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Introduction of runqueue per cpupool for credit2 scheduler – Xen

Current infrastructure in Xen allows only a global runqueue flags that will be applicable to all the cpupools (schedulers, there is 1:1 correspondence between cpupools and scheduler instance running in a system). for eg. if we have selected configuration of runqueue as socket, then all the cpupools created will have the runqueue per cpupool. This […]

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Random host crash when running Xen + Braindump pvMMU.

Kernel crash call trace Apr 6 02:50:06 localhost kernel: [ 3107.388117] [] dump_stack+0x19/0x20 Apr 6 02:50:06 localhost kernel: [ 3107.388119] [] warn_slowpath_common+0x70/0xa0 Apr 6 02:50:06 localhost kernel: [ 3107.388122] [] warn_slowpath_null+0x1a/0x20 Apr 6 02:50:06 localhost kernel: [ 3107.388125] [] xen_mc_flush+0x177/0x190 Apr 6 02:50:06 localhost kernel: [ 3107.388128] [] __xen_pgd_pin+0x23c/0x290 Apr 6 02:50:06 localhost kernel: [ […]

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GPU Passthrough under ballooning + XEN and role of POD driver.

Its happening only in case HVM guest. I used Win 7 64 bit of reproducing the crash. This article is in continuation with the previous one where I saw a crash in RMRR region in case of GPU passthrough. To work around this problem I introduced a memory whole of 2 GB in the guest […]

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RMRR region GPU passthough + xen

Today faced with a issue where one VM is assigned GPU via passthrough mode and other VM doesn’t have GPU assignement. If I swap the max and min dynamic memory assignment of both these VMs (changing the size of balloon for each VM), guest with GPU crashes after 2-3 iterations. E820 Map of Host: (XEN) […]

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multipage support for netback driver + Xen

Here are some of my learnings from my work on multipage support for netback driver. Learnings related to how we are making use of multi page and also how netback and netfron communicate. driver/xen/xen_probe.c keeps monitoring the backend and frontend states and calls the appropriate driver.otherend_changed(drivers/net/netfront or driver/net/netback) function. xenbus.c : static DEFINE_XENBUS_DRIVER(netback, , .probe […]

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Broadwell + Xen + Classic guest kernel + WRITE_FAULT + SMAP Violation.

Recently faced an issue where classic guest kernel (2.6.*) were faulting on Broadwell hardware. From the day 1 doubt was on SMAP feature that is exclusive to Broadwell but had to prove it. Approach: Compiled the guest kernel with instrumentation but can’t use it as the guest on Broadwell hangs just during reboot. (I compiled […]

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Xen brief – Architecture

Xen architcture dom0 dom1 dom2 (guest OS) (guest OS) (guest OS) —————-Xen Hypervisor————————- ——————-Hw Resources———————— dom0 priviledged – ring 0 , mostly linux dom1 , dom2 … domN – unpriviledged ring 3 Role of dom0: This is the first guest to run when Xen starts Handling devices, including multiplexing of them for VMs Implementing half […]

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