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From: Matthew Wilcox <willy@infradead.org>
To: Alexander Potapenko <glider@google.com>
Cc: Michal Hocko <mhocko@kernel.org>,
	Vegard Nossum <vegard.nossum@oracle.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dmitry Vyukov <dvyukov@google.com>,
	Marco Elver <elver@google.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Linux Memory Management List <linux-mm@kvack.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Andy Lutomirski <luto@kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Christoph Hellwig <hch@infradead.org>,
	Christoph Hellwig <hch@lst.de>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	David Miller <davem@davemloft.net>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
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	Harry Wentland <harry.wentland@amd.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Ilya Leoshkevich <iii@linux.ibm.com>, Ingo Molnar <mingo@elte.hu>,
	Jason Wang <jasowang@redhat.com>, Jens Axboe <axboe@kernel.dk>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Mark Rutland <mark.rutland@arm.com>,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Michal Simek <monstr@monstr.eu>, Petr Mladek <pmladek@suse.com>,
	Qian Cai <cai@lca.pw>, Randy Dunlap <rdunlap@infradead.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
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	Takashi Iwai <tiwai@suse.com>, Theodore Ts'o <tytso@mit.edu>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Wolfram Sang <wsa@the-dreams.de>
Subject: Re: [PATCH v5 03/38] kmsan: gfp: introduce __GFP_NO_KMSAN_SHADOW
Date: Wed, 25 Mar 2020 11:09:41 -0700	[thread overview]
Message-ID: <20200325180941.GD22483@bombadil.infradead.org> (raw)
In-Reply-To: <CAG_fn=Xq5shgLmF6H9T1NWPhAaQ4prXezkbLB3P2etER2ODd6g@mail.gmail.com>

On Wed, Mar 25, 2020 at 07:03:32PM +0100, Alexander Potapenko wrote:
> > I would suggest using bits in the section labelled:
> >
> >         /* Unserialized, strictly 'current' */
> 
> The main problem is that |current| is unavailable in the interrupt
> context, so we'll also need to:
>  - disable interrupts when preparing for a KMSAN internal memory
> allocation - sounds costly, huh?
>  - store the context flag in a per-cpu variable in the case |current|
> is unavailable.

It's not /unavailable/ ... it's whatever task happens to be running at
the time the interrupt is triggered.  You can borrow its task_struct.
You'll have to save off the current value of the flag before setting it,
just like memalloc_nofs_save() does.

But this does rather call into question whether Michal's advice to use
task_struct is good advice to begin with.  For memalloc_nofs/noio,
it works well this way because allocations in interrupt context are
inherently at a more restrictive context than task level.  It's not clear
to me what this kmsan GFP flag is being used for, and whether allocations
that happen in interrupt context should inherit the kmsan setting.
I will have to read these patches more carefully to determine that;
I was really just responding to the "where can I find some free bits"
part of the question.


  reply	other threads:[~2020-03-25 18:09 UTC|newest]

