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Linux Kernel

braindump- memory corruption

Linux kernel 3.10 has somewhat dubious use of __GFP_WAIT which is more recent kernel has been replaced __GFP_RECLAIM and __GFP_DIRECT_RECLAIM which are more sensible . I have been debugging a customer issue where AMD GPU passhtrough for S9050 card is causing XenServer host running 3.10 kernel to crash but XenServer 7.x Tech Preview release with […]

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Braindump + Segmentation and Paging And Xen

32 bit PV guest: guest kernel executes in ring 1 and guest user space executes in ring3. 64 bit PV guest: Guest kernel executes in ring 3 and guest user space also executes in ring 3. In 32 bit PV guest Xen used to use Segmentation based protection to protect Xen memory from being accessed […]

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Interrupt Path on Xen and on Baremetal system.

I was exploring an issue where qlogic device interrupt vector corresponding to a particular TX ring remained in masked state after the device comes up or is resetted. So the no packet transfer was possible on a port which was using that Tx queue and due to inaction, after some time this ports used to […]

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Kernel Protocol Stack

IP Processing: The IP protocol receive function ip_recv() is called when an IP packet is dequeued. It verifies packet integrity and invokes any netfilter hooks, then calls ip_rcv_finish(), which routes the packet over the network or delivers it locally by ip_local_deliver(). There, the highter layer protocol is determined and the corresponding handler function is invoked.: […]

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Notification chain – linux kernel

Notifier chains send status change messages to code regions that request them. Unlike hard-coded mechanisms, notifiers offer a versatile technique for dynamically loadable code to get notified when events of interest occur. Notifier chains were originally added to pass network events to concerned sections of the kernel, but are now used for many other purposes. […]

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