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From: "joro@8bytes.org" <joro@8bytes.org>
To: Chintan Pandya <cpandya@codeaurora.org>
Cc: "Kani, Toshi" <toshi.kani@hpe.com>,
	"Hocko, Michal" <MHocko@suse.com>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"wxf.wang@hisilicon.com" <wxf.wang@hisilicon.com>,
	"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"will.deacon@arm.com" <will.deacon@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"willy@infradead.org" <willy@infradead.org>,
	"guohanjun@huawei.com" <guohanjun@huawei.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"bp@suse.de" <bp@suse.de>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 2/2] x86/mm: implement free pmd/pte page interfaces
Date: Fri, 27 Apr 2018 14:48:29 +0200	[thread overview]
Message-ID: <20180427124828.GW15462@8bytes.org> (raw)
In-Reply-To: <5b237058-6617-6af3-8499-8836d95f538d@codeaurora.org>

On Fri, Apr 27, 2018 at 05:22:28PM +0530, Chintan Pandya wrote:
> I'm bit confused here. Are you pointing to race within ioremap/vmalloc
> framework while updating the page table or race during tlb ops. Since
> later is arch dependent, I would not comment. But if the race being
> discussed here while altering page tables, I'm not on the same page.

The race condition is between hardware and software. It is not
sufficient to just remove the software references to the page that is
about to be freed (by clearing the PMD/PUD), also the hardware
references in the page-walk cache need to be removed with a TLB flush.
Otherwise the hardware can use the freed (and possibly reused) page to
establish new TLB entries.



	Joerg

  reply	other threads:[~2018-04-27 12:48 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-14 18:01 [PATCH v2 0/2] fix memory leak / panic in ioremap huge pages Toshi Kani
2018-03-14 18:01 ` [PATCH v2 1/2] mm/vmalloc: Add interfaces to free unmapped page table Toshi Kani
2018-03-14 22:38   ` Andrew Morton
2018-03-15 14:27     ` Kani, Toshi
2018-03-14 18:01 ` [PATCH v2 2/2] x86/mm: implement free pmd/pte page interfaces Toshi Kani
2018-03-15  7:39   ` Chintan Pandya
2018-03-15 14:51     ` Kani, Toshi
2018-04-26 14:19   ` Joerg Roedel
2018-04-26 16:21     ` Kani, Toshi
2018-04-26 17:23       ` joro
2018-04-26 17:49         ` Kani, Toshi
2018-04-26 20:07           ` joro
2018-04-26 22:30             ` Kani, Toshi
2018-04-27  7:37               ` joro
2018-04-27 11:39                 ` Michal Hocko
2018-04-27 11:46                   ` joro
2018-04-27 11:52                 ` Chintan Pandya
2018-04-27 12:48                   ` joro [this message]
2018-04-27 13:42                     ` Chintan Pandya
2018-04-27 14:31                 ` Kani, Toshi
2018-04-28  9:02                   ` joro
2018-04-28 20:54                     ` Kani, Toshi
2018-04-30  7:30                       ` Chintan Pandya
2018-04-30 13:43                         ` Kani, Toshi

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