From: Juergen Gross <jgross@suse.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: George Dunlap <george.dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Tim Deegan <tim@xen.org>, Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH v2 5/9] x86/pagewalk: Helpers for reserved bit handling
Date: Fri, 24 Mar 2017 08:58:28 +0100 [thread overview]
Message-ID: <eda54533-b47a-b570-c543-b64d84f4bcf0@suse.com> (raw)
In-Reply-To: <58D4DDFF0200007800147138@suse.com>
On 24/03/17 08:51, Jan Beulich wrote:
>>>> On 24.03.17 at 06:45, <jgross@suse.com> wrote:
>> On 23/03/17 18:35, Andrew Cooper wrote:
>>> Would you prefer ~((uint64_t)_PAGE_PSE_PAT | (_PAGE_PSE_PAT - 1)) or
>>> ~(_PAGE_PSE_PAT | (_PAGE_PSE_PAT - 1) | 0ULL)
>>
>> Wouldn't it be better to just define the _PAGE_PSE bits accordingly?
>
> I don't think that's a good idea, since the flags accessors deal with
> unsigned int quantities (see {get,put}_pte_flags()), and there's no
> need to promote these to 64 bit operations. Otherwise you'd also
> have to e.g. ask for _PAGE_NX_BIT to be made 1ULL << 63 instead
> of its current 1ULL << 23.
Well, I came to my conclusion looking at the usage of _PAGE_PSE_PAT
in do_recalc() (source file arch/x86/mm/p2m-pt.c). While being fine
right now it will be a problem as soon as we support >16 TB hosts.
And finding these kind of problems might be hard.
Juergen
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next prev parent reply other threads:[~2017-03-24 7:58 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-16 16:31 [PATCH v2 0/9] Fixes to pagetable handling Andrew Cooper
2017-03-16 16:31 ` [PATCH v2 1/9] x86/cpuid: Sort cpu_has_* predicates by feature number Andrew Cooper
2017-03-17 16:08 ` Jan Beulich
2017-03-16 16:31 ` [PATCH v2 2/9] x86/pagewalk: Use pointer syntax for pfec parameter Andrew Cooper
2017-03-17 16:09 ` Jan Beulich
2017-03-20 11:29 ` George Dunlap
2017-03-23 16:28 ` Tim Deegan
2017-03-16 16:31 ` [PATCH v2 3/9] x86/shadow: Drop VALID_GFN() Andrew Cooper
2017-03-23 16:30 ` Tim Deegan
2017-03-16 16:31 ` [PATCH v2 4/9] x86/pagewalk: Clean up guest_supports_* predicates Andrew Cooper
2017-03-20 8:45 ` Jan Beulich
2017-03-20 13:36 ` Andrew Cooper
2017-03-20 13:59 ` Jan Beulich
2017-03-23 17:32 ` Andrew Cooper
2017-03-24 7:19 ` Jan Beulich
2017-03-23 16:34 ` Tim Deegan
2017-03-16 16:31 ` [PATCH v2 5/9] x86/pagewalk: Helpers for reserved bit handling Andrew Cooper
2017-03-20 8:48 ` Jan Beulich
2017-03-23 16:55 ` Tim Deegan
2017-03-23 17:02 ` Andrew Cooper
2017-03-23 17:12 ` Tim Deegan
2017-03-23 17:35 ` Andrew Cooper
2017-03-24 5:45 ` Juergen Gross
2017-03-24 7:51 ` Jan Beulich
[not found] ` <58D4DDFF0200007800147138@suse.com>
2017-03-24 7:58 ` Juergen Gross [this message]
2017-03-24 8:25 ` Jan Beulich
2017-03-24 9:06 ` Andrew Cooper
2017-03-24 7:47 ` Jan Beulich
2017-03-24 8:36 ` Andrew Cooper
2017-03-16 16:31 ` [PATCH v2 6/9] x86/pagewalk: Re-implement the pagetable walker Andrew Cooper
2017-03-16 16:31 ` [PATCH v2 7/9] x86/shadow: Use the pagewalk reserved bits helpers Andrew Cooper
2017-03-16 17:25 ` Andrew Cooper
2017-03-20 8:53 ` Jan Beulich
2017-03-23 16:57 ` Tim Deegan
2017-03-16 16:31 ` [PATCH v2 8/9] x86/pagewalk: Improve the logic behind setting access and dirty bits Andrew Cooper
2017-03-20 9:03 ` Jan Beulich
2017-03-23 17:09 ` Tim Deegan
2017-03-23 17:40 ` Andrew Cooper
2017-03-16 16:31 ` [PATCH v2 9/9] x86/pagewalk: non-functional cleanup Andrew Cooper
2017-03-20 9:04 ` Jan Beulich
2017-03-23 17:10 ` Tim Deegan
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