From: James Morse <james.morse@arm.com>
To: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: sashal@kernel.org, mark.rutland@arm.com, vladimir.murzin@arm.com,
corbet@lwn.net, marc.zyngier@arm.com, catalin.marinas@arm.com,
bhsharma@redhat.com, kexec@lists.infradead.org,
linux-kernel@vger.kernel.org, jmorris@namei.org,
linux-mm@kvack.org, ebiederm@xmission.com,
matthias.bgg@gmail.com, will@kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 10/17] arm64, trans_pgd: adjust trans_pgd_create_copy interface
Date: Fri, 6 Sep 2019 16:20:55 +0100 [thread overview]
Message-ID: <21f6eb6f-be3a-a715-a37c-2f59183ed183@arm.com> (raw)
In-Reply-To: <20190821183204.23576-11-pasha.tatashin@soleen.com>
Hi Pavel,
On 21/08/2019 19:31, Pavel Tatashin wrote:
> Make trans_pgd_create_copy inline with the other functions in
> trans_pgd: use the trans_pgd_info argument, and also use the
> trans_pgd_create_empty.
>
> Note, that the functions that are called by trans_pgd_create_copy are
> not yet adjusted to be compliant with trans_pgd: they do not yet use
> the provided allocator, do not check for generic errors, and do not yet
> use the flags in info argument.
> diff --git a/arch/arm64/include/asm/trans_pgd.h b/arch/arm64/include/asm/trans_pgd.h
> index 26e5a63676b5..f4a5f255d4a7 100644
> --- a/arch/arm64/include/asm/trans_pgd.h
> +++ b/arch/arm64/include/asm/trans_pgd.h
> @@ -43,7 +43,12 @@ struct trans_pgd_info {
> /* Create and empty trans_pgd page table */
> int trans_pgd_create_empty(struct trans_pgd_info *info, pgd_t **trans_pgd);
>
> -int trans_pgd_create_copy(pgd_t **dst_pgdp, unsigned long start,
> +/*
> + * Create trans_pgd and copy entries from from_table to trans_pgd in range
> + * [start, end)
> + */
> +int trans_pgd_create_copy(struct trans_pgd_info *info, pgd_t **trans_pgd,
> + pgd_t *from_table, unsigned long start,
> unsigned long end);
This creates a copy of the linear-map. Why does it need to be told from_table?
> diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
> index 8c2641a9bb09..8bb602e91065 100644
> --- a/arch/arm64/kernel/hibernate.c
> +++ b/arch/arm64/kernel/hibernate.c
> @@ -323,15 +323,42 @@ int swsusp_arch_resume(void)
> phys_addr_t phys_hibernate_exit;
> void __noreturn (*hibernate_exit)(phys_addr_t, phys_addr_t, void *,
> void *, phys_addr_t, phys_addr_t);
> + struct trans_pgd_info trans_info = {
> + .trans_alloc_page = hibernate_page_alloc,
> + .trans_alloc_arg = (void *)GFP_ATOMIC,
> + /*
> + * Resume will overwrite areas that may be marked read only
> + * (code, rodata). Clear the RDONLY bit from the temporary
> + * mappings we use during restore.
> + */
> + .trans_flags = TRANS_MKWRITE,
> + };
> + /*
> + * debug_pagealloc will removed the PTE_VALID bit if the page isn't in
> + * use by the resume kernel. It may have been in use by the original
> + * kernel, in which case we need to put it back in our copy to do the
> + * restore.
> + *
> + * Before marking this entry valid, check the pfn should be mapped.
> + */
> + if (debug_pagealloc_enabled())
> + trans_info.trans_flags |= (TRANS_MKVALID | TRANS_CHECKPFN);
The debug_pagealloc_enabled() check should be with the code that generates a different
entry. Whether the different entry is correct needs to be considered with
debug_pagealloc_enabled() in mind. You are making this tricky logic less clear.
There is no way the existing code invents an entry for a !pfn_valid() page. With your
'checkpfn' flag, this thing can. You don't need to generalise this for hypothetical users.
If kexec needs to create mappings for bogus pages, I'd like to know why.
> /*
> * Restoring the memory image will overwrite the ttbr1 page tables.
> * Create a second copy of just the linear map, and use this when
> * restoring.
