From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 643F92D3EE5; Fri, 27 Mar 2026 08:49:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774601381; cv=none; b=YhUQnclPqRqOoIoE97QgLvz31Etfg20fKXvsOARtkP8MrZH+MgX/zqGVXu0omur00Tqt6cJyZthFKuCz6IqMaIIBn3jPu3w9H2O8ppLMiLJ68h2jy9DGI1VA26aaUuBb9CICfIfqSBYPtbmnArsEFN2nqMnqEHOQvix0TOqszzg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774601381; c=relaxed/simple; bh=Pexv9TpMbhzUb/4Dk8B82YA2sdAT+FiSMIun6H7kW3M=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NuV+c+T60GOxo1th/Q7tyjXJb3t/iuxlxBtdiZ3ho5S5bTS4Ik6CSeA53JqjA/1O5zcAPZUzp/Z8E+4Hcrap4/H0GaVMpTQ0i0XobQ1Z6FDww22PRlmPcNtnmzTNKy0zZd57XB79iS/WhfzjOGRznWWxNUL6zv77A4xK1TmP1FY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UjGNBzZK; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UjGNBzZK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 14DCCC19423; Fri, 27 Mar 2026 08:49:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774601381; bh=Pexv9TpMbhzUb/4Dk8B82YA2sdAT+FiSMIun6H7kW3M=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=UjGNBzZKc8pCzxavJ9tJ+qwMtEXA6nzq4zQm/hsKDVydmYNrqgZyW/qnA2LtqWFh4 fj5MJTlAaICQvGehIbTvkRzCByLHHF2pcNkbvBbvGVkJYLTstQE0395OibDT1At0rq JgGb28C2+oNzHG6xcc5WX2P5pThVVS9jmIjZi+LwHD8PkDy4qcbu6N7QufD1GgQVkL XxcyUwk9o6bIQsZleDgPgGM1FD3sbH2yfbJGaQE61vGOR84hdSFRcP0553LqzUgUVK W9BpMKSERM3T7WWhn3TClEbpagXkS2EG8yC5QzGIYPsDwQxCvQL4VaSOGeo0SLYkVh nWUM4ITvfQMbQ== Message-ID: <5bfbe0e4-41ad-4752-bd6f-6eb1b7c84215@kernel.org> Date: Fri, 27 Mar 2026 09:49:34 +0100 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] x86/tdx: Accept hotplugged memory before online To: Chenyi Qiang , =?UTF-8?Q?Marc-Andr=C3=A9_Lureau?= , "Edgecombe, Rick P" Cc: "bp@alien8.de" , "kas@kernel.org" , "hpa@zytor.com" , "mingo@redhat.com" , "x86@kernel.org" , "tglx@kernel.org" , "dave.hansen@linux.intel.com" , "kvm@vger.kernel.org" , "linux-coco@lists.linux.dev" , "linux-kernel@vger.kernel.org" , "Bonzini, Paolo" References: <20260324-tdx-hotplug-fixes-v1-0-8f29f2c17278@redhat.com> <20260324-tdx-hotplug-fixes-v1-2-8f29f2c17278@redhat.com> <56190adc345148396ba6b3e52672e662145f7dc7.camel@intel.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 3/27/26 04:05, Chenyi Qiang wrote: > > > On 3/25/2026 6:29 PM, Marc-André Lureau wrote: >> Hi >> >> On Wed, Mar 25, 2026 at 2:04 AM Edgecombe, Rick P >> wrote: >>> >>> >>> Does this depend on patch 1 somehow? >> >> Yes, if I plug, unplug and plug again I get this without PATCH 1: >> [root@rhel10-server ~]# [ 5707.392231] virtio_mem virtio5: plugged >> size: 0x80000000 >> [ 5707.395583] virtio_mem virtio5: requested size: 0x0 >> >> [root@rhel10-server ~]# [ 5714.648501] virtio_mem virtio5: plugged >> size: 0x2e00000 >> [ 5714.651808] virtio_mem virtio5: requested size: 0x80000000 >> [ 5714.676296] tdx: Failed to accept memory [0x108000000, 0x110000000) >> [ 5714.683980] tdx: Failed to accept memory [0x110000000, 0x118000000) >> [ 5714.686997] tdx: Failed to accept memory [0x140000000, 0x148000000) >> [ 5714.689989] tdx: Failed to accept memory [0x128000000, 0x130000000) >> [ 5714.694981] tdx: Failed to accept memory [0x148000000, 0x150000000) >> [ 5714.704064] tdx: Failed to accept memory [0x138000000, 0x140000000) >> [ 5714.710144] tdx: Failed to accept memory [0x118000000, 0x120000000) >> [ 5714.722532] tdx: Failed to accept memory [0x130000000, 0x138000000) >> >> My understanding is that QEMU should eventually unplug the memory and >> PUNCH_HOLE then KVM should TDH.MEM.PAGE.REMOVE, but that doesn't seem >> to happen. > > I guess it doesn't happen because virtio-mem in QEMU only PUNCH_HOLE the > shared memory by ram_block_discard_range() but it doesn't touch the private > memory which should be discarded by ram_block_discard_guest_memfd_range(). > > Is this strictly required? According to the specification, So far nobody specified how virtio-mem should behave in a CoCo environment. I assume that we need enhancements on the driver and the device side. In Linux, we should not be accepting memory during memory onlining/offlining through notifiers, as we might only hot(un)plug parts of a memory block etc. We need some explicit calls into the core before we hand hotplugged memory to the core, and before we hand back unplugged memory to the device. In QEMU, I would similarly assume that we might have to perform some additional work when converting memory blocks. *maybe* that would just be done by the guest that converts memory from private to shared before unplug etc. -- Cheers, David