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 D6oKG6SZ 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 12/1/25 12:25 PM, David Hildenbrand (Red Hat) wrote: > On 12/1/25 18:15, Pratik R. Sampat wrote: >> Hi David, >> >> On 11/28/25 3:34 AM, David Hildenbrand (Red Hat) wrote: >>> On 11/27/25 18:40, Kiryl Shutsemau wrote: >>>> On Wed, Nov 26, 2025 at 04:27:29PM -0600, Pratik R. Sampat wrote: >>>>> >>>>> >>>>> On 11/26/25 5:12 AM, Kiryl Shutsemau wrote: >>>>>> On Tue, Nov 25, 2025 at 11:57:51AM -0600, Pratik R. Sampat wrote: >>>>>>> The unaccepted memory structure currently only supports accepting memory >>>>>>> present at boot time. The unaccepted table uses a fixed-size bitmap >>>>>>> reserved in memblock based on the initial memory layout, preventing >>>>>>> dynamic addition of memory ranges after boot. This causes guest >>>>>>> termination when memory is hot-added in a secure virtual machine due to >>>>>>> accessing pages that have not transitioned to private before use. >>>>>> >>>>>> How does the hot-pluggable memory look in EFI memory map? I thought >>>>>> hot-pluggable ranges suppose to be declared thare. The cleanest solution >>>>>> would be to have hot-pluggable and unaccepted indicated in EFI memory, >>>>>> so we can size bitmap accordingly upfront. >>>>>> >>>>> >>>>> I'm not quite sure if I fully understand. Do you mean to refer to the >>>>> EFI_MEMORY_HOT_PLUGGABLE attribute that is used for cold plugged boot >>>>> memory? If so, wouldn't it still be desirable to increase the size of >>>>> the bitmap to what was marked as hotpluggable initially? >>>> >>>> I just don't understand how hotpluggable memory presented in EFI memory >>>> map in presence of unaccepted memory. If not-yet-plugged memory marked >>>> as unaccepted we can preallocate bitmap upfront and make unaccepted >>>> memory transparent wrt hotplug. >>>> >>>> BTW, isn't virtio-mem a more attractive target to support than HW-style >>>> hotplug? >>> >>> I would have thought so as well, such that we can just let virtio-mem take care of any acceptance before actually using hotplugged memory (exposing it to the buddy). >>> >>> Likely there is desire to support other hypervisors? >> >> That's true. We are certainly thinking about how the RAM discard manager >> should look like with multiple states to allow guest_memfd and >> virtio-mem to work together. >> > > Right, there is the QEMU side of it as well. > >> Since both paths in Linux eventually converge around >> add_memory_resource(), based on some light hacking in QEMU I could see >> similar hotplug behavior for virtio-mem as well. > > For virtio-mem it would not be add_memory_resource(). > > Whenever we would be plugging memory we would be accepting it, and when we would be unplugging memory we would unaccept it. > > That is, acceptance does not happen at add_memory_resource() time, but when virtio-mem asks the device to transition a device block from unplugged<->plugged. Ah, I see. Thanks for clearing that up!