On Sun, Jul 06, 2008 at 12:15:56AM +0300, Avi Kivity wrote: > Marcelo Tosatti wrote: >> On Sat, Jul 05, 2008 at 08:25:30PM +0300, Avi Kivity wrote: >> >>>> @@ -1955,6 +1955,22 @@ void kvm_mmu_slot_remove_write_access(st >>>> } >>>> } >>>> +int kvm_mmu_slot_has_shadowed_page(struct kvm *kvm, int slot) >>>> +{ >>>> + struct kvm_mmu_page *sp; >>>> + int ret = 0; >>>> + >>>> + spin_lock(&kvm->mmu_lock); >>>> + list_for_each_entry(sp, &kvm->arch.active_mmu_pages, link) { >>>> + if (test_bit(slot, &sp->slot_bitmap)) { >>>> + ret = -EINVAL; >>>> + break; >>>> + } >>>> + } >>>> + spin_unlock(&kvm->mmu_lock); >>>> + return ret; >>>> +} >>>> + >>>> >>> I don't like the guest influencing host actions in this way. It's >>> just a guest. >>> >>> But I think it's unneeded. kvm_mmu_zap_page() will mark a root >>> shadow page invalid and force all vcpus to reload it, so all that's >>> needed is to keep the mmu spinlock held while removing the slot. >>> >> >> You're still keeping a shadowed page around with sp->gfn pointing to >> non-existant memslot. The code generally makes the assumption that >> gfn_to_memslot(gfn) on shadowed info will not fail. >> >> kvm_mmu_zap_page -> unaccount_shadowed, for example. >> >> > > The page has already been zapped, so we might as well > unaccount_shadowed() on the first run. It needs to be moved until after > the reload_remote_mmus() call, though.
During RH6.2 graphical installation the following oops is triggered: BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 IP: [<ffffffffa00bf172>] :kvm:gfn_to_rmap+0x3e/0x61 Pid: 4559, comm: qemu-system-x86 Not tainted The problem is that KVM allows shadow pagetable entries that point to a removed memslot to exist. In this case the cirrus vram mapping was removed, and the NULL dereference happened during kvm_set_memory_alias()'s zap_all_pages(). So nuke all shadowed pages before memslot removal. Signed-off-by: Marcelo Tosatti <[EMAIL PROTECTED]> diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c index a4cf4a2..76259da 100644 --- a/arch/ia64/kvm/kvm-ia64.c +++ b/arch/ia64/kvm/kvm-ia64.c @@ -1455,6 +1455,10 @@ int kvm_arch_set_memory_region(struct kvm *kvm, return 0; } +int kvm_arch_destroy_memory_region(struct kvm *kvm, int slot) +{ + return 0; +} long kvm_arch_dev_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index b850d24..07d69cf 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -170,6 +170,11 @@ int kvm_arch_set_memory_region(struct kvm *kvm, return 0; } +int kvm_arch_destroy_memory_region(struct kvm *kvm, int slot) +{ + return 0; +} + struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id) { struct kvm_vcpu *vcpu; diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 399acf3..201a7e1 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -675,6 +675,11 @@ int kvm_arch_set_memory_region(struct kvm *kvm, return 0; } +int kvm_arch_destroy_memory_region(struct kvm *kvm, int slot) +{ + return 0; +} + gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn) { return gfn; diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 1fd8e3b..1617b68 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -930,7 +930,7 @@ static void kvm_mmu_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp) } kvm_mmu_page_unlink_children(kvm, sp); if (!sp->root_count) { - if (!sp->role.metaphysical) + if (!sp->role.metaphysical && !sp->role.invalid) unaccount_shadowed(kvm, sp->gfn); hlist_del(&sp->hash_link); kvm_mmu_free_page(kvm, sp); @@ -938,6 +938,8 @@ static void kvm_mmu_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp) list_move(&sp->link, &kvm->arch.active_mmu_pages); sp->role.invalid = 1; kvm_reload_remote_mmus(kvm); + if (!sp->role.metaphysical) + unaccount_shadowed(kvm, sp->gfn); } kvm_mmu_reset_last_pte_updated(kvm); } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5a83c3b..8815f1d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4040,6 +4040,12 @@ int kvm_arch_set_memory_region(struct kvm *kvm, return 0; } +int kvm_arch_destroy_memory_region(struct kvm *kvm, int slot) +{ + kvm_mmu_zap_all(kvm); + return 0; +} + int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu) { return vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index d220b49..0fc7ddc 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -168,6 +168,7 @@ int kvm_arch_set_memory_region(struct kvm *kvm, struct kvm_userspace_memory_region *mem, struct kvm_memory_slot old, int user_alloc); +int kvm_arch_destroy_memory_region(struct kvm *kvm, int slot); gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn); struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn); unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index b90da0b..5ef3a5e 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -405,6 +405,12 @@ int __kvm_set_memory_region(struct kvm *kvm, if (mem->slot >= kvm->nmemslots) kvm->nmemslots = mem->slot + 1; + if (!npages) { + r = kvm_arch_destroy_memory_region(kvm, mem->slot); + if (r) + goto out_free; + } + *memslot = new; r = kvm_arch_set_memory_region(kvm, mem, old, user_alloc); -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html