Re: [Xen-devel] [PATCH] x86/p2m: Stop other vcpus using a nested p2m before clearing it
On 08/02/17 18:06, George Dunlap wrote: > On 08/02/17 13:20, Andrew Cooper wrote: >> On 08/02/17 13:13, Jan Beulich wrote: >> On 07.02.17 at 19:48,wrote: Until the IPI has completed, other processors might be running on this nested p2m object. clear_domain_page() does not guarantee to make 8-byte atomic updates, which means that a pagewalk on a remote processor might encounter a partial update. This is currently safe as other issues prevents a nested p2m ever being shared between two cpus (although this is contrary to the original plan). Setting p2m->np2m_base to P2M_BASE_EADDR before the IPI ensures that the IPI'd processors won't continue to use the flushed mappings. While modifying this function, remove all the trailing whitespace and tweak style in the affected areas. Signed-off-by: Andrew Cooper >>> Reviewed-by: Jan Beulich >>> but ... >>> @@ -1633,19 +1635,21 @@ p2m_flush_table(struct p2m_domain *p2m) /* This is no longer a valid nested p2m for any address space */ p2m->np2m_base = P2M_BASE_EADDR; - -/* Zap the top level of the trie */ -mfn = pagetable_get_mfn(p2m_get_pagetable(p2m)); -clear_domain_page(mfn); /* Make sure nobody else is using this p2m table */ nestedhvm_vmcx_flushtlb(p2m); +/* Zap the top level of the trie */ >>> s/trie/tree/ here, as you touch it anyway? >> >> Trie here refers to the datastructure https://en.wikipedia.org/wiki/Trie >> which is the structure implemented by processor pagetables. It is more >> specific than just calling them trees. > > Never heard that before, but we seem to already have at least six > instances in the hypervisor (and an ocaml file called 'trie.mli'), so I > guess there's precedent. :-) > > Reviewed-by: George Dunlap > > I'll check this one in. Or maybe I won't. :-) -George ___ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
Re: [Xen-devel] [PATCH] x86/p2m: Stop other vcpus using a nested p2m before clearing it
On 08/02/17 13:20, Andrew Cooper wrote: > On 08/02/17 13:13, Jan Beulich wrote: > On 07.02.17 at 19:48,wrote: >>> Until the IPI has completed, other processors might be running on this >>> nested >>> p2m object. clear_domain_page() does not guarantee to make 8-byte atomic >>> updates, which means that a pagewalk on a remote processor might encounter a >>> partial update. >>> >>> This is currently safe as other issues prevents a nested p2m ever being >>> shared >>> between two cpus (although this is contrary to the original plan). >>> >>> Setting p2m->np2m_base to P2M_BASE_EADDR before the IPI ensures that the >>> IPI'd >>> processors won't continue to use the flushed mappings. >>> >>> While modifying this function, remove all the trailing whitespace and tweak >>> style in the affected areas. >>> >>> Signed-off-by: Andrew Cooper >> Reviewed-by: Jan Beulich >> but ... >> >>> @@ -1633,19 +1635,21 @@ p2m_flush_table(struct p2m_domain *p2m) >>> >>> /* This is no longer a valid nested p2m for any address space */ >>> p2m->np2m_base = P2M_BASE_EADDR; >>> - >>> -/* Zap the top level of the trie */ >>> -mfn = pagetable_get_mfn(p2m_get_pagetable(p2m)); >>> -clear_domain_page(mfn); >>> >>> /* Make sure nobody else is using this p2m table */ >>> nestedhvm_vmcx_flushtlb(p2m); >>> >>> +/* Zap the top level of the trie */ >> s/trie/tree/ here, as you touch it anyway? > > Trie here refers to the datastructure https://en.wikipedia.org/wiki/Trie > which is the structure implemented by processor pagetables. It is more > specific than just calling them trees. Never heard that before, but we seem to already have at least six instances in the hypervisor (and an ocaml file called 'trie.mli'), so I guess there's precedent. :-) Reviewed-by: George Dunlap I'll check this one in. ___ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
Re: [Xen-devel] [PATCH] x86/p2m: Stop other vcpus using a nested p2m before clearing it
On 08/02/17 13:13, Jan Beulich wrote: On 07.02.17 at 19:48,wrote: >> Until the IPI has completed, other processors might be running on this nested >> p2m object. clear_domain_page() does not guarantee to make 8-byte atomic >> updates, which means that a pagewalk on a remote processor might encounter a >> partial update. >> >> This is currently safe as other issues prevents a nested p2m ever being >> shared >> between two cpus (although this is contrary to the original plan). >> >> Setting p2m->np2m_base to P2M_BASE_EADDR before the IPI ensures that the >> IPI'd >> processors won't continue to use the flushed mappings. >> >> While modifying this function, remove all the trailing whitespace and tweak >> style in the affected areas. >> >> Signed-off-by: Andrew Cooper > Reviewed-by: Jan Beulich > but ... > >> @@ -1633,19 +1635,21 @@ p2m_flush_table(struct p2m_domain *p2m) >> >> /* This is no longer a valid nested p2m for any address space */ >> p2m->np2m_base = P2M_BASE_EADDR; >> - >> -/* Zap the top level of the trie */ >> -mfn = pagetable_get_mfn(p2m_get_pagetable(p2m)); >> -clear_domain_page(mfn); >> >> /* Make sure nobody else is using this p2m table */ >> nestedhvm_vmcx_flushtlb(p2m); >> >> +/* Zap the top level of the trie */ > s/trie/tree/ here, as you touch it anyway? Trie here refers to the datastructure https://en.wikipedia.org/wiki/Trie which is the structure implemented by processor pagetables. It is more specific than just calling them trees. ~Andrew ___ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