Thread overview: 94+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-25 16:12 [PATCH v5 00/38] Add KernelMemorySanitizer infrastructure glider
2020-03-25 16:12 ` [PATCH v5 01/38] stackdepot: reserve 5 extra bits in depot_stack_handle_t glider
2020-03-30 13:36   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 02/38] kmsan: add ReST documentation glider
2020-03-30 14:32   ` Andrey Konovalov
2020-04-13 14:45     ` Alexander Potapenko
2020-03-25 16:12 ` [PATCH v5 03/38] kmsan: gfp: introduce __GFP_NO_KMSAN_SHADOW glider
2020-03-25 16:19   ` Michal Hocko
2020-03-25 17:26     ` Alexander Potapenko
2020-03-25 17:40       ` Alexander Potapenko
2020-03-25 17:49         ` Matthew Wilcox
2020-03-25 18:03           ` Alexander Potapenko
2020-03-25 18:09             ` Matthew Wilcox [this message]
2020-03-25 18:30               ` Alexander Potapenko
2020-03-25 18:43                 ` Michal Hocko
2020-03-25 18:40           ` Michal Hocko
2020-03-25 18:38         ` Michal Hocko
2020-03-27 12:20           ` Alexander Potapenko
2020-04-25  9:45             ` Alexander Potapenko
2020-03-25 17:43       ` Michal Hocko
2020-03-25 16:12 ` [PATCH v5 04/38] kmsan: introduce __no_sanitize_memory and __SANITIZE_MEMORY__ glider
2020-03-30 13:37   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 05/38] kmsan: reduce vmalloc space glider
2020-03-30 13:48   ` Andrey Konovalov
2020-04-14 14:21     ` Alexander Potapenko
2020-04-23 19:14       ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 06/38] kmsan: add KMSAN runtime core glider
2020-03-25 16:12 ` [PATCH v5 07/38] kmsan: KMSAN compiler API implementation glider
2020-03-25 16:12 ` [PATCH v5 08/38] kmsan: add KMSAN hooks for kernel subsystems glider
2020-03-25 16:12 ` [PATCH v5 09/38] kmsan: stackdepot: don't allocate KMSAN metadata for stackdepot glider
2020-04-23 19:22   ` Andrey Konovalov
2020-04-25  9:46     ` Alexander Potapenko
2020-03-25 16:12 ` [PATCH v5 10/38] kmsan: define READ_ONCE_NOCHECK() glider
2020-04-23 19:20   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 11/38] kmsan: make READ_ONCE_TASK_STACK() return initialized values glider
2020-04-23 19:15   ` Andrey Konovalov
2020-04-23 19:18     ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 12/38] kmsan: x86: sync metadata pages on page fault glider
2020-04-23 19:15   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 13/38] kmsan: add tests for KMSAN glider
2020-04-23 19:02   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 14/38] crypto: kmsan: disable accelerated configs under KMSAN glider
2020-04-23 18:50   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 15/38] kmsan: x86: disable UNWINDER_ORC " glider
2020-04-14 17:52   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 16/38] kmsan: x86/asm: softirq: add KMSAN IRQ entry hooks glider
2020-04-14 17:54   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 17/38] kmsan: disable KMSAN instrumentation for certain kernel parts glider
2020-04-14 17:56   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 18/38] kmsan: mm: call KMSAN hooks from SLUB code glider
2020-03-25 16:12 ` [PATCH v5 19/38] kmsan: mm: maintain KMSAN metadata for page operations glider
2020-03-25 16:12 ` [PATCH v5 20/38] kmsan: handle memory sent to/from USB glider
2020-04-14 14:46   ` Andrey Konovalov
2020-04-14 15:50     ` Alan Stern
2020-04-14 17:48       ` Andrey Konovalov
2020-04-14 20:45         ` Alan Stern
2020-04-27 13:59           ` Alexander Potapenko
2020-03-25 16:12 ` [PATCH v5 21/38] kmsan: handle task creation and exiting glider
2020-03-25 16:12 ` [PATCH v5 22/38] kmsan: net: check the value of skb before sending it to the network glider
2020-04-27 14:02   ` Alexander Potapenko
2020-03-25 16:12 ` [PATCH v5 23/38] kmsan: printk: treat the result of vscnprintf() as initialized glider
2020-04-14 14:37   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 24/38] kmsan: disable instrumentation of certain functions glider
2020-04-14 15:04   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 25/38] kmsan: unpoison |tlb| in arch_tlb_gather_mmu() glider
2020-04-08 16:07   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 26/38] kmsan: use __msan_ string functions where possible glider
2020-03-25 16:12 ` [PATCH v5 27/38] kmsan: hooks for copy_to_user() and friends glider
2020-03-25 16:12 ` [PATCH v5 28/38] kmsan: init: call KMSAN initialization routines glider
2020-04-08 16:04   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 29/38] kmsan: enable KMSAN builds glider
2020-04-14 14:56   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 30/38] kmsan: handle /dev/[u]random glider
2020-04-08 16:03   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 31/38] kmsan: virtio: check/unpoison scatterlist in vring_map_one_sg() glider
2020-03-25 16:12 ` [PATCH v5 32/38] kmsan: disable strscpy() optimization under KMSAN glider
2020-04-08 16:00   ` Andrey Konovalov
2020-04-13 14:19     ` Alexander Potapenko
2020-04-13 15:32       ` Steven Rostedt
2020-04-13 16:16         ` Alexander Potapenko
2020-03-25 16:12 ` [PATCH v5 33/38] kmsan: add iomap support glider
2020-04-08 15:57   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 34/38] kmsan: dma: unpoison memory mapped by dma_direct_map_page() glider
2020-03-25 16:19   ` Christoph Hellwig
2020-03-27 17:03     ` Alexander Potapenko
2020-03-27 17:06       ` Christoph Hellwig
2020-03-27 18:46         ` Alexander Potapenko
2020-03-28  8:52           ` Christoph Hellwig
2020-04-14 15:26             ` Alexander Potapenko
2020-03-25 16:12 ` [PATCH v5 35/38] kmsan: disable physical page merging in biovec glider
2020-03-25 16:12 ` [PATCH v5 36/38] x86: kasan: kmsan: support CONFIG_GENERIC_CSUM on x86, enable it for KASAN/KMSAN glider
2020-04-08 15:53   ` Andrey Konovalov
2020-03-25 16:12 ` [PATCH v5 37/38] kmsan: x86/uprobes: unpoison regs in arch_uprobe_exception_notify() glider
2020-03-25 16:12 ` [PATCH v5 38/38] kmsan: block: skip bio block merging logic for KMSAN glider

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