From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f178.google.com (mail-pl1-f178.google.com [209.85.214.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D8DC51B0439 for ; Tue, 18 Feb 2025 05:27:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739856458; cv=none; b=Hf5MF40LWPHIKnt5LNw8yyE6Hkx54P0Gd+aGDL5hEKTx8M4qQp28m5IstKwM4yfrSm2PVYg+Dubq3Co6x/JQQmhpM7ZdyvXg6mlSjTfqirE4W7CUcVQ9PfFLXGceouh11aL6C3FgYyx97CtZAk58o3l4TnOVV9kF1Y+Y0UtGWeg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739856458; c=relaxed/simple; bh=+9uCyGXOAJ0ZSD5E3hkk/2H2EZqIk3JHrGCiuf0AfgE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WvdMbWEjgkisvf5ZJJC7Nc/tUYOsLfWUX7a8kpC1fyuq1wnEzbTNfmKNSFwPPjOiUWXLu8YFz5ldyo4n9hPd4acl3K5c2bejvt/ly6EjJVDN9yl0DoMhMiPXoicS3uxtdYXQgCBqu7SxXvCgs4m1CX6IlTYMgG7FY27UqDN1REg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=KP5IbQr2; arc=none smtp.client-ip=209.85.214.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="KP5IbQr2" Received: by mail-pl1-f178.google.com with SMTP id d9443c01a7336-22100006bc8so48496505ad.0 for ; Mon, 17 Feb 2025 21:27:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1739856456; x=1740461256; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=HxqZOLsj7jsOonVVaVaqp826M8Lpw89ZMq77OrIZj20=; b=KP5IbQr2NZvlCvlF1gFqjwdPfHrhNId3+nQKw0vn76P/YcPWXA7iJW8Q9eke1W4Js9 zGDUI11dAK/YzywzzQhiZNn+2kDaZ+rBSVyBSlmUsk3vbnf4koxpEu38OS3nlHmPIO77 mkn2/dIHy5arkyXRNO/y1K1YGTJXnbx25zDQD1ZG7pT7Hkew+ax3iXYn7U2JdnnqkKRR fsRVmD70wsQDcCDIn46DBWCgudNH3PFljq0AZVg1AG3WBRrJzuSKRNzvxf+z/e7nPFP2 O/+xdJimk12XQtRAWzmj1NeNhhgB8SEYB7Dc9sexo6hZdv62pfE8tnVaYZEoHhYoXwC7 kAZw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1739856456; x=1740461256; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=HxqZOLsj7jsOonVVaVaqp826M8Lpw89ZMq77OrIZj20=; b=nLqgbKdPOcKLuDXqG1pSm0bYoC+1l01GVYRMPYF9GykXM9d2TxIfhAcYKGzAoQdA3S 6bEf8Dg+IBtmuPwvBEn2D9DsVnP056ZjItteCCEqZsaiblTQkgWhrxcqjb4L+EPtHFlp Hbm4a301a6T7c33gjO6Auf2fz1MERfBd8BWQUdTynDGCyjnKQzB54DgRAVOtCZDKA47V KxJtxDru1wo6QZmKq5PsVQ+SP8SxBU/5oQgQtIVq0j8LnFih3caLuiQ4FSJ/vIqw+URM VyLt/65BmcxyrxjIfvGkmJlwMpyUnUv41KpNUuTUZwQn+7pJD17BJxb0MP4v7cCMw3Dz blTA== X-Gm-Message-State: AOJu0YwFmy1Dp6fOBAx15X9IZe7ojB3O0vG20nuAe2iSn9CrSyvqTK5S MW5Z7kcpvQ+f3uGSREQZb/VDp0usQ2wJk/JtMHlycHSVA0FXPcYZ X-Gm-Gg: ASbGncuMy8/3WI/4Wa7Ko/JsH65PkLB3Z2wl0dWpKtmrCZR3uS3AXhD99S2rpQK88hP XvuWcEzLmJrkBBSWl3lHRxwZf0BjMNIuZzNCJXo96zAH7uWlZ8D2JOgUhiRSHciIsyfBzpL9o9/ XTbNyMgt71UYg9kWPAbx8I8KYCXtNR3wXZAEsnAaVA/khZFvKjEL+DCFOwLhXPwEgWjKTllKo9Z ULexMfunn9vJzDeF8i30KvKsS1rcMtl21iJI/5JShCB3o7p3NFFgYvRFV9iOXKX3KPeizpEfQ22 T9VxWP+mmnFmR8qjjIgu1thKnh6UbLSUQD2WozD20KZCiFI= X-Google-Smtp-Source: AGHT+IF5VyxzzJu90hZ1mhaq1UwHE6K8UC73LdsXtYWXKAJmnEPRpcOlHz7oLZrH6QhnpDCgjbTr1A== X-Received: by 2002:a17:903:1ce:b0:220:cd61:c03b with SMTP id d9443c01a7336-2210404bf14mr167296225ad.21.1739856455858; Mon, 17 Feb 2025 21:27:35 -0800 (PST) Received: from MacBook-Air-5.local ([2001:2d8:f03b:2a87:480c:6184:1db1:ca0b]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-220d545d453sm79029535ad.115.2025.02.17.21.27.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Feb 2025 21:27:35 -0800 (PST) Date: Tue, 18 Feb 2025 14:27:27 +0900 From: "Harry Yoo (Oracle)" <42.hyeyoo@gmail.com> To: Gwan-gyeong Mun Cc: linux-kernel@vger.kernel.org, osalvador@suse.de, byungchul@sk.