From: Lorenzo Stoakes <lstoakes@gmail.com>
To: Ryan Roberts <ryan.roberts@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
SeongJae Park <sj@kernel.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
damon@lists.linux.dev, Christoph Hellwig <hch@infradead.org>,
Uladzislau Rezki <urezki@gmail.com>
Subject: Re: [RESEND PATCH v1 1/5] mm: vmalloc must set pte via arch code
Date: Sat, 13 May 2023 14:14:18 +0100 [thread overview]
Message-ID: <db1b8b8f-c3ac-4dbb-8b15-125c0929856a@lucifer.local> (raw)
In-Reply-To: <20230511132113.80196-2-ryan.roberts@arm.com>
You've not cc'd the vmalloc reviewers, including the author of 3e9a9e256b1e
whose patch you purport to fix. Please remember to run get_maintainers.pl
on all files you patch and cc them at least on relevant patches.
Have added Christoph + Uladzislau as cc.
You'll definitely want an ack from Christoph on this!
On Thu, May 11, 2023 at 02:21:09PM +0100, Ryan Roberts wrote:
> It is bad practice to directly set pte entries within a pte table.
> Instead all modifications must go through arch-provided helpers such as
> set_pte_at() to give the arch code visibility and allow it to validate
> (and potentially modify) the operation.
This does make sense, and I see for example in xtensa that an arch-specific
instruction is issued under certain circumstances so I do suspect we should
do this.
As for validation, the function never indicates an error, so only in the
sense that a WARN_ON() could _in theory_ trigger is it being
validated. This might be quite a nitty point :) as set_pte_at() has no
means of indicating an error. But maybe to be pedantic 'check' rather than
'validate'?
>
> Fixes: 3e9a9e256b1e ("mm: add a vmap_pfn function")
Not sure if this is really 'fixing' anything, I mean ostensibly, but not
sure if the tag is relevant here, that is more so for a bug being
introduced, and unless an issue has arisen not sure if it's
appropriate. But this might be a nit, again!
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> ---
> mm/vmalloc.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 9683573f1225..d8d2fe797c55 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2899,10 +2899,13 @@ struct vmap_pfn_data {
> static int vmap_pfn_apply(pte_t *pte, unsigned long addr, void *private)
> {
> struct vmap_pfn_data *data = private;
> + pte_t ptent;
>
> if (WARN_ON_ONCE(pfn_valid(data->pfns[data->idx])))
> return -EINVAL;
> - *pte = pte_mkspecial(pfn_pte(data->pfns[data->idx++], data->prot));
> +
> + ptent = pte_mkspecial(pfn_pte(data->pfns[data->idx++], data->prot));
> + set_pte_at(&init_mm, addr, pte, ptent);
While we're refactoring, it'd be nice to stash data->pfns[data->idx] into a
local pfn variable.
> return 0;
> }
>
> --
> 2.25.1
>
next prev parent reply other threads:[~2023-05-13 13:14 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-11 13:21 [RESEND PATCH v1 0/5] Encapsulate PTE contents from non-arch code Ryan Roberts
2023-05-11 13:21 ` [RESEND PATCH v1 1/5] mm: vmalloc must set pte via arch code Ryan Roberts
2023-05-11 15:00 ` Zi Yan
2023-05-12 11:01 ` Ryan Roberts
2023-05-13 13:14 ` Lorenzo Stoakes [this message]
2023-05-15 8:29 ` Ryan Roberts
2023-05-15 11:25 ` Lorenzo Stoakes
2023-05-15 12:14 ` Ryan Roberts
2023-05-17 6:20 ` Christoph Hellwig
2023-05-17 6:23 ` Lorenzo Stoakes
2023-05-17 6:18 ` Christoph Hellwig
2023-05-11 13:21 ` [RESEND PATCH v1 2/5] mm: damon must atomically clear young on ptes and pmds Ryan Roberts
2023-05-11 15:01 ` Zi Yan
2023-05-11 13:21 ` [RESEND PATCH v1 3/5] mm: Fix failure to unmap pte on highmem systems Ryan Roberts
2023-05-11 15:01 ` Zi Yan
2023-05-11 13:21 ` [RESEND PATCH v1 4/5] mm: Add new ptep_deref() helper to fully encapsulate pte_t Ryan Roberts
2023-05-11 13:21 ` [RESEND PATCH v1 5/5] mm: ptep_deref() conversion Ryan Roberts
2023-05-11 17:37 ` kernel test robot
2023-05-12 10:50 ` Ryan Roberts
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