diff options
author | Tim Deegan <tim@xen.org> | 2013-02-21 17:41:26 +0000 |
---|---|---|
committer | Tim Deegan <tim@xen.org> | 2013-02-21 17:41:34 +0000 |
commit | 7f05d3ff7692574f40d0b337d767a216f347dcdb (patch) | |
tree | 2016807d750cc6295515d8763c2a223acec680e4 /xen/arch/x86/mm | |
parent | 1ac127193dafb4b5a303e1b0180188141509df3e (diff) | |
download | xen-7f05d3ff7692574f40d0b337d767a216f347dcdb.tar.gz xen-7f05d3ff7692574f40d0b337d767a216f347dcdb.tar.bz2 xen-7f05d3ff7692574f40d0b337d767a216f347dcdb.zip |
x86/mm: avoid locked lookups in shadow emulation.
Use get_page_from_gfn() instead of get_gfn(), avoiding taking the p2m
lock in the common case.
Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Acked-by: Tim Deegan <tim@xen.org>
Diffstat (limited to 'xen/arch/x86/mm')
-rw-r--r-- | xen/arch/x86/mm/shadow/multi.c | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c index f7181b7904..68f5505a4e 100644 --- a/xen/arch/x86/mm/shadow/multi.c +++ b/xen/arch/x86/mm/shadow/multi.c @@ -4564,6 +4564,7 @@ static mfn_t emulate_gva_to_mfn(struct vcpu *v, struct sh_emulate_ctxt *sh_ctxt) { unsigned long gfn; + struct page_info *page; mfn_t mfn; p2m_type_t p2mt; uint32_t pfec = PFEC_page_present | PFEC_write_access; @@ -4581,22 +4582,31 @@ static mfn_t emulate_gva_to_mfn(struct vcpu *v, /* Translate the GFN to an MFN */ ASSERT(!paging_locked_by_me(v->domain)); - mfn = get_gfn(v->domain, _gfn(gfn), &p2mt); - + + page = get_page_from_gfn(v->domain, gfn, &p2mt, P2M_ALLOC); + + /* Sanity checking */ + if ( page == NULL ) + { + return _mfn(BAD_GFN_TO_MFN); + } if ( p2m_is_readonly(p2mt) ) { - put_gfn(v->domain, gfn); + put_page(page); return _mfn(READONLY_GFN); } if ( !p2m_is_ram(p2mt) ) { - put_gfn(v->domain, gfn); + put_page(page); return _mfn(BAD_GFN_TO_MFN); } - + mfn = page_to_mfn(page); ASSERT(mfn_valid(mfn)); + v->arch.paging.last_write_was_pt = !!sh_mfn_is_a_page_table(mfn); - put_gfn(v->domain, gfn); + /* Note shadow cannot page out or unshare this mfn, so the map won't + * disappear. Otherwise, caller must hold onto page until done. */ + put_page(page); return mfn; } |