From: Steven Price <steven.price@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org
Cc: linux-mm@kvack.org, linux-arch@vger.kernel.org,
Will Deacon <will@kernel.org>,
Dave P Martin <Dave.Martin@arm.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Kevin Brodsky <kevin.brodsky@arm.com>,
Andrey Konovalov <andreyknvl@google.com>,
Peter Collingbourne <pcc@google.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v5 22/25] arm64: mte: Enable swap of tagged pages
Date: Thu, 25 Jun 2020 12:37:40 +0100 [thread overview]
Message-ID: <c9aa526c-b85f-4f73-828c-7fc0c4e7fbb2@arm.com> (raw)
In-Reply-To: <20200624175244.25837-23-catalin.marinas@arm.com>
On 24/06/2020 18:52, Catalin Marinas wrote:
> From: Steven Price <steven.price@arm.com>
>
> When swapping pages out to disk it is necessary to save any tags that
> have been set, and restore when swapping back in. Make use of the new
> page flag (PG_ARCH_2, locally named PG_mte_tagged) to identify pages
> with tags. When swapping out these pages the tags are stored in memory
> and later restored when the pages are brought back in. Because shmem can
> swap pages back in without restoring the userspace PTE it is also
> necessary to add a hook for shmem.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> [catalin.marinas@arm.com: move function prototypes to mte.h]
> [catalin.marinas@arm.com: drop '_tags' from arch_swap_restore_tags()]
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Will Deacon <will@kernel.org>
> ---
>
> Notes:
> New in v4.
>
[...]
> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
> index 3e08aea56e7a..1712c504df15 100644
> --- a/arch/arm64/kernel/mte.c
> +++ b/arch/arm64/kernel/mte.c
> @@ -10,6 +10,8 @@
> #include <linux/sched.h>
> #include <linux/sched/mm.h>
> #include <linux/string.h>
> +#include <linux/swap.h>
> +#include <linux/swapops.h>
> #include <linux/thread_info.h>
> #include <linux/uio.h>
>
> @@ -18,15 +20,30 @@
> #include <asm/ptrace.h>
> #include <asm/sysreg.h>
>
> +static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
> +{
> + pte_t old_pte = READ_ONCE(*ptep);
> +
> + if (check_swap && is_swap_pte(old_pte)) {
> + swp_entry_t entry = pte_to_swp_entry(old_pte);
> +
> + if (!non_swap_entry(entry) && mte_restore_tags(entry, page))
> + return;
> + }
> +
> + mte_clear_page_tags(page_address(page));
> +}
> +
> void mte_sync_tags(pte_t *ptep, pte_t pte)
> {
> struct page *page = pte_page(pte);
> long i, nr_pages = compound_nr(page);
> + bool check_swap = nr_pages == 0;
>
> /* if PG_mte_tagged is set, tags have already been initialised */
> for (i = 0; i < nr_pages; i++, page++) {
This is broken - for check_swap to be true, nr_pages==0, which means we
never enter the loop and nothing happens...
Except I don't believe compound_nr() will return 0 - it's defined as:
static inline unsigned long compound_nr(struct page *page)
{
return 1UL << compound_order(page);
}
Changing it to nr_pages==1 works for me.
Steve
next prev parent reply other threads:[~2020-06-25 11:37 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 17:52 [PATCH v5 00/25] arm64: Memory Tagging Extension user-space support Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 01/25] arm64: mte: system register definitions Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 02/25] arm64: mte: CPU feature detection and initial sysreg configuration Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 03/25] arm64: mte: Use Normal Tagged attributes for the linear map Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 04/25] arm64: mte: Add specific SIGSEGV codes Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 05/25] arm64: mte: Handle synchronous and asynchronous tag check faults Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 06/25] mm: Add PG_ARCH_2 page flag Catalin Marinas
2020-06-24 18:33 ` Andrew Morton
2020-06-24 18:36 ` Matthew Wilcox
2020-06-24 18:36 ` Matthew Wilcox
2020-06-25 17:10 ` Catalin Marinas
2020-07-01 17:30 ` Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 07/25] arm64: mte: Clear the tags when a page is mapped in user-space with PROT_MTE Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 08/25] arm64: mte: Tags-aware copy_{user_,}highpage() implementations Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 09/25] arm64: Avoid unnecessary clear_user_page() indirection Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 10/25] arm64: mte: Tags-aware aware memcmp_pages() implementation Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 11/25] mm: Introduce arch_calc_vm_flag_bits() Catalin Marinas
2020-06-24 18:36 ` Andrew Morton
2020-06-24 18:36 ` Andrew Morton
2020-06-25 17:34 ` Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 12/25] arm64: mte: Add PROT_MTE support to mmap() and mprotect() Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 13/25] mm: Introduce arch_validate_flags() Catalin Marinas
2020-06-24 18:37 ` Andrew Morton
2020-06-24 17:52 ` [PATCH v5 14/25] arm64: mte: Validate the PROT_MTE request via arch_validate_flags() Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 15/25] mm: Allow arm64 mmap(PROT_MTE) on RAM-based files Catalin Marinas
2020-06-24 18:42 ` Andrew Morton
2020-06-24 17:52 ` [PATCH v5 16/25] arm64: mte: Allow user control of the tag check mode via prctl() Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 17/25] arm64: mte: Allow user control of the generated random tags " Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 18/25] arm64: mte: Restore the GCR_EL1 register after a suspend Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 19/25] arm64: mte: Add PTRACE_{PEEK,POKE}MTETAGS support Catalin Marinas
2020-06-25 17:10 ` Luis Machado
2020-07-01 17:16 ` Catalin Marinas
2020-07-01 17:32 ` Luis Machado
2020-07-03 13:18 ` Catalin Marinas
2020-07-03 10:50 ` Catalin Marinas
2020-07-03 10:50 ` Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 20/25] fs: Handle intra-page faults in copy_mount_options() Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 21/25] mm: Add arch hooks for saving/restoring tags Catalin Marinas
2020-06-24 18:45 ` Andrew Morton
2020-06-25 9:04 ` Steven Price
2020-06-25 12:09 ` Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 22/25] arm64: mte: Enable swap of tagged pages Catalin Marinas
2020-06-25 11:37 ` Steven Price [this message]
2020-06-25 11:59 ` Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 23/25] arm64: mte: Save tags when hibernating Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 24/25] arm64: mte: Kconfig entry Catalin Marinas
2020-06-24 17:52 ` [PATCH v5 25/25] arm64: mte: Add Memory Tagging Extension documentation Catalin Marinas
2020-06-25 12:22 ` Szabolcs Nagy
2020-06-25 12:22 ` Szabolcs Nagy
2020-06-26 14:54 ` Catalin Marinas
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