Virtual machine migration in rack scale systems

A destination shared memory controller (SMC), comprising:

• a direct memory access (DMA) move engine to:
• establish a first virtual channel (VC) over a link with a source SMC coupled to a source node that hosted a virtual machine (VM) that migrated to a second node coupled to the destination SMC, the link to support both memory semantics and an input/output (I/O) protocol;
• request, via the first VC, units of data corresponding to the VM from the source SMC;
• and
• receive, via the first VC from the source SMC, the units of data and directory state metadata associated with each received unit of data;
• a demand request component to:
• establish a second VC over the link with the source SMC, the second VC separate from the first VC;
• receive a demand request for one of the units of data corresponding to the VM;
• determine that the requested unit of data has not been transferred to the destination SMC;
• transmit, via the second VC, the demand request to the source SMC;
• and
• receive, via the second VC from the source SMC, the requested unit of data and corresponding directory state metadata for the requested unit of data.

A method comprising:

• establishing, by a destination shared memory controller (SMC), a first virtual channel (VC) over a link with a source SMC, the source SMC coupled to a source node that hosted a virtual machine (VM) that migrated to a destination node coupled to the destination SMC, and wherein the link to support both memory semantics and an input/output (I/O) protocol;
• receiving, via the first VC from the source SMC, units of data corresponding to the VM and directory state metadata associated with each unit of data;
• establishing, by the destination SMC, a second VC over the link with the source SMC, the second VC separate from the first VC;
• receiving, by the destination SMC, a demand request for one of the units of data corresponding to the VM;
• determining, by the destination SMC, that the unit of data has not been transferred to the destination SMC;
• responsive to determining that the unit of data has not be transferred, forwarding, via the second VC, the demand request to the source SMC;
• and
• receiving, via the second VC from the source SMC, a response to the demand request, the response comprising the requested unit of data and corresponding directory state metadata for the requested unit of data.

A method comprising:

• establishing, by a source shared memory controller (SMC), a first virtual channel (VC) over a link with a destination SMC, the destination SMC coupled to a destination node hosting a virtual machine (VM), wherein the VM is migrated to the destination node from a source node coupled to the source SMC, and wherein the link to support both memory semantics and an input/output (I/O) protocol;
• receiving, by the source SMC via the first VC to the source SMC, a request for units of data corresponding to the VM and directory state metadata associated with each unit of data;
• responsive to the request for the units of data, sending, by the source SMC via the first VC, the units of data and the directory state metadata associated with each unit of data;
• establishing, by the source SMC, a second VC over the link with the destination SMC, the second VC separate from the first VC;
• receiving, by the source SMC, a demand request for one of the units of data corresponding to the VM from the destination SMC;
• and
• transmitting, via the second VC, the requested unit of data and corresponding directory state metadata for the requested unit of data to the destination SMC.