From: Barret Rhoden <brho@google.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
David Hildenbrand <david@redhat.com>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
linux-nvdimm@lists.01.org, x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, jason.zeng@intel.com
Subject: Re: [PATCH v5 1/2] mm: make dev_pagemap_mapping_shift() externally visible
Date: Mon, 16 Dec 2019 12:59:53 -0500 [thread overview]
Message-ID: <e004e742-f755-c22c-57bb-acfe30971c7d@google.com> (raw)
In-Reply-To: <20191213174702.GB31552@linux.intel.com>
On 12/13/19 12:47 PM, Sean Christopherson wrote:
>> +unsigned long dev_pagemap_mapping_shift(unsigned long address,
>> + struct mm_struct *mm)
>> +{
>> + pgd_t *pgd;
>> + p4d_t *p4d;
>> + pud_t *pud;
>> + pmd_t *pmd;
>> + pte_t *pte;
>> +
>> + pgd = pgd_offset(mm, address);
>> + if (!pgd_present(*pgd))
>> + return 0;
>> + p4d = p4d_offset(pgd, address);
>> + if (!p4d_present(*p4d))
>> + return 0;
>> + pud = pud_offset(p4d, address);
>> + if (!pud_present(*pud))
>> + return 0;
>> + if (pud_devmap(*pud))
>> + return PUD_SHIFT;
>> + pmd = pmd_offset(pud, address);
>> + if (!pmd_present(*pmd))
>> + return 0;
>> + if (pmd_devmap(*pmd))
>> + return PMD_SHIFT;
>> + pte = pte_offset_map(pmd, address);
>> + if (!pte_present(*pte))
>> + return 0;
>> + if (pte_devmap(*pte))
>> + return PAGE_SHIFT;
>> + return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(dev_pagemap_mapping_shift);
>
> This is basically a rehash of lookup_address_in_pgd(), and doesn't provide
> exactly what KVM needs. E.g. KVM works with levels instead of shifts, and
> it would be nice to provide the pte so that KVM can sanity check that the
> pfn from this walk matches the pfn it plans on mapping.
One minor issue is that the levels for lookup_address_in_pgd() and for
KVM differ in name, although not in value. lookup uses PG_LEVEL_4K = 1.
KVM uses PT_PAGE_TABLE_LEVEL = 1. The enums differ a little too: x86
has a name for a 512G page, etc. It's all in arch/x86.
Does KVM-x86 need its own names for the levels? If not, I could convert
the PT_PAGE_TABLE_* stuff to PG_LEVEL_* stuff.
>
> Instead of exporting dev_pagemap_mapping_shift(), what about replacing it
> with a patch to introduce lookup_address_mm() and export that?
>
> dev_pagemap_mapping_shift() could then wrap the new helper (if you want),
I might hold off on that for now, since that helper is used outside of
x86, and I don't know if 'level' makes sense outside of x86.
Thanks,
Barret
_______________________________________________
Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org
To unsubscribe send an email to linux-nvdimm-leave@lists.01.org
next prev parent reply other threads:[~2019-12-16 17:59 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-12 18:22 [PATCH v5 0/2] kvm: Use huge pages for DAX-backed files Barret Rhoden
2019-12-12 18:22 ` [PATCH v5 1/2] mm: make dev_pagemap_mapping_shift() externally visible Barret Rhoden
2019-12-13 17:47 ` Sean Christopherson
2019-12-13 18:13 ` Dan Williams
2019-12-16 17:59 ` Barret Rhoden [this message]
2019-12-18 0:18 ` Sean Christopherson
2020-01-15 18:33 ` Paolo Bonzini
2019-12-12 18:22 ` [PATCH v5 2/2] kvm: Use huge pages for DAX-backed files Barret Rhoden
2019-12-12 18:47 ` Liran Alon
2019-12-12 18:49 ` Liran Alon
2019-12-12 19:55 ` Barret Rhoden
2019-12-13 1:07 ` Liran Alon
2019-12-13 14:13 ` Barret Rhoden
2019-12-13 17:19 ` Sean Christopherson
2019-12-13 17:31 ` Liran Alon
2019-12-13 17:50 ` Sean Christopherson
2019-12-13 18:08 ` Liran Alon
2019-12-16 16:05 ` Barret Rhoden
2020-01-07 19:05 ` Sean Christopherson
2020-01-07 19:19 ` Barret Rhoden
2020-01-08 1:20 ` Sean Christopherson
2020-01-08 1:39 ` Dan Williams
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=e004e742-f755-c22c-57bb-acfe30971c7d@google.com \
--to=brho@google.com \
--cc=alexander.h.duyck@linux.intel.com \
--cc=david@redhat.com \
--cc=jason.zeng@intel.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nvdimm@lists.01.org \
--cc=pbonzini@redhat.com \
--cc=sean.j.christopherson@intel.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).