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Sun, 30 Oct 2022 19:30:51 -0700 (PDT) Received: from redhat.com ([38.15.36.239]) by smtp.gmail.com with ESMTPSA id j127-20020a026385000000b00375147442f3sm2281584jac.16.2022.10.30.19.30.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 30 Oct 2022 19:30:50 -0700 (PDT) Date: Sun, 30 Oct 2022 20:30:48 -0600 From: Alex Williamson To: Cindy Lu Cc: jasowang@redhat.com, mst@redhat.com, pbonzini@redhat.com, peterx@redhat.com, david@redhat.com, f4bug@amsat.org, sgarzare@redhat.com, qemu-devel@nongnu.org Subject: Re: [PATCH v8 1/2] vfio: move implement of vfio_get_xlat_addr() to memory.c Message-ID: <20221030203048.3f557509.alex.williamson@redhat.com> In-Reply-To: <20221031015605.1396243-2-lulu@redhat.com> References: <20221031015605.1396243-1-lulu@redhat.com> <20221031015605.1396243-2-lulu@redhat.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=170.10.133.124; envelope-from=alex.williamson@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.055, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Qemu-devel" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, 31 Oct 2022 09:56:04 +0800 Cindy Lu wrote: > - Move the implement vfio_get_xlat_addr to softmmu/memory.c, and > =C2=A0 change the name to memory_get_xlat_addr(). So we can use this > =C2=A0 function on other devices, such as vDPA device. > - Add a new function vfio_get_xlat_addr in vfio/common.c, and it will che= ck > whether the memory is backed by a discard manager. the device can > have its own warning. >=20 > Signed-off-by: Cindy Lu > --- > hw/vfio/common.c | 101 +++++++++++------------------------------- > include/exec/memory.h | 4 ++ > softmmu/memory.c | 72 ++++++++++++++++++++++++++++++ > 3 files changed, 102 insertions(+), 75 deletions(-) Some changes I'd like to see below, but otherwise Acked-by: Alex Williamson >=20 > diff --git a/hw/vfio/common.c b/hw/vfio/common.c > index ace9562a9b..5bfd55de86 100644 > --- a/hw/vfio/common.c > +++ b/hw/vfio/common.c > @@ -578,86 +578,37 @@ static bool vfio_listener_skipped_section(MemoryReg= ionSection *section) > static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr, > ram_addr_t *ram_addr, bool *read_only) > { > - MemoryRegion *mr; > - hwaddr xlat; > - hwaddr len =3D iotlb->addr_mask + 1; > - bool writable =3D iotlb->perm & IOMMU_WO; > - > - /* > - * The IOMMU TLB entry we have just covers translation through > - * this IOMMU to its immediate target. We need to translate > - * it the rest of the way through to memory. > - */ > - mr =3D address_space_translate(&address_space_memory, > - iotlb->translated_addr, > - &xlat, &len, writable, > - MEMTXATTRS_UNSPECIFIED); > - if (!memory_region_is_ram(mr)) { > - error_report("iommu map to non memory area %"HWADDR_PRIx"", > - xlat); > - return false; > - } else if (memory_region_has_ram_discard_manager(mr)) { > - RamDiscardManager *rdm =3D memory_region_get_ram_discard_manager= (mr); > - MemoryRegionSection tmp =3D { > - .mr =3D mr, > - .offset_within_region =3D xlat, > - .size =3D int128_make64(len), > - }; > - > + bool mr_has_discard_manager; > + if (memory_get_xlat_addr(iotlb, vaddr, ram_addr, read_only, > + &mr_has_discard_manager)) { > /* > - * Malicious VMs can map memory into the IOMMU, which is expected > - * to remain discarded. vfio will pin all pages, populating memo= ry. > - * Disallow that. vmstate priorities make sure any RamDiscardMan= ager > - * were already restored before IOMMUs are restored. > + * if the mr has the discard_manager and the return value of > + * memory_get_xlat_addr() is ture then we need to warn s/ture/true/ But then the comment below is really describing why we're generating a warning, so the above additional comment is mostly just noise. I'd also prefer to see this as: { bool ret, mr_has_discard_manager; ret =3D memory_get_xlat_addr(iotlb, vaddr, ram_addr, read_only, &mr_has_discard_manager)); if (ret && mr_has_discard_manager) { // Unmodified comment and warn report from existing code } return ret; } > */ > - if (!ram_discard_manager_is_populated(rdm, &tmp)) { > - error_report("iommu map to discarded memory (e.g., unplugged= via" > - " virtio-mem): %"HWADDR_PRIx"", > - iotlb->translated_addr); > - return false; > + if (mr_has_discard_manager) { > + /* > + * Malicious VMs might trigger discarding of IOMMU-mapped me= mory. > + * The pages will remain pinned inside vfio until unmapped, > + * resulting in a higher memory consumption than expected. I= f memory > + * would get populated again later, there would be an incons= istency > + * between pages pinned by vfio and pages seen by QEMU. This= is the > + * case until unmapped from the IOMMU (e.g., during device r= eset). > + * > + * With malicious guests, we really only care about pinning = more > + * memory than expected. RLIMIT_MEMLOCK set for the user/pro= cess can > + * never be exceeded and can be used to mitigate this proble= m. > + */ > + warn_report_once( > + "Using vfio with vIOMMUs and coordinated discarding of" > + " RAM (e.g., virtio-mem) works, however, malicious" > + " guests can trigger pinning of more memory