From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7DE03189B86 for ; Sun, 22 Dec 2024 11:16:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734866181; cv=none; b=Q8t/jBlCNdrVzkHrf4WJc/7qx5vcndnZhZ2J6sCmKxcMtTPqeIlBO/nOJkRTMChqNa+kMLoDbWI1n5xW9MCf/yAhGRRqLKVX+BuSkj5BJ9pQ00ciSAmZL551NIltthBI2EdgYESXo4pVeeldiSL/tUGjRoE4DwpZtq0HVfNP/SI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734866181; c=relaxed/simple; bh=OTdy2PDrtkZp0KGtgNaFNi7yjxFv/+ob2aKR7b/N9Mg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TXP8yutbFfn9vIhyqGDCOlWGNxvog0pJiM6dmBjtY5kGlS+CcpFRNkanDLNPheFAVH6Zj1W+HsiLYI0070DrDHyyZnKGH9UaWrFosn6N9w5F0GDQ/sVQ1z2Ugd+S0XfwAmasZ4EZq9W2U5vOQZxZ6x7J722ns4rNQcFXxn++njE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=JuQkdtv0; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="JuQkdtv0" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=lmhoSn2O9uahkkbEGigbjLHu3ZM8hxqe92Vn4y1ysHg=; b=JuQkdtv0jJ0x+2UrIcndeMs9ms ySSo4bpxfJftw9r5uy4nY+VpmQBgXTlHVEWQzm/Js1AVSAAUAogoq3C22TCLgTEMGBYsoOABIRsJ9 vxksmW5071QJXe0CCd5ytlQNHI06uO+Xr+ROQf8xdNFFnm4gMm4zsZOde0bJlals9HJloI+W8lQGN GvDmGgFzeF6yJnB78E+b38X9pH2OOUb2/blPi/DjQbJGjVg7WHB4eKU61RMU3lOSq0T4BHzVe4buz phuPkm8QzFH9wl3gNDU3UdvIEk4Nrs1hayfCmudmx5dg/wJ6P13nWUg8P6WZ+chR2HyoyeZ3Y9maP L74hnIIg==; Received: from 77-249-17-89.cable.dynamic.v4.ziggo.nl ([77.249.17.89] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tPJwM-000000066ic-2SDv; Sun, 22 Dec 2024 11:16:07 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 2E40A3003AF; Sun, 22 Dec 2024 12:16:06 +0100 (CET) Date: Sun, 22 Dec 2024 12:16:06 +0100 From: Peter Zijlstra To: Rik van Riel Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, dave.hansen@linux.intel.com, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, akpm@linux-foundation.org Subject: Re: [PATCH 04/10] x86,mm: use INVLPGB for kernel TLB flushes Message-ID: <20241222111606.GU11133@noisy.programming.kicks-ass.net> References: <20241222040717.3096835-1-riel@surriel.com> <20241222040717.3096835-5-riel@surriel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241222040717.3096835-5-riel@surriel.com> On Sat, Dec 21, 2024 at 11:06:36PM -0500, Rik van Riel wrote: > Use broadcast TLB invalidation for kernel addresses when available. > > This stops us from having to send IPIs for kernel TLB flushes. > > Signed-off-by: Rik van Riel > --- > arch/x86/mm/tlb.c | 32 ++++++++++++++++++++++++++++++++ > 1 file changed, 32 insertions(+) > > diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c > index 6cf881a942bb..09980fb17907 100644 > --- a/arch/x86/mm/tlb.c > +++ b/arch/x86/mm/tlb.c > @@ -1077,6 +1077,33 @@ void flush_tlb_all(void) > on_each_cpu(do_flush_tlb_all, NULL, 1); > } > > +static void broadcast_kernel_range_flush(unsigned long start, unsigned long end) > +{ > + unsigned long addr; > + unsigned long maxnr = boot_cpu_data.invlpgb_count_max; > + unsigned long threshold = tlb_single_page_flush_ceiling * maxnr; > + > + /* > + * TLBSYNC only waits for flushes originating on the same CPU. > + * Disabling migration allows us to wait on all flushes. > + */ > + migrate_disable(); So how expensive is all this? That is, I think I would feel better is this were preempt_disable(). > + > + if (end == TLB_FLUSH_ALL || > + (end - start) > threshold << PAGE_SHIFT) { > + invlpgb_flush_all(); > + } else { > + unsigned long nr; > + for (addr = start; addr < end; addr += nr << PAGE_SHIFT) { > + nr = min((end - addr) >> PAGE_SHIFT, maxnr); > + invlpgb_flush_addr(addr, nr); > + } > + } > + > + tlbsync(); > + migrate_enable(); > +} > + > static void do_kernel_range_flush(void *info) > { > struct flush_tlb_info *f = info; > @@ -1089,6 +1116,11 @@ static void do_kernel_range_flush(void *info) > > void flush_tlb_kernel_range(unsigned long start, unsigned long end) > { > + if (static_cpu_has(X86_FEATURE_INVLPGB)) { > + broadcast_kernel_range_flush(start, end); > + return; > + } > + > /* Balance as user space task's flush, a bit conservative */ > if (end == TLB_FLUSH_ALL || > (end - start) > tlb_single_page_flush_ceiling << PAGE_SHIFT) { > -- > 2.47.1 >