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39 lines
1.6 KiB
39 lines
1.6 KiB
====================
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QEMU PCI test device
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====================
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``pci-testdev`` is a device used for testing low level IO.
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The device implements up to three BARs: BAR0, BAR1 and BAR2.
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Each of BAR 0+1 can be memory or IO. Guests must detect
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BAR types and act accordingly.
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BAR 0+1 size is up to 4K bytes each.
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BAR 0+1 starts with the following header:
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.. code-block:: c
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typedef struct PCITestDevHdr {
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uint8_t test; /* write-only, starts a given test number */
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uint8_t width_type; /*
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* read-only, type and width of access for a given test.
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* 1,2,4 for byte,word or long write.
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* any other value if test not supported on this BAR
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*/
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uint8_t pad0[2];
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uint32_t offset; /* read-only, offset in this BAR for a given test */
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uint32_t data; /* read-only, data to use for a given test */
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uint32_t count; /* for debugging. number of writes detected. */
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uint8_t name[]; /* for debugging. 0-terminated ASCII string. */
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} PCITestDevHdr;
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All registers are little endian.
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The device is expected to always implement tests 0 to N on each BAR, and to add new
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tests with higher numbers. In this way a guest can scan test numbers until it
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detects an access type that it does not support on this BAR, then stop.
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BAR2 is a 64bit memory BAR, without backing storage. It is disabled
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by default and can be enabled using the ``membar=<size>`` property. This
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can be used to test whether guests handle PCI BARs of a specific
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(possibly quite large) size correctly.
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