From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 9BED56B0253 for ; Fri, 8 Dec 2017 09:37:52 -0500 (EST) Received: by mail-pf0-f199.google.com with SMTP id u3so8958795pfl.5 for ; Fri, 08 Dec 2017 06:37:52 -0800 (PST) Received: from NAM03-BY2-obe.outbound.protection.outlook.com (mail-by2nam03on0067.outbound.protection.outlook.com. [104.47.42.67]) by mx.google.com with ESMTPS id d18si5594814pll.191.2017.12.08.06.37.50 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 08 Dec 2017 06:37:51 -0800 (PST) Subject: Re: [PATCH] x86/mm: Rewrite sme_populate_pgd() in a more sensible way References: <20171204112323.47019-1-kirill.shutemov@linux.intel.com> <20171204145755.6xu2w6a6og56rq5v@node.shutemov.name> <20171204163445.qt5dqcrrkilnhowz@black.fi.intel.com> <20171204173931.pjnmfdutys7cnesx@black.fi.intel.com> From: Tom Lendacky Message-ID: <55400fe3-a605-b86f-e14c-c5dd08738fd7@amd.com> Date: Fri, 8 Dec 2017 08:37:43 -0600 MIME-Version: 1.0 In-Reply-To: <20171204173931.pjnmfdutys7cnesx@black.fi.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Borislav Petkov , Brijesh Singh , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 12/4/2017 11:39 AM, Kirill A. Shutemov wrote: > On Mon, Dec 04, 2017 at 04:34:45PM +0000, Kirill A. Shutemov wrote: >> On Mon, Dec 04, 2017 at 04:00:26PM +0000, Tom Lendacky wrote: >>> On 12/4/2017 8:57 AM, Kirill A. Shutemov wrote: >>>> On Mon, Dec 04, 2017 at 08:19:11AM -0600, Tom Lendacky wrote: >>>>> On 12/4/2017 5:23 AM, Kirill A. Shutemov wrote: >>>>>> sme_populate_pgd() open-codes a lot of things that are not needed to be >>>>>> open-coded. >>>>>> >>>>>> Let's rewrite it in a more stream-lined way. >>>>>> >>>>>> This would also buy us boot-time switching between support between >>>>>> paging modes, when rest of the pieces will be upstream. >>>>> >>>>> Hi Kirill, >>>>> >>>>> Unfortunately, some of these can't be changed. The use of p4d_offset(), >>>>> pud_offset(), etc., use non-identity mapped virtual addresses which cause >>>>> failures at this point of the boot process. >>>> >>>> Wat? Virtual address is virtual address. p?d_offset() doesn't care about >>>> what mapping you're using. >>> >>> Yes it does. For example, pmd_offset() issues a pud_page_addr() call, >>> which does a __va() returning a non-identity mapped address (0xffff88...). >>> Only identity mapped virtual addresses have been setup at this point, so >>> the use of that virtual address panics the kernel. >> >> Stupid me. You are right. >> >> What about something like this: > > sme_pgtable_calc() also looks unnecessary complex. I have no objections to improving this (although I just submitted a patch that modifies this area, so this will have to be updated now). > > Any objections on this: > > diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c > index 65e0d68f863f..59b7d7ba9b37 100644 > --- a/arch/x86/mm/mem_encrypt.c > +++ b/arch/x86/mm/mem_encrypt.c > @@ -548,8 +548,7 @@ static void __init *sme_populate_pgd(pgd_t *pgd_base, void *pgtable_area, > > static unsigned long __init sme_pgtable_calc(unsigned long len) > { > - unsigned long p4d_size, pud_size, pmd_size; > - unsigned long total; > + unsigned long entries, tables; > > /* > * Perform a relatively simplistic calculation of the pagetable > @@ -559,41 +558,25 @@ static unsigned long __init sme_pgtable_calc(unsigned long len) > * mappings. Incrementing the count for each covers the case where > * the addresses cross entries. > */ > - if (IS_ENABLED(CONFIG_X86_5LEVEL)) { > - p4d_size = (ALIGN(len, PGDIR_SIZE) / PGDIR_SIZE) + 1; > - p4d_size *= sizeof(p4d_t) * PTRS_PER_P4D; > - pud_size = (ALIGN(len, P4D_SIZE) / P4D_SIZE) + 1; > - pud_size *= sizeof(pud_t) * PTRS_PER_PUD; > - } else { > - p4d_size = 0; > - pud_size = (ALIGN(len, PGDIR_SIZE) / PGDIR_SIZE) + 1; > - pud_size *= sizeof(pud_t) * PTRS_PER_PUD; > - } > - pmd_size = (ALIGN(len, PUD_SIZE) / PUD_SIZE) + 1; > - pmd_size *= sizeof(pmd_t) * PTRS_PER_PMD; > > - total = p4d_size + pud_size + pmd_size; > + entries = (DIV_ROUND_UP(len, PGDIR_SIZE) + 1) * PAGE_SIZE; I stayed away from using PAGE_SIZE directly because other areas/files used the sizeof() * PTRS_PER_ and I was trying to be consistent. Not that the size of a page table is ever likely to change, but maybe defining a macro (similar to the one in mm/pgtable.c) would be best rather than using PAGE_SIZE directly. Not required, just my opinion. > + if (PTRS_PER_P4D > 1) > + entries += (DIV_ROUND_UP(len, P4D_SIZE) + 1) * PAGE_SIZE; > + entries += (DIV_ROUND_UP(len, PUD_SIZE) + 1) * PAGE_SIZE; > + entries += (DIV_ROUND_UP(len, PMD_SIZE) + 1) * PAGE_SIZE; > > /* > * Now calculate the added pagetable structures needed to populate > * the new pagetables. > */ > - if (IS_ENABLED(CONFIG_X86_5LEVEL)) { > - p4d_size = ALIGN(total, PGDIR_SIZE) / PGDIR_SIZE; > - p4d_size *= sizeof(p4d_t) * PTRS_PER_P4D; > - pud_size = ALIGN(total, P4D_SIZE) / P4D_SIZE; > - pud_size *= sizeof(pud_t) * PTRS_PER_PUD; > - } else { > - p4d_size = 0; > - pud_size = ALIGN(total, PGDIR_SIZE) / PGDIR_SIZE; > - pud_size *= sizeof(pud_t) * PTRS_PER_PUD; > - } > - pmd_size = ALIGN(total, PUD_SIZE) / PUD_SIZE; > - pmd_size *= sizeof(pmd_t) * PTRS_PER_PMD; > > - total += p4d_size + pud_size + pmd_size; > + tables = DIV_ROUND_UP(entries, PGDIR_SIZE) * PAGE_SIZE; > + if (PTRS_PER_P4D > 1) > + tables += DIV_ROUND_UP(entries, P4D_SIZE) * PAGE_SIZE; > + tables += DIV_ROUND_UP(entries, PUD_SIZE) * PAGE_SIZE; > + tables += DIV_ROUND_UP(entries, PMD_SIZE) * PAGE_SIZE; > > - return total; > + return entries + tables; > } It all looks reasonable, but I won't be able to test for the next few days, though. Thanks, Tom > > void __init sme_encrypt_kernel(void) > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org