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Tue, 28 Oct 2025 14:14:46 -0700 (PDT) Received: from [192.168.2.110] ([70.49.125.126]) by smtp.gmail.com with ESMTPSA id af79cd13be357-89f254a297dsm929505785a.28.2025.10.28.14.14.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Oct 2025 14:14:46 -0700 (PDT) Message-ID: <5cc06269-5a6e-4874-bf68-fa4790f22bc2@redhat.com> Date: Tue, 28 Oct 2025 17:14:35 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: hugetlb: fix HVO crash on s390 To: Heiko Carstens 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 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> <20251028193708.7213A7e-hca@linux.ibm.com> Content-Language: en-US, en-CA From: Luiz Capitulino In-Reply-To: <20251028193708.7213A7e-hca@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025-10-28 15:37, Heiko Carstens wrote: > 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. Exactly. I'll also see if I can find time to explore your API improvement suggestion. I'll send v2 shortly.