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Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Jason Gunthorpe , Vlastimil Babka Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev References: <20260522-gmem-inplace-conversion-v7-0-2f0fae496530@google.com> <20260522-gmem-inplace-conversion-v7-7-2f0fae496530@google.com> <144bbb9f-39a2-4c90-8903-51521e022da0@arm.com> Content-Language: en-US From: Suzuki K Poulose In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: LO4P123CA0467.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:1aa::22) To PAWPR08MB10975.eurprd08.prod.outlook.com (2603:10a6:102:46e::7) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-TrafficTypeDiagnostic: PAWPR08MB10975:EE_|AM9PR08MB6209:EE_|DU2PEPF00028D0D:EE_|DU0PR08MB8089:EE_ X-MS-Office365-Filtering-Correlation-Id: 2d700268-b808-4759-e3c1-08dec14e78c8 x-checkrecipientrouted: true NoDisclaimer: true X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam-Untrusted: BCL:0;ARA:13230040|366016|376014|7416014|1800799024|18002099003|22082099003|921020|4143699003|11063799006|56012099006; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: L5K9EANu0Jy7D8re3NbJx1LUxUN0Xs33SN7LFRNVMStau4kn4fYYm2LgieMzSvFpK9F7CB9J+bC+ts/sWQ1UTMDTWsGijSbwjhU9EF0275a0JfQENDKrg/96rRuCBrh9Rn6r6lADEmJ99UcgPzqFM4EacvBfuZ0tkSmRiMVmHkRAyGWlfjsHUIblT2vOhiU3NDIGlkd/IjA+P3Ov7Bvq5B52V0k1Te/WIk88f6jclq5/JQ3wpTWns1eIeLltFpP8OZn8ZhL2ovYOX/Dn7WWUSK19d4ubySj/eCRjTTLhV2qYiQr78fqjw7kBjq1K/lq9vjPnfaW9QGC4dPwFYuFVvSU7JBnt4SjSMqp4DGgtbsf8U7Pttf1Rq7N5wE7CqkpR+ZPAy4XRPzl8xiM5zr3ZYAk7aHwBIYMSi4N+/et3mGbgBtco0EO/0CM6fJEmhjvB X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Jun 2026 08:59:51.0535 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2d700268-b808-4759-e3c1-08dec14e78c8 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: DU2PEPF00028D0D.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DU0PR08MB8089 On 02/06/2026 23:41, Ackerley Tng wrote: > Suzuki K Poulose writes: > >> >> [...snip...] >> >>>> @@ -914,7 +916,8 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct >>>> kvm_memory_slot *slot, >>>>           folio_mark_uptodate(folio); >>>>       } >>>> -    r = kvm_gmem_prepare_folio(kvm, slot, gfn, folio); >>>> +    if (kvm_gmem_is_private_mem(inode, index)) >>> >>> Don't we need to make sure the entire folio is private ? Not just the >>> page at the index ? >>>     if (kvm_gmem_range_is_private(, index, folio_nr_pages(folio)) ? > > I was thinking to fix this when I do huge pages, for now guest_memfd is > always just PAGE_SIZE, so just looking up index is fine. > > Is that okay? Thats fine, but would be good to enforce that here, so that we don't miss out when we add support for multi page folios. > >> >> Or rather, we should go through the individual pages and apply the >> prepare for ones that are private ? >> >> Suzuki >> > > IIRC the plan was to make kvm_gmem_prepare_folio() idempotent, as in, if > a page is already private, just skip. Currently sev_gmem_prepare() does > a pr_debug(), which I guess is technically still idempotent. > > I'm thinking that the information tha needs tracking to make > .gmem_prepare() idempotent should be tracked by arch code. > > Does this work for ARM CCA? We don't hook into the prepare yet, but have plans to do that. We should be able to handle the pages that are already private. (For CCA context, RMI_GRANULE_DELEGATE_RANGE can skip over already REALM pages). So this should be fine. My point is, in a given folio, there may be pages that are shared. Like you said, this could be dealt with when we support hugepages. Suzuki > >>> >>> [...snip...] >>>