than" > + " intended via an IOMMU. It's possible to mitigate " > + " by setting/adjusting RLIMIT_MEMLOCK."); > } > =20 > - /* > - * Malicious VMs might trigger discarding of IOMMU-mapped memory= . The > - * pages will remain pinned inside vfio until unmapped, resultin= g in a > - * higher memory consumption than expected. If memory would get > - * populated again later, there would be an inconsistency betwee= n pages > - * pinned by vfio and pages seen by QEMU. This is the case until > - * unmapped from the IOMMU (e.g., during device reset). > - * > - * With malicious guests, we really only care about pinning more= memory > - * than expected. RLIMIT_MEMLOCK set for the user/process can ne= ver be > - * exceeded and can be used to mitigate this problem. > - */ > - warn_report_once("Using vfio with vIOMMUs and coordinated discar= ding of" > - " RAM (e.g., virtio-mem) works, however, malici= ous" > - " guests can trigger pinning of more memory tha= n" > - " intended via an IOMMU. It's possible to mitig= ate " > - " by setting/adjusting RLIMIT_MEMLOCK."); > - } > - > - /* > - * Translation truncates length to the IOMMU page size, > - * check that it did not truncate too much. > - */ > - if (len & iotlb->addr_mask) { > - error_report("iommu has granularity incompatible with target AS"= ); > - return false; > - } > - > - if (vaddr) { > - *vaddr =3D memory_region_get_ram_ptr(mr) + xlat; > + return true; > } > - > - if (ram_addr) { > - *ram_addr =3D memory_region_get_ram_addr(mr) + xlat; > - } > - > - if (read_only) { > - *read_only =3D !writable || mr->readonly; > - } > - > - return true; > + return false; > } > =20 > static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb) > diff --git a/include/exec/memory.h b/include/exec/memory.h > index bfb1de8eea..d1e79c39dc 100644 > --- a/include/exec/memory.h > +++ b/include/exec/memory.h > @@ -713,6 +713,10 @@ void ram_discard_manager_register_listener(RamDiscar= dManager *rdm, > void ram_discard_manager_unregister_listener(RamDiscardManager *rdm, > RamDiscardListener *rdl); > =20 > +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr, > + ram_addr_t *ram_addr, bool *read_only, > + bool *mr_has_discard_manager); > + > typedef struct CoalescedMemoryRange CoalescedMemoryRange; > typedef struct MemoryRegionIoeventfd MemoryRegionIoeventfd; > =20 > diff --git a/softmmu/memory.c b/softmmu/memory.c > index 7ba2048836..bc0be3f62c 100644 > --- a/softmmu/memory.c > +++ b/softmmu/memory.c > @@ -33,6 +33,7 @@ > #include "qemu/accel.h" > #include "hw/boards.h" > #include "migration/vmstate.h" > +#include "exec/address-spaces.h" > =20 > //#define DEBUG_UNASSIGNED > =20 > @@ -2121,6 +2122,77 @@ void ram_discard_manager_unregister_listener(RamDi= scardManager *rdm, > rdmc->unregister_listener(rdm, rdl); > } > =20 > +/* Called with rcu_read_lock held. */ > +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr, > + ram_addr_t *ram_addr, bool *read_only, > + bool *mr_has_discard_manager) > +{ > + MemoryRegion *mr; > + hwaddr xlat; > + hwaddr len =3D iotlb->addr_mask + 1; > + bool writable =3D iotlb->perm & IOMMU_WO; > + > + if (mr_has_discard_manager) { > + *mr_has_discard_manager =3D false; > + } > + /* > + * The IOMMU TLB entry we have just covers translation through > + * this IOMMU to its immediate target. We need to translate > + * it the rest of the way through to memory. > + */ > + mr =3D address_space_translate(&address_space_memory, iotlb->transla= ted_addr, > + &xlat, &len, writable, MEMTXATTRS_UNSPE= CIFIED); > + if (!memory_region_is_ram(mr)) { > + error_report("iommu map to non memory area %" HWADDR_PRIx "", xl= at); > + return false; > + } else if (memory_region_has_ram_discard_manager(mr)) { > + RamDiscardManager *rdm =3D memory_region_get_ram_discard_manager= (mr); > + MemoryRegionSection tmp =3D { > + .mr =3D mr, > + .offset_within_region =3D xlat, > + .size =3D int128_make64(len), > + }; > + if (mr_has_discard_manager) { > + *mr_has_discard_manager =3D true; > + } > + /* > + * Malicious VMs can map memory into the IOMMU, which is expected > + * to remain discarded. vfio will pin all pages, populating memo= ry. > + * Disallow that. vmstate priorities make sure any RamDiscardMan= ager > + * were already restored before IOMMUs are restored. > + */ > + if (!ram_discard_manager_is_populated(rdm, &tmp)) { > + error_report("iommu map to discarded memory (e.g., unplugged= via" > + " virtio-mem): %" HWADDR_PRIx "", > + iotlb->translated_addr); > + return false; > + } > + } > + > + /* > + * Translation truncates length to the IOMMU page size, > + * check that it did not truncate too much. > + */ > + if (len & iotlb->addr_mask) { > + error_report("iommu has granularity incompatible with target AS"= ); > + return false; > + } > + > + if (vaddr) { > + *vaddr =3D memory_region_get_ram_ptr(mr) + xlat; > + } > + > + if (ram_addr) { > + *ram_addr =3D memory_region_get_ram_addr(mr) + xlat; > + } > + > + if (read_only) { > + *read_only =3D !writable || mr->readonly; > + } > + > + return true; > +} > + > void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client) > { > uint8_t mask =3D 1 << client;