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Thu, 27 Oct 2022 19:23:31 -0700 (PDT) MIME-Version: 1.0 References: <20221027074032.1101939-1-lulu@redhat.com> <20221027074032.1101939-2-lulu@redhat.com> <20221027151134.354bd3bb.alex.williamson@redhat.com> <20221027200811.7e586f7b.alex.williamson@redhat.com> In-Reply-To: <20221027200811.7e586f7b.alex.williamson@redhat.com> From: Jason Wang Date: Fri, 28 Oct 2022 10:23:16 +0800 Message-ID: Subject: Re: [PATCH v4 1/2] vfio: move the function vfio_get_xlat_addr() to memory.c To: Alex Williamson Cc: Cindy Lu , mst@redhat.com, pbonzini@redhat.com, peterx@redhat.com, david@redhat.com, f4bug@amsat.org, sgarzare@redhat.com, qemu-devel@nongnu.org Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=170.10.133.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.515, 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 Fri, Oct 28, 2022 at 10:08 AM Alex Williamson wrote: > > On Fri, 28 Oct 2022 09:50:10 +0800 > Jason Wang wrote: > > > On Fri, Oct 28, 2022 at 5:11 AM Alex Williamson > > wrote: > > > > > > On Thu, 27 Oct 2022 15:40:31 +0800 > > > Cindy Lu wrote: > > > > > > > Move the function vfio_get_xlat_addr to softmmu/memory.c, and > > > > change the name to memory_get_xlat_addr().So we can use this > > > > function in other devices,such as vDPA device. > > > > > > > > Signed-off-by: Cindy Lu > > > > --- > > > > hw/vfio/common.c | 92 ++----------------------------------------- > > > > include/exec/memory.h | 4 ++ > > > > softmmu/memory.c | 84 +++++++++++++++++++++++++++++++++++++++ > > > > 3 files changed, 92 insertions(+), 88 deletions(-) > > > > > > > > diff --git a/hw/vfio/common.c b/hw/vfio/common.c > > > > index ace9562a9b..2b5a9f3d8d 100644 > > > > --- a/hw/vfio/common.c > > > > +++ b/hw/vfio/common.c > > > > @@ -574,92 +574,6 @@ static bool vfio_listener_skipped_section(MemoryRegionSection *section) > > > > section->offset_within_address_space & (1ULL << 63); > > > > } > > > > > > > > -/* Called with rcu_read_lock held. */ > > > > -static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr, > > > > - ram_addr_t *ram_addr, bool *read_only) > > > > -{ > > > > - MemoryRegion *mr; > > > > - hwaddr xlat; > > > > - hwaddr len = iotlb->addr_mask + 1; > > > > - bool writable = 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 = 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 = memory_region_get_ram_discard_manager(mr); > > > > - MemoryRegionSection tmp = { > > > > - .mr = mr, > > > > - .offset_within_region = xlat, > > > > - .size = int128_make64(len), > > > > - }; > > > > - > > > > - /* > > > > - * Malicious VMs can map memory into the IOMMU, which is expected > > > > - * to remain discarded. vfio will pin all pages, populating memory. > > > > - * Disallow that. vmstate priorities make sure any RamDiscardManager > > > > - * 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; > > > > - } > > > > - > > > > - /* > > > > - * Malicious VMs might trigger discarding of IOMMU-mapped memory. The > > > > - * pages will remain pinned inside vfio until unmapped, resulting in a > > > > - * higher memory consumption than expected. If memory would get > > > > - * populated again later, there would be an inconsistency between 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 never be > > > > - * exceeded and can be used to mitigate this problem. > > > > - */ > > > > - 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."); > > > > - } > > > > - > > > > - /* > > > > - * 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 = memory_region_get_ram_ptr(mr) + xlat; > > > > - } > > > > - > > > > - if (ram_addr) { > > > > - *ram_addr = memory_region_get_ram_addr(mr) + xlat; > > > > - } > > > > - > > > > - if (read_only) { > > > > - *read_only = !writable || mr->readonly; > > > > - } > > > > - > > > > - return true; > > > > -} > > > > - > > > > static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb) > > > > { > > > > VFIOGuestIOMMU *giommu = container_of(n, VFIOGuestIOMMU, n); > > > > @@ -682,7 +596,8 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb) > > > > if ((iotlb->perm & IOMMU_RW) != IOMMU_NONE) { > > > > bool read_only; > > > > > > > > - if (!vfio_get_xlat_addr(iotlb, &vaddr, NULL, &read_only)) { > > > > + if (!memory_get_xlat_addr(iotlb, &vaddr, NULL, &read_only, > > > > + &address_space_memory)) { > > > > goto out; > > > > } > > > > /* > > > > @@ -1359,7 +1274,8 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb) > > > > } > > > > > > > > rcu_read_lock(); > > > > - if (vfio_get_xlat_addr(iotlb, NULL, &translated_addr, NULL)) { > > > > + if (memory_get_xlat_addr(iotlb, NULL, &translated_addr, NULL, > > > > + &address_space_memory)) { > > > > int ret; > > > > > > > > ret = vfio_get_dirty_bitmap(container, iova, iotlb->addr_mask + 1, > > > > diff --git a/include/exec/memory.h b/include/exec/memory.h > > > > index bfb1de8eea..282de1d5ad 100644 > > > > --- a/include/exec/memory.h > > > > +++ b/include/exec/memory.h > > > > @@ -713,6 +713,10 @@ void ram_discard_manager_register_listener(RamDiscardManager *rdm, > > > > void ram_discard_manager_unregister_listener(RamDiscardManager *rdm, > > > > RamDiscardListener *rdl); > > > > > > > > +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr, > > > > + ram_addr_t *ram_addr, bool *read_only, > > > > + AddressSpace *as); > > > > + > > > > typedef struct CoalescedMemoryRange CoalescedMemoryRange; > > > > typedef struct MemoryRegionIoeventfd MemoryRegionIoeventfd; > > > > > > > > diff --git a/softmmu/memory.c b/softmmu/memory.c > > > > index 7ba2048836..8586863ffa 100644 > > > > --- a/softmmu/memory.c > > > > +++ b/softmmu/memory.c > > > > @@ -2121,6 +2121,90 @@ void ram_discard_manager_unregister_listener(RamDiscardManager *rdm, > > > > rdmc->unregister_listener(rdm, rdl); > > > > } > > > > > > > > +/* Called with rcu_read_lock held. */ > > > > +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr, > > > > + ram_addr_t *ram_addr, bool *read_only, > > > > + AddressSpace *as) > > > > +{ > > > > + MemoryRegion *mr; > > > > + hwaddr xlat; > > > > + hwaddr len = iotlb->addr_mask + 1; > > > > + bool writable = 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 = address_space_translate(as, 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 = memory_region_get_ram_discard_manager(mr); > > > > + MemoryRegionSection tmp = { > > > > + .mr = mr, > > > > + .offset_within_region = xlat, > > > > + .size = int128_make64(len), > > > > + }; > > > > + > > > > + /* > > > > + * Malicious VMs can map memory into the IOMMU, which is expected > > > > + * to remain discarded. device will pin all pages, populating memory. > > > > + * Disallow that. vmstate priorities make sure any RamDiscardManager > > > > + * 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; > > > > + } > > > > + > > > > + /* > > > > + * Malicious VMs might trigger discarding of IOMMU-mapped memory. The > > > > + * pages will remain pinned inside device until unmapped, resulting in a > > > > + * higher memory consumption than expected. If memory would get > > > > + * populated again later, there would be an inconsistency between pages > > > > + * pinned by device 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 never be > > > > + * exceeded and can be used to mitigate this problem. > > > > + */ > > > > + warn_report_once("Using device 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."); > > > > > > Is this really fit to be in shared code? Simply replacing "vfio" with > > > "device" for comments and warnings that are really of concern for a > > > specific use case doesn't look much better to me. > > > > > > I think translating an unpopulated address, as in the previous test > > > above, is generally invalid, but the comment is certainly trying to > > > frame the severity of this error relative to a specific use case. > > > > > > Here we're generating an unconditional warning, assuming that this code > > > path has been triggered by device code, for the condition of simply > > > asking for a translation to a MemoryRegion under discard manager > > > control? Again, isn't that an action that has implications for a > > > specific use case of a device that supports pinning host memory? > > > > > > Or can we rename the function to memory_get_xlat_addr_no_discard()? > > This looks more general and fit for the caller that doesn't want to > > map region that has a discard manager. > > Is a guest restricted from mapping virtio-mem regions to a device? For the region that is not populated, it should be restricted. If this is wrong, we need a separate fix. > AFAIK, this is something that a guest can do and we can't restrict them > from doing it, it's just that it opens some potential for malicious > activity that we rely on things like locked memory limits to keep from > getting out of hand. Thanks, So it's the fault of the name, it could be memory_get_xlat_addr_no_unpopulated_discard(). Or as I replied, stick to what you've suggested. Thanks > > Alex > > > > Should the shared code be generating this warning, or could an optional > > > pointer arg be updated to indicate a translation to discard manager > > > controlled memory and this comment and warning should remain in the > > > caller? Thanks, > > > > I think this should also work. > > > > Thanks > > > > > > > > Alex > > > > > > > + } > > > > + > > > > + /* > > > > + * 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 = memory_region_get_ram_ptr(mr) + xlat; > > > > + } > > > > + > > > > + if (ram_addr) { > > > > + *ram_addr = memory_region_get_ram_addr(mr) + xlat; > > > > + } > > > > + > > > > + if (read_only) { > > > > + *read_only = !writable || mr->readonly; > > > > + } > > > > + > > > > + return true; > > > > +} > > > > + > > > > void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client) > > > > { > > > > uint8_t mask = 1 << client; > > > > > >