On Tue, 01 May 2012 11:39:36 +0200, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Sun, 2012-04-29 at 15:23 +0300, Avi Kivity wrote: > > On 04/27/2012 07:24 PM, Nikunj A. Dadhania wrote: > > > flush_tlb_others_ipi depends on lot of statics in tlb.c. Replicated > > > the flush_tlb_others_ipi as kvm_flush_tlb_others to further adapt to > > > paravirtualization. > > > > > > Use the vcpu state information inside the kvm_flush_tlb_others to > > > avoid sending ipi to pre-empted vcpus. > > > > > > * Do not send ipi's to offline vcpus and set flush_on_enter flag > > > > get_user_pages_fast() depends on the IPI to hold off page table teardown > > while they are locklessly walked with interrupts disabled. If a vcpu > > were to be preempted while in this critical section, another vcpu > > tearing down page tables would go ahead and destroy them. when the > > preempted vcpu resumes it then touches the freed pages. > > > > We could try to teach kvm and get_user_pages_fast() about this, but this > > is intrusive. Another option is to replace the cpu_relax() loop with > > something that sleeps and is then woken up by the TLB IPI handler if needed. > > I think something like > > select HAVE_RCU_TABLE_FREE if PARAVIRT > > or somesuch is just about all it takes. > [root@krm1 linux]# grep HAVE_RCU_TABLE .config CONFIG_HAVE_RCU_TABLE_FREE=y [root@krm1 linux]# make -j32 -s mm/memory.c: In function ‘tlb_remove_table_one’: mm/memory.c:315: error: implicit declaration of function ‘__tlb_remove_table’ I suppose we need to have __tlb_remove_table. Trying to understand what needs to be done there. Regards Nikunj -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
