From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] kvm: Delete the slot only when KVM_MEM_READONLY flag is changed Date: Tue, 12 Jun 2018 14:17:27 +0200 Message-ID: <25094a6a-df4e-3dbb-ef69-e478edb46ff3@redhat.com> References: <1526462314-19720-1-git-send-email-zhaoshenglong@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: shannon.zhaosl@gmail.com, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org To: Shannon Zhao , qemu-devel@nongnu.org, guangrong.xiao@gmail.com Return-path: In-Reply-To: <1526462314-19720-1-git-send-email-zhaoshenglong@huawei.com> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org On 16/05/2018 11:18, Shannon Zhao wrote: > According to KVM commit 75d61fbc, it needs to delete the slot before > changing the KVM_MEM_READONLY flag. But QEMU commit 235e8982 only check > whether KVM_MEM_READONLY flag is set instead of changing. It doesn't > need to delete the slot if the KVM_MEM_READONLY flag is not changed. > > This fixes a issue that migrating a VM at the OVMF startup stage and > VM is executing the codes in rom. Between the deleting and adding the > slot in kvm_set_user_memory_region, there is a chance that guest access > rom and trap to KVM, then KVM can't find the corresponding memslot. > While KVM (on ARM) injects an abort to guest due to the broken hva, then > guest will get stuck. > > Signed-off-by: Shannon Zhao I'm a bit worried about old_flags not being set on all paths to kvm_set_user_memory_region. This would lead to extra KVM_SET_USER_MEMORY_REGION calls. It should not be a problem but it is ugly. Does something like the additional changes below work for you? Thanks, Paolo diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index b04f193a76..e318bcfb78 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -257,7 +257,7 @@ int kvm_physical_memory_addr_from_host(KVMState *s, void *ram, return 0; } -static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot) +static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot, bool new) { KVMState *s = kvm_state; struct kvm_userspace_memory_region mem; @@ -268,7 +268,7 @@ static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot) mem.userspace_addr = (unsigned long)slot->ram; mem.flags = slot->flags; - if (slot->memory_size && (mem.flags ^ slot->old_flags) & KVM_MEM_READONLY) { + if (slot->memory_size && !new && (mem.flags ^ slot->old_flags) & KVM_MEM_READONLY) { /* Set the slot size to 0 before setting the slot to the desired * value. This is needed based on KVM commit 75d61fbc. */ mem.memory_size = 0; @@ -276,6 +276,7 @@ static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot) } mem.memory_size = slot->memory_size; ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem); + slot->old_flags = mem.flags; trace_kvm_set_user_memory(mem.slot, mem.flags, mem.guest_phys_addr, mem.memory_size, mem.userspace_addr, ret); return ret; @@ -394,7 +395,6 @@ static int kvm_slot_update_flags(KVMMemoryListener *kml, KVMSlot *mem, { int old_flags; - mem->old_flags = mem->flags; mem->flags = kvm_mem_flags(mr); /* If nothing changed effectively, no need to issue ioctl */ @@ -402,7 +402,7 @@ static int kvm_slot_update_flags(KVMMemoryListener *kml, KVMSlot *mem, return 0; } - return kvm_set_user_memory_region(kml, mem); + return kvm_set_user_memory_region(kml, mem, false); } static int kvm_section_update_flags(KVMMemoryListener *kml, @@ -756,7 +756,8 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml, /* unregister the slot */ mem->memory_size = 0; - err = kvm_set_user_memory_region(kml, mem); + mem->flags = 0; + err = kvm_set_user_memory_region(kml, mem, false); if (err) { fprintf(stderr, "%s: error unregistering slot: %s\n", __func__, strerror(-err)); @@ -772,7 +773,7 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml, mem->ram = ram; mem->flags = kvm_mem_flags(mr); - err = kvm_set_user_memory_region(kml, mem); + err = kvm_set_user_memory_region(kml, mem, true); if (err) { fprintf(stderr, "%s: error registering slot: %s\n", __func__, strerror(-err)); From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40630) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fSiEx-0002IU-67 for qemu-devel@nongnu.org; Tue, 12 Jun 2018 08:17:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fSiEu-0003kB-09 for qemu-devel@nongnu.org; Tue, 12 Jun 2018 08:17:35 -0400 Received: from