[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH v3 1/2] x86/mm: rename FLUSH_FORCE_IPI to FLUSH_NO_ASSIST
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
- Date: Wed, 25 May 2022 14:33:01 +0000
- Accept-language: en-GB, en-US
- Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none
- Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=AOo5nijY1u8TBtG0yW8aJXoOG2wZlRWmGERCTzrYVec=; b=GNg6oz3DJSxxqM9gMhoolCYlPMxAiKsHXd9P9VPAen4vA+vuJPcVQBjHCoO0PF4QrCM/ZwHjmM8s0VmpxQ9rTfak6qQ4V+KzIJ1ym9Vqw/8d+7mDqI/FwZ7KroX61QE0K44PVk8usV+CejueqTqce9dqG1TIAj1PB63VDHVe7esmbIlxjy7uPua/eWRnf8WNw5eJJ3fF/Fa3MFpP2G4XGF75efye76XSubeSqc5FIv19Kec0NkxjVoJWn9rcBZZ7ebbUDOv908nZnI7tpVtKaKp+1tBlMS5EaaHsTciF6g2pY5HNC6nYWCzXIgUv42BS+3aEcNlxoc5uTbL0rc1J8A==
- Arc-seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Wbp6pdtb3k6bCtop+bDTBZfXzn0vpoCHT//GmvNO1Jlmj42CkoEd1eJEKFCC2Ek75RYYGqMQ5PYRSzai4KZRqlGD77YJglY6btrrbUgvbG3hnudOdwwz8+DZ9LV1yBxxo1ZbanZv0nWJzOR+m/SGN/doSLe0QuvbxpcWSPAB4RW3OfS5s3leIzdEeDQJOeGPcjN2GGSNrTtksGtnnsTk+13/qyb7DQNTZMW5WmHtQrHDs6eTyKnCzHhdtr5RbMYqRL4M7TXLqM5FI7z6GIXDDH8GMpv3j27iv5Hs8PLRLNqr2u4mm2c6qfa4IDPU1GsD4qy3iq+9U//tJ13zbmXv6w==
- Authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com;
- Cc: Wei Liu <wl@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>
- Delivery-date: Wed, 25 May 2022 14:33:26 +0000
- Ironport-data: A9a23:Ul2OxqvdWUshDPN6/PCy4iGeROfnVCZfMUV32f8akzHdYApBsoF/q tZmKT3TM66JMzf3e98lPt+0oBwBvJODyIUwGVFoqi5kRS0a+JbJXdiXEBz9bniYRiHhoOOLz Cm8hv3odp1coqr0/0/1WlTZhSAgk/nOHNIQMcacUsxLbVYMpBwJ1FQywobVvqYy2YLjW17X5 IuryyHiEATNNwBcYzp8B52r8HuDjNyq0N/PlgVjDRzjlAa2e0g9VPrzF4noR5fLatA88tqBb /TC1NmEElbxpH/BPD8HfoHTKSXmSpaKVeSHZ+E/t6KK2nCurQRquko32WZ1he66RFxlkvgoo Oihu6BcRi8pMZPWpcMyCyV9MH5UJYF20rvfEUWW5Jn7I03uKxMAwt1IJWRuYcg037gyBmtDs /sFNDoKcxaPwfqsx662QfVtgcJlK9T3OIQYuTdryjSx4fQOGMifBfmVo4ADmmtr7ixNNa+2i 84xQDxjdhnfJTZIPU8aEskWl+a0nHjvNTZfrTp5oIJovzaMk1cvgNABNvL4Q8C3dcF0xH/F+ G6bxXzrXiMmBuCQnG/tHnWEw7WncTnAcIAYGaC89/VqqEaO3WFVAxoTPXOkpdGph0j4XMhQQ 2QE9yxroaUs+UiDStjmQwb+sHOCpgQbWddbD6s98g7l90bPywOQB2xBQjsfbtUj7J8yXWZyi gTPmM71DztytrHTUWia6rqfsTK1P24SMHMGYigHCwAC5rEPvb0Os/4Gdf47eIbdszE/MWuYL +yixMTmu4gusA==
