linux-kernel - Re: [PATCH] mm: Track page table modifications in __apply_to_page

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Message-ID: <159800988352.29194.8498025838223804532@build.alporthouse.com>
Date:   Fri, 21 Aug 2020 12:38:03 +0100
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        linux-mm@...ck.org, Pavel Machek <pavel@....cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Dave Airlie <airlied@...hat.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Vrabel <david.vrabel@...rix.com>, stable@...r.kernel.org
Subject: Re: [PATCH] mm: Track page table modifications in __apply_to_page_range() construction

Quoting Chris Wilson (2020-08-21 11:39:19)
> Quoting Joerg Roedel (2020-08-21 11:23:43)
> > On Fri, Aug 21, 2020 at 11:13:36AM +0100, Chris Wilson wrote:
> > > We need to store the initial addr, as here addr == end [or earlier on
> > > earlier], so range is (start, addr).
> > 
> > Right, I missed that, thanks for pointing it out.
> 
> And with that (start, addr)
> 
> Tested-by: Chris Wilson <chris@...is-wilson.co.uk> #x86-32

In the version I tested, I also had

@@ -2216,7 +2216,7 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,

        if (create) {
                pte = (mm == &init_mm) ?
-                       pte_alloc_kernel(pmd, addr) :
+                       pte_alloc_kernel_track(pmd, addr, mask) :
                        pte_alloc_map_lock(mm, pmd, addr, &ptl);
                if (!pte)
                        return -ENOMEM;

And that PGTBL_PMD_MODIFIED makes a difference.
-Chris