On Wed, Apr 27, 2016 at 9:31 AM, George Dunlap <george.dun...@citrix.com> wrote:
> On 27/04/16 16:18, Tamas K Lengyel wrote: > > On Wed, Apr 27, 2016 at 9:01 AM, George Dunlap <george.dun...@citrix.com > > > > wrote: > > > >> On 21/04/16 18:10, Tamas K Lengyel wrote: > >>> Don't propagate altp2m changes from ept_set_entry for memshare as > >> memshare > >>> already has the lock. We call altp2m propagate changes once memshare > >>> successfully finishes. Also, allow the hostp2m entries to be of type > >>> p2m_ram_shared. > >>> > >>> Signed-off-by: Tamas K Lengyel <ta...@tklengyel.com> > >> > >> Sorry for the delay in reviewing -- trying to get my head back around > >> the altp2m code. On the whole looks reasonable, but one question... > >> > >>> --- > >>> Cc: George Dunlap <george.dun...@eu.citrix.com> > >>> Cc: Keir Fraser <k...@xen.org> > >>> Cc: Jan Beulich <jbeul...@suse.com> > >>> Cc: Andrew Cooper <andrew.coop...@citrix.com> > >>> Cc: Jun Nakajima <jun.nakaj...@intel.com> > >>> Cc: Kevin Tian <kevin.t...@intel.com> > >>> --- > >>> xen/arch/x86/mm/mem_sharing.c | 11 +++++++++++ > >>> xen/arch/x86/mm/p2m-ept.c | 2 +- > >>> xen/arch/x86/mm/p2m.c | 7 +++---- > >>> 3 files changed, 15 insertions(+), 5 deletions(-) > >>> > >>> diff --git a/xen/arch/x86/mm/mem_sharing.c > >> b/xen/arch/x86/mm/mem_sharing.c > >>> index a522423..d5b4b2d 100644 > >>> --- a/xen/arch/x86/mm/mem_sharing.c > >>> +++ b/xen/arch/x86/mm/mem_sharing.c > >>> @@ -35,6 +35,7 @@ > >>> #include <asm/p2m.h> > >>> #include <asm/atomic.h> > >>> #include <asm/event.h> > >>> +#include <asm/altp2m.h> > >>> #include <xsm/xsm.h> > >>> > >>> #include "mm-locks.h" > >>> @@ -1026,6 +1027,16 @@ int mem_sharing_share_pages(struct domain *sd, > >> unsigned long sgfn, shr_handle_t > >>> /* We managed to free a domain page. */ > >>> atomic_dec(&nr_shared_mfns); > >>> atomic_inc(&nr_saved_mfns); > >>> + > >>> + if( altp2m_active(cd) ) > >>> + { > >>> + p2m_access_t a; > >>> + struct p2m_domain *p2m = p2m_get_hostp2m(cd); > >>> + p2m->get_entry(p2m, cgfn, NULL, &a, 0, NULL, NULL); > >>> + p2m_altp2m_propagate_change(cd, _gfn(cgfn), smfn, > PAGE_ORDER_4K, > >>> + p2m_ram_shared, a); > >>> + } > >>> + > >>> ret = 0; > >>> > >>> err_out: > >>> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c > >>> index 3cb6868..1ac3018 100644 > >>> --- a/xen/arch/x86/mm/p2m-ept.c > >>> +++ b/xen/arch/x86/mm/p2m-ept.c > >>> @@ -846,7 +846,7 @@ out: > >>> if ( is_epte_present(&old_entry) ) > >>> ept_free_entry(p2m, &old_entry, target); > >>> > >>> - if ( rc == 0 && p2m_is_hostp2m(p2m) ) > >>> + if ( rc == 0 && p2m_is_hostp2m(p2m) && p2mt != p2m_ram_shared ) > >>> p2m_altp2m_propagate_change(d, _gfn(gfn), mfn, order, p2mt, > >> p2ma); > >>> > >>> return rc; > >>> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c > >>> index b3fce1b..d2aebf7 100644 > >>> --- a/xen/arch/x86/mm/p2m.c > >>> +++ b/xen/arch/x86/mm/p2m.c > >>> @@ -1739,11 +1739,10 @@ int p2m_set_altp2m_mem_access(struct domain *d, > >> struct p2m_domain *hp2m, > >>> /* Check host p2m if no valid entry in alternate */ > >>> if ( !mfn_valid(mfn) ) > >>> { > >>> - mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a, > >>> - P2M_ALLOC | P2M_UNSHARE, &page_order, > >> NULL); > >>> + mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a, 0, &page_order, > >> NULL); > >> > >> Why are you getting rid of P2M_ALLOC here? What happens if the hp2m > >> entry is populate-on-demand? > >> > > > > There is a check further down here that only allows p2m_ram_rw and > > p2m_ram_shared. > > So what P2M_ALLOC means is, "If this is entry is PoD, then please > populate it so I get a ram page." So the only way you can get a > p2m_populate_on_demand type returned is if you remove this flag. Leave > it and (assuming there's enough ram to go around), you'll always get > p2m_ram_rw. :-) > > > On the non-altp2m path mem_access doesn't request P2M_ALLOC > > either (but doesn't check the type), so I would say mem_access is not > > compatible with PoD. > > Off the top of my head I can't see a reason why they couldn't co-exist > in principle, if you added P2M_ALLOC in a few key places. > Sure, I just rather do that in a separate patch and for now have the mem_access paths behaving the same way before doing that adjustment. Tamas
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