| Message ID | 1238457604-7637-2-git-send-email-ieidus@redhat.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On Tue, Mar 31, 2009 at 03:00:02AM +0300, Izik Eidus wrote: > When using mmu notifiers, we are allowed to remove the page count > reference tooken by get_user_pages to a specific page that is mapped > inside the shadow page tables. > > This is needed so we can balance the pagecount against mapcount > checking. > > (Right now kvm increase the pagecount and does not increase the > mapcount when mapping page into shadow page table entry, > so when comparing pagecount against mapcount, you have no > reliable result.) IMO ifdef'ing CONFIG_MMU_NOTIFIERS here (and keeping the ref if unset) instead of in the backward compat code gives less room for headaches. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Marcelo Tosatti wrote: > On Tue, Mar 31, 2009 at 03:00:02AM +0300, Izik Eidus wrote: > >> When using mmu notifiers, we are allowed to remove the page count >> reference tooken by get_user_pages to a specific page that is mapped >> inside the shadow page tables. >> >> This is needed so we can balance the pagecount against mapcount >> checking. >> >> (Right now kvm increase the pagecount and does not increase the >> mapcount when mapping page into shadow page table entry, >> so when comparing pagecount against mapcount, you have no >> reliable result.) >> > > IMO ifdef'ing CONFIG_MMU_NOTIFIERS here (and keeping the ref if unset) > instead of in the backward compat code gives less room for headaches. > > That was the first version of this patch, Avi preferred not to do it... -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Izik Eidus wrote: > Marcelo Tosatti wrote: >> On Tue, Mar 31, 2009 at 03:00:02AM +0300, Izik Eidus wrote: >> >>> When using mmu notifiers, we are allowed to remove the page count >>> reference tooken by get_user_pages to a specific page that is mapped >>> inside the shadow page tables. >>> >>> This is needed so we can balance the pagecount against mapcount >>> checking. >>> >>> (Right now kvm increase the pagecount and does not increase the >>> mapcount when mapping page into shadow page table entry, >>> so when comparing pagecount against mapcount, you have no >>> reliable result.) >>> >> >> IMO ifdef'ing CONFIG_MMU_NOTIFIERS here (and keeping the ref if unset) >> instead of in the backward compat code gives less room for headaches. >> >> > That was the first version of this patch, Avi preferred not to do it... > Avi, You mind if i changed it to use the IFDEF ? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Izik Eidus wrote: > Izik Eidus wrote: >> Marcelo Tosatti wrote: >>> On Tue, Mar 31, 2009 at 03:00:02AM +0300, Izik Eidus wrote: >>> >>>> When using mmu notifiers, we are allowed to remove the page count >>>> reference tooken by get_user_pages to a specific page that is mapped >>>> inside the shadow page tables. >>>> >>>> This is needed so we can balance the pagecount against mapcount >>>> checking. >>>> >>>> (Right now kvm increase the pagecount and does not increase the >>>> mapcount when mapping page into shadow page table entry, >>>> so when comparing pagecount against mapcount, you have no >>>> reliable result.) >>>> >>> >>> IMO ifdef'ing CONFIG_MMU_NOTIFIERS here (and keeping the ref if unset) >>> instead of in the backward compat code gives less room for headaches. >>> >>> >> That was the first version of this patch, Avi preferred not to do it... >> > Avi, You mind if i changed it to use the IFDEF ? No, let's not have too many ifdefs in the code. I'll hack it in hack-module.awk.
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index b625ed4..df8fbaf 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -567,9 +567,7 @@ static void rmap_remove(struct kvm *kvm, u64 *spte) if (*spte & shadow_accessed_mask) kvm_set_pfn_accessed(pfn); if (is_writeble_pte(*spte)) - kvm_release_pfn_dirty(pfn); - else - kvm_release_pfn_clean(pfn); + kvm_set_pfn_dirty(pfn); rmapp = gfn_to_rmap(kvm, sp->gfns[spte - sp->spt], is_large_pte(*spte)); if (!*rmapp) { printk(KERN_ERR "rmap_remove: %p %llx 0->BUG\n", spte, *spte); @@ -1812,8 +1810,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte, page_header_update_slot(vcpu->kvm, shadow_pte, gfn); if (!was_rmapped) { rmap_add(vcpu, shadow_pte, gfn, largepage); - if (!is_rmap_pte(*shadow_pte)) - kvm_release_pfn_clean(pfn); + kvm_release_pfn_clean(pfn); } else { if (was_writeble) kvm_release_pfn_dirty(pfn);
When using mmu notifiers, we are allowed to remove the page count reference tooken by get_user_pages to a specific page that is mapped inside the shadow page tables. This is needed so we can balance the pagecount against mapcount checking. (Right now kvm increase the pagecount and does not increase the mapcount when mapping page into shadow page table entry, so when comparing pagecount against mapcount, you have no reliable result.) Signed-off-by: Izik Eidus <ieidus@redhat.com> --- arch/x86/kvm/mmu.c | 7 ++----- 1 files changed, 2 insertions(+), 5 deletions(-)