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[209.85.221.43]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a7dc9ec8ce3sm500302566b.216.2024.08.05.17.19.16 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 05 Aug 2024 17:19:16 -0700 (PDT) Received: by mail-wr1-f43.google.com with SMTP id ffacd0b85a97d-3687f91af40so31009f8f.0 for ; Mon, 05 Aug 2024 17:19:16 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCWyNogZvmJ9ZSPCWh2RmgJ+9+vx7E5+Pz15487ByisrP2Efgh5uLcN6E0D6Kl05hTKKe2gtKMdct7afZvwvfGlQdO4= X-Received: by 2002:aa7:cd69:0:b0:58c:804a:6ee2 with SMTP id 4fb4d7f45d1cf-5b7f4294a1emr9353286a12.20.1722903230289; Mon, 05 Aug 2024 17:13:50 -0700 (PDT) MIME-Version: 1.0 References: <202408041602.caa0372-oliver.sang@intel.com> In-Reply-To: From: Linus Torvalds Date: Mon, 5 Aug 2024 17:13:34 -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: Nicholas Piggin Cc: Jeff Xu , Michael Ellerman , 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-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 982DC140005 X-Stat-Signature: wnrcectztn1np5dmpmh65ieszrmoh6e5 X-HE-Tag: 1722903559-866275 X-HE-Meta: U2FsdGVkX18hVB9cfN2cCiBbeGECIaKgW9OjN7EE5qypm/5uouAvFvT3QSdj2yJ7vOldEv+GQJYlDdw/7tOfPHNQajUWg5bhIxcBkCM0Lcy1bDccLSKhrbP60tq16OdSt0qUeXsYUo7Ayy23YWs/g7foicFEFJKfAqFGAMuXizqG1ED2hZc6J9U7nQE1j/W8+YIxrtYK72MTb1nD5FyeY1ESv+pAE6pdJzlQgCPvwbbr9DAgmOiHsx5/fKpCIpjCN1kJhACOP/0sF2Km9swvnYQcL1mpaXPnDRZubTN+A6Qp2yAohvqT4/oSdT8/+XeTuz4+E0A3ymOzscv+LUxZCCqg0Rrl7NvfAsTNoGJDAKPyayta2x5pZN3g3XuGlR8b2inZZdud7XHn2i2F0JCgs1o4bz0JAQLSlSIoWm5hvZoGpp5kvV/2FzjIkFeSfIHU13EPeZ9j0SMVmyd742GiZ7MDtYtAM6PQBU30hu8TOO0/zWdVU/L7y7g2WU1ZkTYhWtwSGxERsCNQmRAJlAovUKgjl8UrbE3899B7iGC8WM0qIdxJdFPxnFmcpPWSouFVgZA6FPmifCCNlk8Iadn3f00PxyJCRlxPm5ne5zM9pephxorT5NPpG5VdA/bRaPzybWWN5q0DD5hJZVqX7345rAG0dU3jMguvl3TVglUUO/gmgCacR4iluinCvlEKngKhOl5/N3HV3FLmtEFEiTttLRERdnGiFjTEjIczsNHaht2yL2BRW86egT3uHikkSFAr8TGu55fH67YSmFi3YbJQsXtU6wRHZHO97Zskbrq9Kar13NDZOFmE6iPc9NUimIojM2T17hSnu4a/EDMBausNherx9KhJdq+HdPuWzTjxqa/1k0AV1n0kGBnheFISn50HyugI6bvkpNFtcSHNCqEz7mZnvkP0RvujVPTT/uLGoG2r8mSgJVgKH0EqK5UCPSStvVkhVKpd9HTJ+NvUe+4 OToHR7W5 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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 16:25, Nicholas Piggin wrote: > > Can userspace on other archs not unmap their vdsos? I think they can, and nobody cares. The "context.vdso" value stays at some stale value, and anybody who tries to use it will just fail. So what makes powerpc special is not "you can unmap the vdso", but "powerpc cares". I just don't quite know _why_ powerpc cares. Judging by the comments and a quick 'grep', the reason may be arch/powerpc/perf/callchain_32.c which seems to have some vdso knowledge. But x86 does something kind of like that at signal frame generation time, and doesn't care. I really think it's an issue of "if you screw with the vdso, you get to keep both broken pieces". Linus