51 lines
1.8 KiB
Diff
51 lines
1.8 KiB
Diff
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# Commit a15d87475ed95840dba693ab0a56d0b48a215cbc
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# Date 2013-02-21 15:16:20 +0000
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# Author Tim Deegan <tim@xen.org>
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# Committer Tim Deegan <tim@xen.org>
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x86/mm: Take the p2m lock even in shadow mode.
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The reworking of p2m lookups to use get_gfn()/put_gfn() left the
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shadow code not taking the p2m lock, even in cases where the p2m would
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be updated (i.e. PoD).
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In many cases, shadow code doesn't need the exclusion that
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get_gfn()/put_gfn() provides, as it has its own interlocks against p2m
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updates, but this is taking things too far, and can lead to crashes in
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the PoD code.
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Now that most shadow-code p2m lookups are done with explicitly
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unlocked accessors, or with the get_page_from_gfn() accessor, which is
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often lock-free, we can just turn this locking on.
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The remaining locked lookups are in sh_page_fault() (in a path that's
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almost always already serializing on the paging lock), and in
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emulate_map_dest() (which can probably be updated to use
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get_page_from_gfn()). They're not addressed here but may be in a
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follow-up patch.
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Signed-off-by: Tim Deegan <tim@xen.org>
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Acked-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
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--- a/xen/arch/x86/mm/p2m.c
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+++ b/xen/arch/x86/mm/p2m.c
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@@ -163,8 +163,7 @@ mfn_t __get_gfn_type_access(struct p2m_d
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return _mfn(gfn);
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}
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- /* For now only perform locking on hap domains */
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- if ( locked && (hap_enabled(p2m->domain)) )
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+ if ( locked )
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/* Grab the lock here, don't release until put_gfn */
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gfn_lock(p2m, gfn, 0);
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@@ -197,8 +196,7 @@ mfn_t __get_gfn_type_access(struct p2m_d
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void __put_gfn(struct p2m_domain *p2m, unsigned long gfn)
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{
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- if ( !p2m || !paging_mode_translate(p2m->domain)
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- || !hap_enabled(p2m->domain) )
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+ if ( !p2m || !paging_mode_translate(p2m->domain) )
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/* Nothing to do in this case */
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return;
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