Re: [Xen-devel] [PATCH] x86/p2m: Stop other vcpus using a nested p2m before clearing it
>>> On 07.02.17 at 19:48,wrote: > Until the IPI has completed, other processors might be running on this nested > p2m object. clear_domain_page() does not guarantee to make 8-byte atomic > updates, which means that a pagewalk on a remote processor might encounter a > partial update. > > This is currently safe as other issues prevents a nested p2m ever being shared > between two cpus (although this is contrary to the original plan). > > Setting p2m->np2m_base to P2M_BASE_EADDR before the IPI ensures that the IPI'd > processors won't continue to use the flushed mappings. > > While modifying this function, remove all the trailing whitespace and tweak > style in the affected areas. > > Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich but ... > @@ -1633,19 +1635,21 @@ p2m_flush_table(struct p2m_domain *p2m) > > /* This is no longer a valid nested p2m for any address space */ > p2m->np2m_base = P2M_BASE_EADDR; > - > -/* Zap the top level of the trie */ > -mfn = pagetable_get_mfn(p2m_get_pagetable(p2m)); > -clear_domain_page(mfn); > > /* Make sure nobody else is using this p2m table */ > nestedhvm_vmcx_flushtlb(p2m); > > +/* Zap the top level of the trie */ s/trie/tree/ here, as you touch it anyway? Jan ___ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
Re: [Xen-devel] [PATCH] x86/p2m: Stop other vcpus using a nested p2m before clearing it
At 18:48 + on 07 Feb (1486493293), Andrew Cooper wrote: > Until the IPI has completed, other processors might be running on this nested > p2m object. clear_domain_page() does not guarantee to make 8-byte atomic > updates, which means that a pagewalk on a remote processor might encounter a > partial update. > > This is currently safe as other issues prevents a nested p2m ever being shared > between two cpus (although this is contrary to the original plan). > > Setting p2m->np2m_base to P2M_BASE_EADDR before the IPI ensures that the IPI'd > processors won't continue to use the flushed mappings. > > While modifying this function, remove all the trailing whitespace and tweak > style in the affected areas. > > Signed-off-by: Andrew CooperReviewed-by: Tim Deegan ___ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
[Xen-devel] [PATCH] x86/p2m: Stop other vcpus using a nested p2m before clearing it
Until the IPI has completed, other processors might be running on this nested p2m object. clear_domain_page() does not guarantee to make 8-byte atomic updates, which means that a pagewalk on a remote processor might encounter a partial update. This is currently safe as other issues prevents a nested p2m ever being shared between two cpus (although this is contrary to the original plan). Setting p2m->np2m_base to P2M_BASE_EADDR before the IPI ensures that the IPI'd processors won't continue to use the flushed mappings. While modifying this function, remove all the trailing whitespace and tweak style in the affected areas. Signed-off-by: Andrew Cooper--- CC: Jan Beulich CC: Tim Deegan CC: George Dunlap --- xen/arch/x86/mm/p2m.c | 18 +++--- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c index 7675e9c..c5b1642 100644 --- a/xen/arch/x86/mm/p2m.c +++ b/xen/arch/x86/mm/p2m.c @@ -1618,8 +1618,10 @@ p2m_flush_table(struct p2m_domain *p2m) p2m_lock(p2m); -/* "Host" p2m tables can have shared entries that need a bit more - * care when discarding them */ +/* + * "Host" p2m tables can have shared entries that need a bit more care + * when discarding them. + */ ASSERT(!p2m_is_hostp2m(p2m)); /* Nested p2m's do not do pod, hence the asserts (and no pod lock)*/ ASSERT(page_list_empty(>pod.super)); @@ -1633,19 +1635,21 @@ p2m_flush_table(struct p2m_domain *p2m) /* This is no longer a valid nested p2m for any address space */ p2m->np2m_base = P2M_BASE_EADDR; - -/* Zap the top level of the trie */ -mfn = pagetable_get_mfn(p2m_get_pagetable(p2m)); -clear_domain_page(mfn); /* Make sure nobody else is using this p2m table */ nestedhvm_vmcx_flushtlb(p2m); +/* Zap the top level of the trie */ +mfn = pagetable_get_mfn(p2m_get_pagetable(p2m)); +clear_domain_page(mfn); + /* Free the rest of the trie pages back to the paging pool */ top = mfn_to_page(mfn); while ( (pg = page_list_remove_head(>pages)) ) -if ( pg != top ) +{ +if ( pg != top ) d->arch.paging.free_page(d, pg); +} page_list_add(top, >pages); p2m_unlock(p2m); -- 2.1.4 ___ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel