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Date:   Wed, 20 Apr 2022 19:14:15 +0200
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Subject: Re: [PATCH v2 2/8] mm/debug_vm_pgtable: add tests for
 __HAVE_ARCH_PTE_SWP_EXCLUSIVE
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To:     David Hildenbrand <david@redhat.com>, linux-kernel@vger.kernel.org
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        David Rientjes <rientjes@google.com>,
        Shakeel Butt <shakeelb@google.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Yang Shi <shy828301@gmail.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Matthew Wilcox <willy@infradead.org>,
        Jann Horn <jannh@google.com>, Michal Hocko <mhocko@kernel.org>,
        Nadav Amit <namit@vmware.com>, Rik van Riel <riel@surriel.com>,
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        Donald Dutile <ddutile@redhat.com>,
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        Oleg Nesterov <oleg@redhat.com>, Jan Kara <jack@suse.cz>,
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        Pedro Gomes <pedrodemargomes@gmail.com>,
        Oded Gabbay <oded.gabbay@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
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        Alexander Gordeev <agordeev@linux.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
        linux-mm@kvack.org, x86@kernel.org,
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References: <20220329164329.208407-1-david@redhat.com>
 <20220329164329.208407-3-david@redhat.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20220329164329.208407-3-david@redhat.com>
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On 3/29/22 18:43, David Hildenbrand wrote:
> Let's test that __HAVE_ARCH_PTE_SWP_EXCLUSIVE works as expected.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/debug_vm_pgtable.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index db2abd9e415b..55f1a8dc716f 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -837,6 +837,19 @@ static void __init pmd_soft_dirty_tests(struct pgtable_debug_args *args) { }
>  static void __init pmd_swap_soft_dirty_tests(struct pgtable_debug_args *args) { }
>  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  
> +static void __init pte_swap_exclusive_tests(struct pgtable_debug_args *args)
> +{
> +#ifdef __HAVE_ARCH_PTE_SWP_EXCLUSIVE
> +	pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot);
> +
> +	pr_debug("Validating PTE swap exclusive\n");
> +	pte = pte_swp_mkexclusive(pte);
> +	WARN_ON(!pte_swp_exclusive(pte));

I guess only this WARN_ON must be guarded by the #ifdef, but doesn't matter
that much - won't gain significantly more test coverage.

> +	pte = pte_swp_clear_exclusive(pte);
> +	WARN_ON(pte_swp_exclusive(pte));
> +#endif /* __HAVE_ARCH_PTE_SWP_EXCLUSIVE */
> +}
> +
>  static void __init pte_swap_tests(struct pgtable_debug_args *args)
>  {
>  	swp_entry_t swp;
> @@ -1288,6 +1301,8 @@ static int __init debug_vm_pgtable(void)
>  	pte_swap_soft_dirty_tests(&args);
>  	pmd_swap_soft_dirty_tests(&args);
>  
> +	pte_swap_exclusive_tests(&args);
> +
>  	pte_swap_tests(&args);
>  	pmd_swap_tests(&args);
>