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[209.85.208.50]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5b8396114bcsm5482449a12.6.2024.08.05.19.15.49 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 05 Aug 2024 19:15:50 -0700 (PDT) Received: by mail-ed1-f50.google.com with SMTP id 4fb4d7f45d1cf-5bb477e3a6dso58074a12.0 for ; Mon, 05 Aug 2024 19:15:49 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCXFAD5LBDtmv44peM+aGv9hzhMhTohFEba2wWMPDbRLqbYw+EU6QfgPNR3Y4aeiFI7hwRfwG3nQrJd4RoZx4JkY5/Q= X-Received: by 2002:aa7:cb43:0:b0:5aa:19b1:ffde with SMTP id 4fb4d7f45d1cf-5b7f59e20a8mr9459334a12.34.1722910549350; Mon, 05 Aug 2024 19:15:49 -0700 (PDT) MIME-Version: 1.0 References: <202408041602.caa0372-oliver.sang@intel.com> <87r0b2if4t.fsf@mail.lhotse> In-Reply-To: <87r0b2if4t.fsf@mail.lhotse> From: Linus Torvalds Date: Mon, 5 Aug 2024 19:15:32 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [linus:master] [mseal] 8be7258aad: stress-ng.pagemove.page_remaps_per_sec -4.4% regression To: Michael Ellerman Cc: Nicholas Piggin , Jeff Xu , Christophe Leroy , Pedro Falcato , kernel test robot , Jeff Xu , oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, Andrew Morton , Kees Cook , "Liam R. Howlett" , Dave Hansen , Greg Kroah-Hartman , Guenter Roeck , Jann Horn , Jonathan Corbet , Jorge Lucangeli Obes , Matthew Wilcox , Muhammad Usama Anjum , =?UTF-8?Q?Stephen_R=C3=B6ttger?= , Suren Baghdasaryan , Amer Al Shanawany , Javier Carrasco , Shuah Khan , linux-api@vger.kernel.org, linux-mm@kvack.org, ying.huang@intel.com, feng.tang@intel.com, fengwei.yin@intel.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: C357740018 X-Stat-Signature: g59s5fxujj3csd73bu8bw8hsbd8osnc1 X-Rspam-User: X-HE-Tag: 1722910552-356850 X-HE-Meta: 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 msG0COtx 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 5 Aug 2024 at 19:01, Michael Ellerman wrote: > > > > > I just don't quite know _why_ powerpc cares. > > AFAIK for CRIU the problem is signal delivery: Hmm. Well, the patch I sent out should keep it all working. In fact, to some degree it would make it much more straightforward for other architectures to do the same thing. Instead of a random "arch_munmap()" hack, it's a fairly reasonable _install_special_mapping() extension. That said, the *other* thing I don't really understand is the strange "we have to set the context.vdso value before calling install_special_mapping": /* * Put vDSO base into mm struct. We need to do this before calling * install_special_mapping or the perf counter mmap tracking code * will fail to recognise it as a vDSO. */ and that looks odd too. Anyway, I wish we could just get rid of all the horrible signal restore crap. We used to just put it in the stack, and that worked really well apart from the whole WX thing. I wonder if we should just go back to that, and turn the resulting "page fault due to non-executable stack" into a "sigreturn system call". And yes, SA_RESTORER is the right thing. It's basically just user space telling us where it is. And happily, on x86-64 we just forced the issue, and we do /* x86-64 should always use SA_RESTORER. */ if (!(ksig->ka.sa.sa_flags & SA_RESTORER)) return -EFAULT; so you literally cannot have signals without it. Linus