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Thu, 18 Dec 2025 14:24:22 +0000 (UTC) X-Farcaster-Flow-ID: b8e9a253-10d9-4617-9a75-3cd1f6a0b577 Received: from EX19D012EUA001.ant.amazon.com (10.252.50.122) by EX19MTAEUA002.ant.amazon.com (10.252.50.124) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.29; Thu, 18 Dec 2025 14:24:21 +0000 Received: from EX19D012EUA001.ant.amazon.com (10.252.50.122) by EX19D012EUA001.ant.amazon.com (10.252.50.122) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Thu, 18 Dec 2025 14:24:21 +0000 Received: from EX19D012EUA001.ant.amazon.com ([fe80::b7ea:84f7:2c4b:2719]) by EX19D012EUA001.ant.amazon.com ([fe80::b7ea:84f7:2c4b:2719%3]) with mapi id 15.02.2562.035; Thu, 18 Dec 2025 14:24:21 +0000 From: "Chalios, Babis" To: "robh@kernel.org" , "krzk+dt@kernel.org" , "conor+dt@kernel.org" , "richardcochran@gmail.com" , "dwmw2@infradead.org" , "andrew+netdev@lunn.ch" , "davem@davemloft.net" , "edumazet@google.com" , "kuba@kernel.org" , "pabeni@redhat.com" CC: "devicetree@vger.kernel.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Chalios, Babis" , "Graf (AWS), Alexander" , "mzxreary@0pointer.de" , "Cali, Marco" , "Woodhouse, David" Subject: [PATCH v4 1/7] ptp: vmclock: add vm generation counter Thread-Topic: [PATCH v4 1/7] ptp: vmclock: add vm generation counter Thread-Index: AQHccCoA8Zlu7ja/r0auHBzyScVYrg== Date: Thu, 18 Dec 2025 14:24:21 +0000 Message-ID: <20251218142408.8395-2-bchalios@amazon.es> References: <20251218142408.8395-1-bchalios@amazon.es> In-Reply-To: <20251218142408.8395-1-bchalios@amazon.es> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Similar to live migration, loading a VM from some saved state (aka=0A= snapshot) is also an event that calls for clock adjustments in the=0A= guest. However, guests might want to take more actions as a response to=0A= such events, e.g. as discarding UUIDs, resetting network connections,=0A= reseeding entropy pools, etc. These are actions that guests don't=0A= typically take during live migration, so add a new field in the=0A= vmclock_abi called vm_generation_counter which informs the guest about=0A= such events.=0A= =0A= Hypervisor advertises support for vm_generation_counter through the=0A= VMCLOCK_FLAG_VM_GEN_COUNTER_PRESENT flag. Users need to check the=0A= presence of this bit in vmclock_abi flags field before using this flag.=0A= =0A= Signed-off-by: Babis Chalios =0A= Reviewed-by: David Woodhouse =0A= ---=0A= include/uapi/linux/vmclock-abi.h | 15 +++++++++++++++=0A= 1 file changed, 15 insertions(+)=0A= =0A= diff --git a/include/uapi/linux/vmclock-abi.h b/include/uapi/linux/vmclock-= abi.h=0A= index 2d99b29ac44a..937fe00e4f33 100644=0A= --- a/include/uapi/linux/vmclock-abi.h=0A= +++ b/include/uapi/linux/vmclock-abi.h=0A= @@ -115,6 +115,12 @@ struct vmclock_abi {=0A= * bit again after the update, using the about-to-be-valid fields.=0A= */=0A= #define VMCLOCK_FLAG_TIME_MONOTONIC (1 << 7)=0A= + /*=0A= + * If the VM_GEN_COUNTER_PRESENT flag is set, the hypervisor will=0A= + * bump the vm_generation_counter field every time the guest is=0A= + * loaded from some save state (restored from a snapshot).=0A= + */=0A= +#define VMCLOCK_FLAG_VM_GEN_COUNTER_PRESENT (1 << 8)=0A= =0A= __u8 pad[2];=0A= __u8 clock_status;=0A= @@ -177,6 +183,15 @@ struct vmclock_abi {=0A= __le64 time_frac_sec; /* Units of 1/2^64 of a second */=0A= __le64 time_esterror_nanosec;=0A= __le64 time_maxerror_nanosec;=0A= +=0A= + /*=0A= + * This field changes to another non-repeating value when the guest=0A= + * has been loaded from a snapshot. In addition to handling a=0A= + * disruption in time (which will also be signalled through the=0A= + * disruption_marker field), a guest may wish to discard UUIDs,=0A= + * reset network connections, reseed entropy, etc.=0A= + */=0A= + __le64 vm_generation_counter;=0A= };=0A= =0A= #endif /* __VMCLOCK_ABI_H__ */=0A= -- =0A= 2.34.1=0A= =0A=