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X-CSE-ConnectionGUID: maatvzuRSK23C0rJkrDdjA== X-CSE-MsgGUID: R+6UlVu3SDGE0q8osCfiIA== X-IronPort-AV: E=McAfee;i="6700,10204,11359"; a="41630393" X-IronPort-AV: E=Sophos;i="6.13,323,1732608000"; d="scan'208";a="41630393" Received: from fmviesa004.fm.intel.com ([10.60.135.144]) by orvoesa113.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Feb 2025 11:17:53 -0800 X-CSE-ConnectionGUID: vO1UPoHFT6SjOnZvHu1trA== X-CSE-MsgGUID: BOiTYdPwQaO5RF9WQKGJ1Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.13,323,1732608000"; d="scan'208";a="122553982" Received: from dwoodwor-mobl2.amr.corp.intel.com (HELO [10.125.108.137]) ([10.125.108.137]) by fmviesa004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Feb 2025 11:17:52 -0800 Message-ID: Date: Fri, 28 Feb 2025 11:18:04 -0800 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 v14 05/13] x86/mm: use INVLPGB in flush_tlb_all To: Rik van Riel , x86@kernel.org Cc: linux-kernel@vger.kernel.org, bp@alien8.de, peterz@infradead.org, dave.hansen@linux.intel.com, zhengqi.arch@bytedance.com, nadav.amit@gmail.com, thomas.lendacky@amd.com, kernel-team@meta.com, linux-mm@kvack.org, akpm@linux-foundation.org, jackmanb@google.com, jannh@google.com, mhklinux@outlook.com, andrew.cooper3@citrix.com, Manali.Shukla@amd.com, mingo@kernel.org References: <20250226030129.530345-1-riel@surriel.com> <20250226030129.530345-6-riel@surriel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/25/25 19:00, Rik van Riel wrote: > void flush_tlb_all(void) > { > count_vm_tlb_event(NR_TLB_REMOTE_FLUSH); > + > + /* First try (faster) hardware-assisted TLB invalidation. */ > + if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) { > + guard(preempt)(); > + invlpgb_flush_all(); > + return; > + } We haven't talked at all about the locking rules for invlpgb_flush_all(). It was used once in this series without any explicit preempt twiddling. I assume that was because it was used in a path where preempt is disabled. If it does need a universal rule about preempt, can we please add an: lockdep_assert_preemption_disabled() along with a comment about why it needs preempt disabled? Also, the previous code did: if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) invlpgb_foo(); else old_foo(); Is there a reason to break with that pattern? It would be nice to be consistent.