwvdMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=f0Pcmk6uCRRijeZF_SEA:9 a=CjuIK1q_8ugA:10 a=cPQSjfK2_nFv0Q5t_7PE:22 X-Proofpoint-ORIG-GUID: ZIIeRTfL90xSM42Fi60shxNf7BZy0dhp X-Proofpoint-GUID: ZIIeRTfL90xSM42Fi60shxNf7BZy0dhp X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDI1MDAyNCBTYWx0ZWRfX7+qngpRd+nhm /sp757299cAtgUe4mlSUay8+yRs9JiuYNSihUWaB9g8OQ4lFb7tsSQdGTqjgjMLApRrCiEOb75y FYXLVxaAgLS2Qm/kMkQJpZ2viAOH+ODIGJkVMF5N7K6XvLxiYJB2vH+Gnv7Pp6S96aOoujozU0U Xm4Q1WeAAYDaODGNh4T6MfV66OVPP8Dnu4nwpdf+SL+29TmLrAz7TvmcZWQ/Y/2xlwmKLUiar8K bb47GRSkWpc9qIAXETDyv6QGlZwJGkxIDUq9+4EZJKMgSjCrRpuTRf1RX4HujpDdjs6RTm6UngO sEamq2O4vHD3ikBMncC8glIbvdbfixV5MIKMPw1hPgzGRQae4USiv1Xyb0U4xx/C+LiLt3WbRYU fygbAbHeYtGxx22TffGyBpoH3QgoEA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-10-28_07,2025-10-22_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 priorityscore=1501 adultscore=0 suspectscore=0 spamscore=0 clxscore=1015 bulkscore=0 lowpriorityscore=0 phishscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510020000 definitions=main-2510250024 On Tue, Oct 28, 2025 at 01:15:57PM -0400, Luiz Capitulino wrote: > > > flush_tlb_all() however is the *closest* equivalent to this that's behind an > > > arch generic API i.e. flushing kernel address space on all CPUs TLBs. IIUC, x86 > > > when doing flush_tlb_kernel_range with enough pages it switches to flush_tlb_all > > > (these days on modern AMDs it's even one instruction solely in the calling CPU). > > > > Considering that flush_tlb_all() should be mapped to __tlb_flush_global() > > and not __tlb_flush_kernel() on s390. > > You're right. > > > However if there is only a need to flush tlb entries for the complete(?) > > kernel address space, then I'd rather propose a new tlb_flush_kernel() > > instead of a big hammer. If I'm not mistaken flush_tlb_kernel_range() > > exists for just avoiding that. And if architectures can avoid a global > > flush of _all_ tlb entries then that should be made possible. > > Should we take a v2 doing your suggestion above for now and work on > the tlb_flush_kernel() idea as a follow up improvement? At least we > go from crashing to flushing more than we should... That's of course fine. I guess for stable backports a small fix is the best way forward anyway.