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Message-ID: <910adbb5-c5d7-3091-1c92-996f73dd6221@redhat.com>
Date: Mon, 14 Aug 2017 15:30:00 -0700
From: Laura Abbott <labbott@...hat.com>
To: Tycho Andersen <tycho@...ker.com>, linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, kernel-hardening@...ts.openwall.com,
Marco Benatto <marco.antonio.780@...il.com>,
Juerg Haefliger <juerg.haefliger@...onical.com>,
Juerg Haefliger <juerg.haefliger@....com>
Subject: Re: [PATCH v5 02/10] mm, x86: Add support for eXclusive Page Frame
Ownership (XPFO)
On 08/09/2017 01:07 PM, Tycho Andersen wrote:
> +/* Update a single kernel page table entry */
> +inline void set_kpte(void *kaddr, struct page *page, pgprot_t prot)
> +{
> + unsigned int level;
> + pgprot_t msk_clr;
> + pte_t *pte = lookup_address((unsigned long)kaddr, &level);
> +
> + BUG_ON(!pte);
> +
> + switch (level) {
> + case PG_LEVEL_4K:
> + set_pte_atomic(pte, pfn_pte(page_to_pfn(page), canon_pgprot(prot)));
> + break;
> + case PG_LEVEL_2M:
> + /* We need to check if it's a 2M page or 1GB page before retrieve
> + * pgprot info, as each one will be extracted from a different
> + * page table levels */
> + msk_clr = pmd_pgprot(*(pmd_t*)pte);
> + case PG_LEVEL_1G: {
> + struct cpa_data cpa;
> + int do_split;
> +
> + msk_clr = pud_pgprot(*(pud_t*)pte);
> +
> + memset(&cpa, 0, sizeof(cpa));
> + cpa.vaddr = kaddr;
> + cpa.pages = &page;
> + cpa.mask_set = prot;
> + cpa.mask_clr = msk_clr;
> + cpa.numpages = 1;
> + cpa.flags = 0;
> + cpa.curpage = 0;
> + cpa.force_split = 0;
> +
> +
> + do_split = try_preserve_large_page(pte, (unsigned long)kaddr, &cpa);
> + if (do_split) {
> + spin_lock(&cpa_lock);
> + BUG_ON(split_large_page(&cpa, pte, (unsigned long)kaddr));
> + spin_unlock(&cpa_lock);
> + }
This doesn't work in atomic contexts:
[ 28.263571] BUG: sleeping function called from invalid context at
mm/page_alloc.c:4048
[ 28.263575] in_atomic(): 1, irqs_disabled(): 1, pid: 2433, name:
gnome-terminal
[ 28.263576] INFO: lockdep is turned off.
[ 28.263578] irq event stamp: 0
[ 28.263580] hardirqs last enabled at (0): [< (null)>]
(null)
[ 28.263584] hardirqs last disabled at (0): [<ffffffff840af28a>]
copy_process.part.25+0x62a/0x1e90
[ 28.263587] softirqs last enabled at (0): [<ffffffff840af28a>]
copy_process.part.25+0x62a/0x1e90
[ 28.263588] softirqs last disabled at (0): [< (null)>]
(null)
[ 28.263591] CPU: 0 PID: 2433 Comm: gnome-terminal Tainted: G W
4.13.0-rc5-xpfo+ #86
[ 28.263592] Hardware name: LENOVO 20BTS1N700/20BTS1N700, BIOS
N14ET28W (1.06 ) 03/12/2015
[ 28.263593] Call Trace:
[ 28.263598] dump_stack+0x8e/0xd6
[ 28.263601] ___might_sleep+0x164/0x250
[ 28.263604] __might_sleep+0x4a/0x80
[ 28.263607] __alloc_pages_nodemask+0x2b3/0x3e0
[ 28.263611] alloc_pages_current+0x6a/0xe0
[ 28.263614] split_large_page+0x4e/0x360
[ 28.263618] set_kpte+0x12c/0x150
[ 28.263623] xpfo_kunmap+0x7e/0xa0
[ 28.263627] wp_page_copy+0x16e/0x800
[ 28.263631] do_wp_page+0x9a/0x580
[ 28.263633] __handle_mm_fault+0xb1c/0x1130
[ 28.263638] handle_mm_fault+0x178/0x350
[ 28.263641] __do_page_fault+0x26e/0x510
[ 28.263644] do_page_fault+0x30/0x80
[ 28.263647] page_fault+0x28/0x30
split_large_page calls alloc_page with GFP_KERNEL. switching to
use GFP_ATOMIC in this path works locally for me.
Thanks,
Laura
> +
> + break;
> + }
> + case PG_LEVEL_512G:
> + /* fallthrough, splitting infrastructure doesn't
> + * support 512G pages. */
> + default:
> + BUG();
> + }
> +
> +}
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