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References: <20200821085011.28878-1-chris@chris-wilson.co.uk> <20200821100902.GG3354@suse.de>
Subject: Re: [PATCH] mm: Track page table modifications in __apply_to_page_range() construction
From:   Chris Wilson <chris@chris-wilson.co.uk>
Cc:     linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org,
        linux-mm@kvack.org, Pavel Machek <pavel@ucw.cz>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Dave Airlie <airlied@redhat.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        David Vrabel <david.vrabel@citrix.com>, stable@vger.kernel.org
To:     Joerg Roedel <jroedel@suse.de>
Date:   Fri, 21 Aug 2020 11:13:36 +0100
Message-ID: <159800481672.29194.17217138842959831589@build.alporthouse.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Quoting Joerg Roedel (2020-08-21 11:09:02)
> @@ -2333,6 +2339,7 @@ static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr,
>         pgd_t *pgd;
>         unsigned long next;
>         unsigned long end = addr + size;
> +       pgtbl_mod_mask mask = 0;
>         int err = 0;
>  
>         if (WARN_ON(addr >= end))
> @@ -2343,11 +2350,14 @@ static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr,
>                 next = pgd_addr_end(addr, end);
>                 if (!create && pgd_none_or_clear_bad(pgd))
>                         continue;
> -               err = apply_to_p4d_range(mm, pgd, addr, next, fn, data, create);
> +               err = apply_to_p4d_range(mm, pgd, addr, next, fn, data, create, &mask);
>                 if (err)
>                         break;
>         } while (pgd++, addr = next, addr != end);
>  
> +       if (mask & ARCH_PAGE_TABLE_SYNC_MASK)
> +               arch_sync_kernel_mappings(addr, addr + size);

We need to store the initial addr, as here addr == end [or earlier on
earlier], so range is (start, addr).
-Chris