mail-wr0-x243.google.com ([2a00:1450:400c:c0c::243]:45257) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fSiEt-0003jp-Mj for qemu-devel@nongnu.org; Tue, 12 Jun 2018 08:17:31 -0400 Received: by mail-wr0-x243.google.com with SMTP id o12-v6so23825639wrm.12 for ; Tue, 12 Jun 2018 05:17:31 -0700 (PDT) Sender: Paolo Bonzini References: <1526462314-19720-1-git-send-email-zhaoshenglong@huawei.com> From: Paolo Bonzini Message-ID: <25094a6a-df4e-3dbb-ef69-e478edb46ff3@redhat.com> Date: Tue, 12 Jun 2018 14:17:27 +0200 MIME-Version: 1.0 In-Reply-To: <1526462314-19720-1-git-send-email-zhaoshenglong@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] kvm: Delete the slot only when KVM_MEM_READONLY flag is changed List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Shannon Zhao , qemu-devel@nongnu.org, guangrong.xiao@gmail.com Cc: kvmarm@lists.cs.columbia.edu, shannon.zhaosl@gmail.com, kvm@vger.kernel.org, zhengxiang9@huawei.com On 16/05/2018 11:18, Shannon Zhao wrote: > According to KVM commit 75d61fbc, it needs to delete the slot before > changing the KVM_MEM_READONLY flag. But QEMU commit 235e8982 only check > whether KVM_MEM_READONLY flag is set instead of changing. It doesn't > need to delete the slot if the KVM_MEM_READONLY flag is not changed. > > This fixes a issue that migrating a VM at the OVMF startup stage and > VM is executing the codes in rom. Between the deleting and adding the > slot in kvm_set_user_memory_region, there is a chance that guest access > rom and trap to KVM, then KVM can't find the corresponding memslot. > While KVM (on ARM) injects an abort to guest due to the broken hva, then > guest will get stuck. > > Signed-off-by: Shannon Zhao I'm a bit worried about old_flags not being set on all paths to kvm_set_user_memory_region. This would lead to extra KVM_SET_USER_MEMORY_REGION calls. It should not be a problem but it is ugly. Does something like the additional changes below work for you? Thanks, Paolo diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index b04f193a76..e318bcfb78 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -257,7 +257,7 @@ int kvm_physical_memory_addr_from_host(KVMState *s, void *ram, return 0; } -static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot) +static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot, bool new) { KVMState *s = kvm_state; struct kvm_userspace_memory_region mem; @@ -268,7 +268,7 @@ static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot) mem.userspace_addr = (unsigned long)slot->ram; mem.flags = slot->flags; - if (slot->memory_size && (mem.flags ^ slot->old_flags) & KVM_MEM_READONLY) { + if (slot->memory_size && !new && (mem.flags ^ slot->old_flags) & KVM_MEM_READONLY) { /* Set the slot size to 0 before setting the slot to the desired * value. This is needed based on KVM commit 75d61fbc. */ mem.memory_size = 0; @@ -276,6 +276,7 @@ static int kvm_set_user_memory_region(KVMMemoryListener *kml, KVMSlot *slot) } mem.memory_size = slot->memory_size; ret = kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem); + slot->old_flags = mem.flags; trace_kvm_set_user_memory(mem.slot, mem.flags, mem.guest_phys_addr, mem.memory_size, mem.userspace_addr, ret); return ret; @@ -394,7 +395,6 @@ static int kvm_slot_update_flags(KVMMemoryListener *kml, KVMSlot *mem, { int old_flags; - mem->old_flags = mem->flags; mem->flags = kvm_mem_flags(mr); /* If nothing changed effectively, no need to issue ioctl */ @@ -402,7 +402,7 @@ static int kvm_slot_update_flags(KVMMemoryListener *kml, KVMSlot *mem, return 0; } - return kvm_set_user_memory_region(kml, mem); + return kvm_set_user_memory_region(kml, mem, false); } static int kvm_section_update_flags(KVMMemoryListener *kml, @@ -756,7 +756,8 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml, /* unregister the slot */ mem->memory_size = 0; - err = kvm_set_user_memory_region(kml, mem); + mem->flags = 0; + err = kvm_set_user_memory_region(kml, mem, false); if (err) { fprintf(stderr, "%s: error unregistering slot: %s\n", __func__, strerror(-err)); @@ -772,7 +773,7 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml, mem->ram = ram; mem->flags = kvm_mem_flags(mr); - err = kvm_set_user_memory_region(kml, mem); + err = kvm_set_user_memory_region(kml, mem, true); if (err) { fprintf(stderr, "%s: error registering slot: %s\n", __func__, strerror(-err));