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, akpm@linux-foundation.org, max.byungchul.park@sk.com, max.byungchul.park@gmail.com Subject: Re: [PATCH 1/1] x86/vmemmap: Use direct-mapped VA instead of vmemmap-based VA Message-ID: References: <20250217114133.400063-1-gwan-gyeong.mun@intel.com> <20250217114133.400063-2-gwan-gyeong.mun@intel.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: <20250217114133.400063-2-gwan-gyeong.mun@intel.com> On Mon, Feb 17, 2025 at 01:41:33PM +0200, Gwan-gyeong Mun wrote: > When a process leads the addition of a struct page to vmemmap > (e.g. hot-plug), the page table update for the newly added vmemmap-based > virtual address is updated first in init_mm's page table and then > synchronized later. > > If the vmemmap-based virtual address is accessed through the process's > page table before this sync, a page fault will occur. > > This translates vmemmap-based virtual address to direct-mapped virtual > address and use it, if the current top-level page table is not init_mm's > page table when accessing a vmemmap-based virtual address before this sync. > > Fixes: faf1c0008a33 ("x86/vmemmap: optimize for consecutive sections in partial populated PMDs") > Signed-off-by: Gwan-gyeong Mun > Cc: Oscar Salvador > Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> I think this fix is reasonable without changing existing code too much. Any thoughts from x86 folks? > Cc: Byungchul Park > Cc: Dave Hansen > Cc: Andy Lutomirski > Cc: Peter Zijlstra > Cc: Andrew Morton Shouldn't we add Cc: ? -- Harry > --- > arch/x86/mm/init_64.c | 17 ++++++++++++++--- > 1 file changed, 14 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c > index 01ea7c6df303..1cb26f692831 100644 > --- a/arch/x86/mm/init_64.c > +++ b/arch/x86/mm/init_64.c > @@ -844,6 +844,17 @@ void __init paging_init(void) > */ > static unsigned long unused_pmd_start __meminitdata; > > +static void * __meminit vmemmap_va_to_kaddr(unsigned long vmemmap_va) > +{ > + void *kaddr = (void *)vmemmap_va; > + pgd_t *pgd = __va(read_cr3_pa()); > + > + if (init_mm.pgd != pgd) > + kaddr = __va(slow_virt_to_phys(kaddr)); > + > + return kaddr; > +} > + > static void __meminit vmemmap_flush_unused_pmd(void) > { > if (!unused_pmd_start) > @@ -851,7 +862,7 @@ static void __meminit vmemmap_flush_unused_pmd(void) > /* > * Clears (unused_pmd_start, PMD_END] > */ > - memset((void *)unused_pmd_start, PAGE_UNUSED, > + memset(vmemmap_va_to_kaddr(unused_pmd_start), PAGE_UNUSED, > ALIGN(unused_pmd_start, PMD_SIZE) - unused_pmd_start); > unused_pmd_start = 0; > } > @@ -882,7 +893,7 @@ static void __meminit __vmemmap_use_sub_pmd(unsigned long start) > * case the first memmap never gets initialized e.g., because the memory > * block never gets onlined). > */ > - memset((void *)start, 0, sizeof(struct page)); > + memset(vmemmap_va_to_kaddr(start), 0, sizeof(struct page)); > } > > static void __meminit vmemmap_use_sub_pmd(unsigned long start, unsigned long end) > @@ -924,7 +935,7 @@ static void __meminit vmemmap_use_new_sub_pmd(unsigned long start, unsigned long > * Mark with PAGE_UNUSED the unused parts of the new memmap range > */ > if (!IS_ALIGNED(start, PMD_SIZE)) > - memset((void *)page, PAGE_UNUSED, start - page); > + memset(vmemmap_va_to_kaddr(page), PAGE_UNUSED, start - page); > > /* > * We want to avoid memset(PAGE_UNUSED) when populating the vmemmap of > -- > 2.48.1 >