- Ironport-hdrordr: A9a23:POXz9quBj7srALf0VZiYYe8e7skCL4Aji2hC6mlwRA09TyXGra 2TdaUgvyMc1gx7ZJh5o6H6BEGBKUmslqKceeEqTPuftXrdyRGVxeZZnMTfKlzbamDDH4tmuZ uIHJIOb+EYYWIasS++2njBLz9C+qjIzEnLv5a5854Fd2gDBM9dBkVCe3+m+yZNNWt77O8CZf 6hD7181l+dkBosDviTNz0gZazuttfLnJXpbVotHBg88jSDijuu9frTDwWY9g12aUIO/Z4StU z+1yDp7KSqtP+2jjXG0XXI0phQkNz9jvNeGc23jNQPIDmEsHfqWG0hYczBgNkGmpDq1L8Yqq iKn/7mBbU015rlRBDxnfIq4Xi47N9h0Q679bbSuwqfnSWwfkNHNyMGv/MZTvKR0TtfgDk3up g7oF6xpt5ZCwjNkz/64MWNXxZ2llCsqX5niuILiWdDOLFuIIO5gLZvin+9Kq1wVR4SKbpXYt VGHYXZ/rJbYFmaZ3fWsi1mx8GtRG06GlODTlIZssKY3jBKlDQhpnFojvA3jzMF7tYwWpNE7+ PLPuBhk6xPVNYfaeZ4CP0aScW6B2TRSVbHMX6UI17gCKYbUki94KLf8fEw/qWnaZYIxJw9lN DIV05Zr3c7fwb0BciHzPRwg2fwqaWGLEDQI+1lluhEU+fHNcvW2AW4OSMTutrlpekDCcvGXP v2MI5KApbYXB7TJbo=
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHYcA9OnQ9W6lKd/EmmrY4D8odolq0vawYAgAAGBACAADeDgA==
- Thread-topic: [PATCH v3 1/2] x86/mm: rename FLUSH_FORCE_IPI to FLUSH_NO_ASSIST
On 25/05/2022 12:14, Jan Beulich wrote:
> On 25.05.2022 12:52, Andrew Cooper wrote:
>> On 25/05/2022 09:13, Roger Pau Monne wrote:
>>> Rename the flag to better note that it's not actually forcing any IPIs
>>> to be issued if none is required, but merely avoiding the usage of TLB
>>> flush assistance (which itself can avoid the sending of IPIs to remote
>>> processors).
>>>
>>> No functional change expected.
>>>
>>> Requested-by: Jan Beulich <jbeulich@xxxxxxxx>
>>> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>>> ---
>>> Changes since v2:
>>> - New in this version.
>> :( This needs reverting.
>>
>> It is specific to IPIs, because of our current choice of algorithm for
>> freeing pagetables.
>>
>> "no assist" excludes ipi-helper hypercalls which invoke
>> INVALIDATE_TLB_VECTOR. Such hypercalls do exist and specifically would
>> be improvement that we ought to use.
>>
>> Furthermore, we do want to work around the limitation that created
>> FLUSH_FORCE_IPI, because we absolutely do want to be able to use
>> hypercalls/remote TLB flushing capabilities when available.
>>
>> I accept that FORCE_IPI perhaps isn't a perfect name, but it's a whole
>> lot less bad than NO_ASSIST.
> But FORCE_IPI has caused actual confusion while reviewing patch 2.
> If NO_ASSIST doesn't suit you and FORCE_IPI is also wrong, can you
> suggest a better name fitting both aspects?
I don't actually agree that FORCE_IPI is unclear to begin with.
The safety property required is "if you need to contact a remote CPU, it
must be by IPI to interlock with Xen's #PF handler".
FORCE_IPI is very close to meaning this. If anything else is unclear,
it can be clarified in the adjacent comment.
~Andrew
|