> */
> - rc = trans_pgd_create_copy(&tmp_pg_dir, PAGE_OFFSET, 0);
> - if (rc)
> + rc = trans_pgd_create_copy(&trans_info, &tmp_pg_dir, init_mm.pgd,
> + PAGE_OFFSET, 0);
> + if (rc) {
> + if (rc == -ENOMEM)
> + pr_err("Failed to allocate memory for temporary page tables.\n");
> + else if (rc == -ENXIO)
> + pr_err("Tried to set PTE for PFN that does not exist\n");
> goto out;
> + }
If you think the distinction for this error message is useful, it would be clearer to
change it in the current hibernate code before you move it. (_copy_pte() to return an
error, instead of silently failing). Done here, this is unrelated noise.
I doubt this is specific to kexec.
Thanks,
James
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next prev parent reply other threads:[~2019-09-06 15:21 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-21 18:31 [PATCH v3 00/17] arm64: MMU enabled kexec relocation Pavel Tatashin
2019-08-21 18:31 ` [PATCH v3 01/17] kexec: quiet down kexec reboot Pavel Tatashin
2019-09-06 15:17 ` James Morse
2019-09-06 15:35 ` Pavel Tatashin
2019-08-21 18:31 ` [PATCH v3 02/17] arm64, hibernate: use get_safe_page directly Pavel Tatashin
2019-09-06 15:17 ` James Morse
2019-09-06 15:39 ` Pavel Tatashin
2019-08-21 18:31 ` [PATCH v3 03/17] arm64, hibernate: remove gotos in create_safe_exec_page Pavel Tatashin
2019-09-06 15:17 ` James Morse
2019-09-06 15:41 ` Pavel Tatashin
2019-08-21 18:31 ` [PATCH v3 04/17] arm64, hibernate: rename dst to page " Pavel Tatashin
2019-09-06 15:17 ` James Morse
2019-09-06 15:41 ` Pavel Tatashin
2019-08-21 18:31 ` [PATCH v3 05/17] arm64, hibernate: check pgd table allocation Pavel Tatashin
2019-09-06 15:17 ` James Morse
2019-09-06 15:44 ` Pavel Tatashin
2019-08-21 18:31 ` [PATCH v3 06/17] arm64, hibernate: add trans_pgd public functions Pavel Tatashin
2019-09-06 15:18 ` James Morse
2019-09-06 16:00 ` Pavel Tatashin
2019-10-11 18:16 ` James Morse
2019-08-21 18:31 ` [PATCH v3 07/17] arm64, hibernate: move page handling function to new trans_pgd.c Pavel Tatashin
2019-09-06 15:18 ` James Morse
2019-09-06 17:41 ` Pavel Tatashin
2019-08-21 18:31 ` [PATCH v3 08/17] arm64, trans_pgd: make trans_pgd_map_page generic Pavel Tatashin
2019-09-06 15:20 ` James Morse
2019-09-06 18:58 ` Pavel Tatashin
2019-10-11 18:15 ` James Morse
2019-08-21 18:31 ` [PATCH v3 09/17] arm64, trans_pgd: add trans_pgd_create_empty Pavel Tatashin
2019-09-06 15:20 ` James Morse
2019-09-06 19:00 ` Pavel Tatashin
2019-08-21 18:31 ` [PATCH v3 10/17] arm64, trans_pgd: adjust trans_pgd_create_copy interface Pavel Tatashin
2019-09-06 15:20 ` James Morse [this message]
2019-09-06 19:03 ` Pavel Tatashin
2019-08-21 18:31 ` [PATCH v3 11/17] arm64, trans_pgd: add PUD_SECT_RDONLY Pavel Tatashin
2019-09-06 15:21 ` James Morse
2019-09-06 19:04 ` Pavel Tatashin
2019-08-21 18:31 ` [PATCH v3 12/17] arm64, trans_pgd: complete generalization of trans_pgds Pavel Tatashin
2019-09-06 15:23 ` James Morse
2019-09-06 19:06 ` Pavel Tatashin
2019-08-21 18:32 ` [PATCH v3 13/17] kexec: add machine_kexec_post_load() Pavel Tatashin
2019-08-21 18:32 ` [PATCH v3 14/17] arm64, kexec: move relocation function setup and clean up Pavel Tatashin
2019-08-21 18:32 ` [PATCH v3 15/17] arm64, kexec: add expandable argument to relocation function Pavel Tatashin
2019-08-21 18:32 ` [PATCH v3 16/17] arm64, kexec: configure trans_pgd page table for kexec Pavel Tatashin
2019-08-21 18:32 ` [PATCH v3 17/17] arm64, kexec: enable MMU during kexec relocation Pavel Tatashin
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