From: David Vrabel <david.vrabel@citrix.com>
To: Jan Beulich <JBeulich@suse.com>, David Vrabel <david.vrabel@citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCHv1] CA-201372: x86: don't flush the whole cache when changing cachability
Date: Wed, 9 Mar 2016 14:36:37 +0000 [thread overview]
Message-ID: <56E034F5.5060704@citrix.com> (raw)
In-Reply-To: <56E03AAF02000078000DADB4@prv-mh.provo.novell.com>
On 09/03/16 14:01, Jan Beulich wrote:
>>>> On 08.03.16 at 19:44, <david.vrabel@citrix.com> wrote:
>> --- a/xen/arch/x86/flushtlb.c
>> +++ b/xen/arch/x86/flushtlb.c
>> @@ -140,7 +140,8 @@ unsigned int flush_area_local(const void *va, unsigned int flags)
>> if ( order < (BITS_PER_LONG - PAGE_SHIFT) )
>> sz = 1UL << (order + PAGE_SHIFT);
>>
>> - if ( !(flags & (FLUSH_TLB|FLUSH_TLB_GLOBAL)) &&
>> + if ( (!(flags & (FLUSH_TLB|FLUSH_TLB_GLOBAL)) ||
>> + flags & FLUSH_VA_VALID) &&
>
> The & wants to be parenthesized.
Style nit-picks really should come with a patch to CODING_STYLE. The
existing code isn't consistent enough to deduce the preferred style.
>> --- a/xen/arch/x86/mm.c
>> +++ b/xen/arch/x86/mm.c
>> @@ -5641,7 +5641,7 @@ int map_pages_to_xen(
>> flush_flags |= FLUSH_TLB_GLOBAL; \
>> if ( (flags & _PAGE_PRESENT) && \
>> (((o_) ^ flags) & PAGE_CACHE_ATTRS) ) \
>> - flush_flags |= FLUSH_CACHE; \
>> + flush_flags |= FLUSH_CACHE_BY_VA; \
>> } while (0)
>
> No, that's too simple. You may flush by VA only if the MFN didn't
> change (or else you flush the wrong page).
Cachability changes goes through update_xen_mappings() which always uses
the same MFN -> virt mapping so the MFN never changes.
David
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next prev parent reply other threads:[~2016-03-09 14:37 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-08 18:44 [PATCHv1] CA-201372: x86: don't flush the whole cache when changing cachability David Vrabel
2016-03-09 13:32 ` David Vrabel
2016-03-09 14:01 ` Jan Beulich
2016-03-09 14:36 ` David Vrabel [this message]
2016-03-09 14:52 ` Jan Beulich
2016-03-09 15:23 ` Jan Beulich
2016-03-09 18:46 ` David Vrabel
2016-03-10 7:43 ` Jan Beulich
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