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X-CSE-ConnectionGUID: /TFNbEk2QMWiHndKILF2Wg== X-CSE-MsgGUID: GKP+klqESjqwPch3qRJNVQ== X-IronPort-AV: E=McAfee;i="6700,10204,11359"; a="41829000" X-IronPort-AV: E=Sophos;i="6.13,323,1732608000"; d="scan'208";a="41829000" Received: from orviesa009.jf.intel.com ([10.64.159.149]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Feb 2025 11:00:39 -0800 X-CSE-ConnectionGUID: EBMu4hBbS/Crc4gtf7KobA== X-CSE-MsgGUID: /UwnTwopSteZ2ardV4z7pQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.13,323,1732608000"; d="scan'208";a="117172545" Received: from dwoodwor-mobl2.amr.corp.intel.com (HELO [10.125.108.137]) ([10.125.108.137]) by orviesa009-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Feb 2025 11:00:39 -0800 Message-ID: <4c2144a4-8889-483b-bb16-4d361d1d3d90@intel.com> Date: Fri, 28 Feb 2025 11:00:52 -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 04/13] x86/mm: use INVLPGB for kernel TLB flushes 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> <20250226030129.530345-5-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: > Use broadcast TLB invalidation for kernel addresses when available. > > Remove the need to send IPIs for kernel TLB flushes. Nit: the changelog doesn't address the refactoring. *Ideally*, you'd create the helpers and move the code there in one patch and then actually "use INVLPGB for kernel TLB flushes" in the next. It's compact enough here that it's not a deal breaker. > +static void invlpgb_kernel_range_flush(struct flush_tlb_info *info) > +{ > + unsigned long addr, nr; > + > + for (addr = info->start; addr < info->end; addr += nr << PAGE_SHIFT) { > + nr = (info->end - addr) >> PAGE_SHIFT; > + nr = clamp_val(nr, 1, invlpgb_count_max); > + invlpgb_flush_addr_nosync(addr, nr); > + } > + __tlbsync(); > +} This needs a comment or two. Explaining that the function can take large sizes: /* * Flush an arbitrarily large range of memory with INVLPGB */ But that the _instruction_ can not is important. This would be great in the loop just above the clamp: /* * INVLPGB has a limit on the size of ranges * it can flush. Break large flushes up. */ > static void do_kernel_range_flush(void *info) > { > struct flush_tlb_info *f = info; > @@ -1087,6 +1099,22 @@ static void do_kernel_range_flush(void *info) > flush_tlb_one_kernel(addr); > } > > +static void kernel_tlb_flush_all(struct flush_tlb_info *info) > +{ > + if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) > + invlpgb_flush_all(); > + else > + on_each_cpu(do_flush_tlb_all, NULL, 1); > +} > + > +static void kernel_tlb_flush_range(struct flush_tlb_info *info) > +{ > + if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) > + invlpgb_kernel_range_flush(info); > + else > + on_each_cpu(do_kernel_range_flush, info, 1); > +} > + > void flush_tlb_kernel_range(unsigned long start, unsigned long end) > { > struct flush_tlb_info *info; > @@ -1097,9 +1125,9 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end) > TLB_GENERATION_INVALID); > > if (info->end == TLB_FLUSH_ALL) > - on_each_cpu(do_flush_tlb_all, NULL, 1); > + kernel_tlb_flush_all(info); > else > - on_each_cpu(do_kernel_range_flush, info, 1); > + kernel_tlb_flush_range(info); > > put_flush_tlb_info(); > } But the structure of this code is much better than previous versions. With the comments fixed: Acked-by: Dave Hansen