From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 32646C4320A for ; Mon, 2 Aug 2021 15:08:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 19AF9610FB for ; Mon, 2 Aug 2021 15:08:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234608AbhHBPIV (ORCPT ); Mon, 2 Aug 2021 11:08:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:60166 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234378AbhHBPIU (ORCPT ); Mon, 2 Aug 2021 11:08:20 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id EB99B60FF2; Mon, 2 Aug 2021 15:08:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627916890; bh=0vGZ83lRqAqx2M4uC9EaIbht4AZ9QFvE/a1NQzUEkB8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XgeHNzJW26UPbcfwvnVQS6WR/3QNF2+V2DMFU81S8hETWzi0vJwYLFPAwxH4wezao I0mkHsrP+3OnpGFvIHPomwtj99ODDeVowYmAOTubG/ivNQgC8XxCamDm41KNvim9j/ 9qnVK12FSYKhhg4zMrAa3FTp+PMXq/QR/nZANV6vYG2bn69J/iuzhejaVG0lytb39t TLlshtcEmyZZfU1BrmRCZy4FurOsnBMi8nOxxG5ypN5rj3t8XrgF0X1s0vE8/TqY2t CSQS3nwa0Vxo2gEbIw9hQr8QlvwJKS5Aj0uCSAlng6fAjRvKoZj9zKMnAg59nzB2Pl MBElQO33AHYLw== Date: Mon, 2 Aug 2021 18:08:02 +0300 From: Mike Rapoport To: Catalin Marinas Cc: Oleksandr Tyshchenko , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Oleksandr Tyshchenko , Will Deacon , Andrey Konovalov , Ard Biesheuvel , Vincenzo Frascino , Joey Gouly , Sami Tolvanen , Mark Rutland , Juergen Gross , Julien Grall , Wei Chen , Stefano Stabellini , Anshuman Khandual Subject: Re: [RFC PATCH 1/2] arm64: mm: Make virt_addr_valid to check for pfn_valid again Message-ID: References: <1627490656-1267-1-git-send-email-olekstysh@gmail.com> <20210802121947.GF18685@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210802121947.GF18685@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Mon, Aug 02, 2021 at 01:19:48PM +0100, Catalin Marinas wrote: > Adding Mike and Anshuman, > > On Wed, Jul 28, 2021 at 07:44:15PM +0300, Oleksandr Tyshchenko wrote: > > From: Oleksandr Tyshchenko > > > > The problem is that Arm's implementation of virt_addr_valid() > > leads to memblock_is_map_memory() check, which will fail for > > ZONE_DEVICE based addresses. But, the pfn_valid() check in turn > > is able to cope with ZONE_DEVICE based memory. > > > > You can find a good explanation of that problem at: > > https://lore.kernel.org/lkml/1614921898-4099-2-git-send-email-anshuman.khandual@arm.com > > > > Signed-off-by: Oleksandr Tyshchenko > > --- > > I am not quite sure whether it is a "correct" place and > > the change itself, I just partially restored a behaviour before: > > https://lore.kernel.org/lkml/20210511100550.28178-4-rppt@kernel.org > > So, the target of this patch is to get a feedback how to resolve > > this properly if, of course, this really needs to be resolved > > (I might miss important bits here). > > > > It is worth mentioning that patch doesn't fix the current code base > > (if I am not mistaken, no one calls virt_addr_valid() on Arm64 for > > ZONE_DEVICE based addresses at the moment, so it seems that nothing > > is broken), the fix is intended for the subsequent patch in this > > series that will try to enable Xen's "unpopulated-alloc" usage > > on Arm (it was enabled on x86 so far). > > Please see: > > [RFC PATCH 2/2] xen/unpopulated-alloc: Query hypervisor to provide > > unallocated space > > > > The subsequent patch will enable the code where virt_addr_valid() > > is used in drivers/xen/unpopulated-alloc.c:fill_list() to check that > > a virtual address returned by memremap_pages() is valid. > I wonder what the point of calling virt_addr_valid() in fill_list() is? > If memremap_pages() succeeded, the pages were mapped at the returned > vaddr, there's no need for an additional virt_addr_valid() check. The virt_addr_valid() check in fill_list() looks bogus to me as well. If memremap_pages() succeeds the range is guaranteed to have proper page table. I believe the first patch should be rather removal of the virt_addr_valid() check in fill_list(). > > --- > > arch/arm64/include/asm/memory.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h > > index 824a365..1a35a44 100644 > > --- a/arch/arm64/include/asm/memory.h > > +++ b/arch/arm64/include/asm/memory.h > > @@ -351,7 +351,7 @@ static inline void *phys_to_virt(phys_addr_t x) > > > > #define virt_addr_valid(addr) ({ \ > > __typeof__(addr) __addr = __tag_reset(addr); \ > > - __is_lm_address(__addr) && pfn_is_map_memory(virt_to_pfn(__addr)); \ > > + __is_lm_address(__addr) && pfn_valid(virt_to_pfn(__addr)); \ > > }) > > pfn_valid() only guarantees the presence of a struct page but not > necessarily that the virtual address is accessible (valid). So this > change would break the NOMAP ranges case. +1 -- Sincerely yours, Mike.