29 lines
1013 B
Plaintext
29 lines
1013 B
Plaintext
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From: jbeulich@novell.com
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Subject: Xen: improve floppy behavior
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Patch-mainline: n/a
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References: bnc#584216
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Timing is significantly different from native both because Xen traps
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I/O port accesses and using DMA not being possible (without intrusive
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changes). Due to the overhead of trapped port accesses, I/O is already
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slow enough (and Xen doesn't run on very old hardware anyway), so the
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situation can easily be improved by not enforcing REALLY_SLOW_IO.
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This doesn't completely address the issue - Xen just cannot guarantee
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scheduling of a particular vCPU with a maximum latency of about 80us
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(needed for the default FIFO threshold value of 10). The only complete
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solution would require making ISA DMA usable on Xen.
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--- head-2010-03-24.orig/drivers/block/floppy.c 2010-03-24 13:43:18.000000000 +0100
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+++ head-2010-03-24/drivers/block/floppy.c 2010-03-25 14:39:44.000000000 +0100
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@@ -146,7 +146,9 @@
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#undef FLOPPY_SILENT_DCL_CLEAR
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+#ifndef CONFIG_XEN
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#define REALLY_SLOW_IO
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+#endif
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#define DEBUGT 2
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