Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752431AbYKRBF1 (ORCPT ); Mon, 17 Nov 2008 20:05:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751948AbYKRBFN (ORCPT ); Mon, 17 Nov 2008 20:05:13 -0500 Received: from mx2.redhat.com ([66.187.237.31]:60680 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751823AbYKRBFL (ORCPT ); Mon, 17 Nov 2008 20:05:11 -0500 From: Glauber Costa To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, avi@redhat.com Subject: [PATCH] Check for ambiguities in create alias ioctl. Date: Tue, 18 Nov 2008 01:01:18 -0200 Message-Id: <1226977278-5523-1-git-send-email-glommer@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5990 Lines: 200 The current alias ioctl allows for the creation of an alias covering a gpa that already exists. It is invalid, because the gpa space needs to be uniquely mapped. So, if there's a memory slot covering gpa range 0x123000 to 0x124000, and we create an alias from any gpa within that range to a different target, we create an essential ambiguity that brings no value at the cost of a lot of confusion. Right now this confusion manifests itself as a BUG() triggered in the rmaps code path. Signed-off-by: Glauber Costa --- arch/ia64/kvm/kvm-ia64.c | 6 ++++++ arch/powerpc/kvm/powerpc.c | 5 +++++ arch/s390/kvm/kvm-s390.c | 6 ++++++ arch/x86/kvm/x86.c | 23 +++++++++++++++++++++-- include/linux/kvm_host.h | 4 ++++ virt/kvm/kvm_main.c | 31 ++++++++++++++++++++----------- 6 files changed, 62 insertions(+), 13 deletions(-) diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c index af1464f..7e9d796 100644 --- a/arch/ia64/kvm/kvm-ia64.c +++ b/arch/ia64/kvm/kvm-ia64.c @@ -1695,6 +1695,12 @@ void kvm_arch_hardware_unsetup(void) { } +int kvm_arch_check_overlap(struct kvm *kvm, gfn_t base_gfn, + unsigned long npages, void *me) +{ + return 0; +} + static void vcpu_kick_intr(void *info) { #ifdef DEBUG diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index 90a6fc4..a0c164e 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -45,6 +45,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v) return !(v->arch.msr & MSR_WE); } +int kvm_arch_check_overlap(struct kvm *kvm, gfn_t base_gfn, + unsigned long npages, void *me) +{ + return 0; +} int kvmppc_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu) { diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 8b00eb2..780f33e 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -101,6 +101,12 @@ void kvm_arch_exit(void) { } +int kvm_arch_check_overlap(struct kvm *kvm, gfn_t base_gfn, + unsigned long npages, void *me) +{ + return 0; +} + /* Section: device related */ long kvm_arch_dev_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index f1f8ff2..324af5e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1506,6 +1506,22 @@ gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn) return gfn; } +int kvm_arch_check_overlap(struct kvm *kvm, gfn_t base_gfn, + unsigned long npages, void *me) +{ + int i; + for (i = 0; i < kvm->arch.naliases ; i++) { + struct kvm_mem_alias *p = &kvm->arch.aliases[i]; + if (p == me) + continue; + + if (!((base_gfn + npages < p->base_gfn) || + (base_gfn > p->base_gfn + p->npages))) + return -EEXIST; + } + return 0; +} + /* * Set a new alias region. Aliases map a portion of physical memory into * another portion. This is useful for memory windows, for example the PC @@ -1540,18 +1556,21 @@ static int kvm_vm_ioctl_set_memory_alias(struct kvm *kvm, p->npages = alias->memory_size >> PAGE_SHIFT; p->target_gfn = alias->target_phys_addr >> PAGE_SHIFT; + r = kvm_check_overlap(kvm, p->base_gfn, p->npages, p); + if (r) + goto out_locked; + for (n = KVM_ALIAS_SLOTS; n > 0; --n) if (kvm->arch.aliases[n - 1].npages) break; kvm->arch.naliases = n; +out_locked: spin_unlock(&kvm->mmu_lock); kvm_mmu_zap_all(kvm); up_write(&kvm->slots_lock); - return 0; - out: return r; } diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index bb92be2..79f34ab 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -178,6 +178,10 @@ 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_check_overlap(struct kvm *kvm, gfn_t base_gfn, + unsigned long pages, void *me); +int kvm_arch_check_overlap(struct kvm *kvm, gfn_t base_gfn, + unsigned long pages, void *me); void kvm_arch_flush_shadow(struct kvm *kvm); gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn); struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fd265b2..18af322 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -685,6 +685,23 @@ static int kvm_vm_release(struct inode *inode, struct file *filp) return 0; } +int kvm_check_overlap(struct kvm *kvm, gfn_t base_gfn, + unsigned long npages, void *me) +{ + int i; + + for (i = 0; i < KVM_MEMORY_SLOTS; ++i) { + struct kvm_memory_slot *s = &kvm->memslots[i]; + + if (s == me) + continue; + if (!((base_gfn + npages <= s->base_gfn) || + (base_gfn >= s->base_gfn + s->npages))) + return -EEXIST; + } + return kvm_arch_check_overlap(kvm, base_gfn, npages, me); +} + /* * Allocate some memory and give it an address in the guest physical address * space. @@ -700,7 +717,6 @@ int __kvm_set_memory_region(struct kvm *kvm, int r; gfn_t base_gfn; unsigned long npages; - unsigned long i; struct kvm_memory_slot *memslot; struct kvm_memory_slot old, new; @@ -733,17 +749,10 @@ int __kvm_set_memory_region(struct kvm *kvm, if (npages && old.npages && npages != old.npages) goto out_free; - /* Check for overlaps */ - r = -EEXIST; - for (i = 0; i < KVM_MEMORY_SLOTS; ++i) { - struct kvm_memory_slot *s = &kvm->memslots[i]; + r = kvm_check_overlap(kvm, base_gfn, npages, memslot); + if (r) + goto out_free; - if (s == memslot) - continue; - if (!((base_gfn + npages <= s->base_gfn) || - (base_gfn >= s->base_gfn + s->npages))) - goto out_free; - } /* Free page dirty bitmap if unneeded */ if (!(new.flags & KVM_MEM_LOG_DIRTY_PAGES)) -- 1.5.6.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/