From: Matthew Wilcox <willy@infradead.org>
To: Joao Martins <joao.m.martins@oracle.com>
Cc: linux-nvdimm@lists.01.org,
Dan Williams <dan.j.williams@intel.com>,
Vishal Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Ira Weiny <ira.weiny@intel.com>,
Alex Williamson <alex.williamson@redhat.com>,
Cornelia Huck <cohuck@redhat.com>,
kvm@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H . Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Liran Alon <liran.alon@oracle.com>,
Nikita Leshenko <nikita.leshchenko@oracle.com>,
Barret Rhoden <brho@google.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [PATCH RFC 01/10] mm: Add pmd support for _PAGE_SPECIAL
Date: Mon, 3 Feb 2020 13:34:42 -0800 [thread overview]
Message-ID: <20200203213442.GK8731@bombadil.infradead.org> (raw)
In-Reply-To: <20200110190313.17144-2-joao.m.martins@oracle.com>
On Fri, Jan 10, 2020 at 07:03:04PM +0000, Joao Martins wrote:
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -293,6 +293,15 @@ static inline int pgd_devmap(pgd_t pgd)
> {
> return 0;
> }
> +#endif
> +
> +#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
> +static inline int pmd_special(pmd_t pmd)
> +{
> + return !!(pmd_flags(pmd) & _PAGE_SPECIAL);
> +}
> +#endif
The ifdef/endif don't make much sense here; x86 does have PTE_SPECIAL,
and this is an x86 header file, so that can be assumed.
> +++ b/mm/gup.c
> @@ -2079,6 +2079,9 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
> return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr);
> }
>
> + if (pmd_special(orig))
> + return 0;
Here, you're calling it unconditionally. I think you need a pmd_special()
conditionally defined in include/asm-generic/pgtable.h
+#ifndef CONFIG_ARCH_HAS_PTE_SPECIAL
+static inline bool pmd_special(pmd_t pmd)
+{
+ return false;
+}
+#endif
(oh, and plese use bool instead of int; I know that's different from
pte_special(), but pte_special() predates bool and nobody's done the work
to convert it yet)
> +++ b/mm/huge_memory.c
> @@ -791,6 +791,8 @@ static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
> entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
> if (pfn_t_devmap(pfn))
> entry = pmd_mkdevmap(entry);
> + else if (pfn_t_special(pfn))
> + entry = pmd_mkspecial(entry);
Again, we'll need a generic one.
> @@ -823,8 +825,7 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write)
> * but we need to be consistent with PTEs and architectures that
> * can't support a 'special' bit.
> */
> - BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
> - !pfn_t_devmap(pfn));
> + BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
Should that rather be ...
+ BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
+ !pfn_t_devmap(pfn) && !pfn_t_special(pfn));
I also think this comment needs adjusting:
/*
* There is no pmd_special() but there may be special pmds, e.g.
* in a direct-access (dax) mapping, so let's just replicate the
* !CONFIG_ARCH_HAS_PTE_SPECIAL case from vm_normal_page() here.
*/
next prev parent reply other threads:[~2020-02-03 21:34 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 19:03 [PATCH RFC 00/10] device-dax: Support devices without PFN metadata Joao Martins
2020-01-10 19:03 ` [PATCH RFC 01/10] mm: Add pmd support for _PAGE_SPECIAL Joao Martins
2020-02-03 21:34 ` Matthew Wilcox [this message]
2020-02-04 16:14 ` Joao Martins
2020-01-10 19:03 ` [PATCH RFC 02/10] mm: Handle pmd entries in follow_pfn() Joao Martins
2020-02-03 21:37 ` Matthew Wilcox
2020-02-04 16:17 ` Joao Martins
2020-01-10 19:03 ` [PATCH RFC 03/10] mm: Add pud support for _PAGE_SPECIAL Joao Martins
2020-01-10 19:03 ` [PATCH RFC 04/10] mm: Handle pud entries in follow_pfn() Joao Martins
2020-01-10 19:03 ` [PATCH RFC 05/10] device-dax: Do not enforce MADV_DONTFORK on mmap() Joao Martins
2020-01-10 19:03 ` [PATCH RFC 06/10] device-dax: Introduce pfn_flags helper Joao Martins
2020-01-10 19:03 ` [PATCH RFC 07/10] device-dax: Add support for PFN_SPECIAL flags Joao Martins
2020-01-10 19:03 ` [PATCH RFC 08/10] dax/pmem: Add device-dax support for PFN_MODE_NONE Joao Martins
2020-01-10 19:03 ` [PATCH RFC 09/10] vfio/type1: Use follow_pfn for VM_FPNMAP VMAs Joao Martins
2020-02-07 21:08 ` Jason Gunthorpe
2020-02-11 16:23 ` Joao Martins
2020-02-11 16:50 ` Jason Gunthorpe
2020-01-10 19:03 ` [PATCH RFC 10/10] nvdimm/e820: add multiple namespaces support Joao Martins
2020-02-04 15:28 ` Barret Rhoden
2020-02-04 16:44 ` Dan Williams
2020-02-04 18:20 ` Barret Rhoden
2020-02-04 19:24 ` Joao Martins
2020-02-04 21:43 ` Dan Williams
2020-02-04 21:57 ` Barret Rhoden
2020-02-04 1:24 ` [PATCH RFC 00/10] device-dax: Support devices without PFN metadata Dan Williams
2020-02-04 19:07 ` Joao Martins
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