Re: cr3 OOS optimisation breaks 32-bit GNU/kFreeBSD guest

Aurelien Jarno
2009-03-24T10:39:09Z

On Mon, Mar 23, 2009 at 02:27:25PM -0300, Marcelo Tosatti wrote:
> On Sun, Mar 22, 2009 at 11:35:00AM +0200, Avi Kivity wrote:
> > Good catch, indeed. But is it sufficient? We could unlink a page
> > through other means, for example by the guest zapping a page directory
> > entry.
>
> Yep.
>
> > Maybe it's best to resync when relinking a global page?
>
> How about this. It will shorten the unsync period of global pages,
> unfortunately.

JFYI, it still fixes the problem seen with FreeBSD.

> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 2a36f7f..bccdcc7 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -1238,6 +1238,10 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> set_bit(KVM_REQ_MMU_SYNC, &vcpu->requests);
> kvm_mmu_mark_parents_unsync(vcpu, sp);
> }
> + if (role.level != PT_PAGE_TABLE_LEVEL &&
> + !list_empty(&vcpu->kvm->arch.oos_global_pages))
> + set_bit(KVM_REQ_MMU_GLOBAL_SYNC, &vcpu->requests);
> +
> pgprintk("%s: found\n", __func__);
> return sp;
> }
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 2ea8262..48169d7 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3109,6 +3109,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> kvm_write_guest_time(vcpu);
> if (test_and_clear_bit(KVM_REQ_MMU_SYNC, &vcpu->requests))
> kvm_mmu_sync_roots(vcpu);
> + if (test_and_clear_bit(KVM_REQ_MMU_GLOBAL_SYNC, &vcpu->requests))
> + kvm_mmu_sync_global(vcpu);
> if (test_and_clear_bit(KVM_REQ_TLB_FLUSH, &vcpu->requests))
> kvm_x86_ops->tlb_flush(vcpu);
> if (test_and_clear_bit(KVM_REQ_REPORT_TPR_ACCESS,
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 11eb702..8efd6e3 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -37,7 +37,8 @@
> #define KVM_REQ_PENDING_TIMER 5
> #define KVM_REQ_UNHALT 6
> #define KVM_REQ_MMU_SYNC 7
> -#define KVM_REQ_KVMCLOCK_UPDATE 8
> +#define KVM_REQ_MMU_GLOBAL_SYNC 8
> +#define KVM_REQ_KVMCLOCK_UPDATE 9
>
> #define KVM_USERSPACE_IRQ_SOURCE_ID 0
>
>

--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurelien@aurel32.net http://www.aurel32.net