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| This is a proposal for a simple flash emulation on QEMU/KVM.
| | PC System Flash emulation was added for QEMU in pc-1.1. |
| | |
| | =Flash Hardware= |
| | Uses CFI flash support in hw/pflash_cfi01.c. |
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| =Command line interface= | | =Command line interface= |
| To enable saving of the flash contents, a -flash
| | Usage of -bios and -pflash parameters as of pc-1.1: |
| a command line parameter would be added. This parameter
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| normally will override the -bios file usage.
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| | |
| <Pre>
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| -flash path path to filename for saving flash contents | |
| </Pre>
| |
| | |
| If the flash path does not exist, then the -bios file will be read to
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| initialize the flash contents. If the flash path does exist, then it
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| will be used instead of the -bios file contents.
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| | |
| =VM hardware interface=
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| ==Hardware resources==
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| The flash will be available as memory mapped io just below 0x100000000 (4GB). For example, if the -flash file was 0x100000 (1MB) in size, then the flash will be available in memory space from 0xfff00000 through 0xffffffff.
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| | |
| ==Normal reads==
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| The flash content can be read in 1, 2, 4 or 8 byte sizes like the
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| current read-only bios rom. The read accesses are not required to be aligned.
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| ==Programming interface== | | {| class='wikitable' border=1 |
| Aside from normal flash read operations, the flash can be communicated
| | ! KVM enabled !! -pflash used !! -bios used !! Result |
| with via special sequences of memory read and write operations.
| | |- |
| | |rowspan=3 | <Center>No</Center> |
| | | <Center>Yes</Center> || <Center>-</Center> |
| | | -pflash parameter will be loaded as flash image just below 4GB. |
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| This interface supports 32-bit aligned 32-bit data operations as
| | 'bios.bin' and -bios parameter will be ''ignored''. |
| well as 64-bit aligned 64-bit operations.
| | |- |
| | | <Center>No</Center> || <Center>No</Center> |
| | | 'bios.bin' will be used to create a read-only pflash drive. |
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| In the following examples, the address 0xfffffffc is used for 32-bit
| | A flash device is available, but it is read-only. |
| examples, and 0xfffffff8 is used for 64-bit examples. However,
| | |- |
| any properly aligned address can be used from 0x100000000-sizeof(bios.bin)
| | | <Center>No</Center> || <Center>Yes</Center> |
| up through 0xfffffff8 (for 64-bit operations) or 0xfffffffc (for 32-bit
| | | -bios parameter will be used to create a read-only pflash drive. |
| operations).
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| Only 1 flash communication operation can occur at one time. If any
| | A flash device is available, but it is read-only. |
| flash write occurs in another area of the flash, the the previous
| | |- |
| operation will be cancelled.
| | |rowspan=3 | <Center>Yes</Center> |
| | || <Center>Yes</Center> || <Center>-</Center> |
| | | An error message condition: |
|
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| ===Entering flash communication mode===
| | PC system firmware (pflash) not available |
| 32-bit access:
| | |- |
| <Pre> | | || <Center>No</Center> || <Center>No</Center> |
| write32(addr=0xfffffffc, data=0x5a5a5a5a)
| | | 'bios.bin' will be loaded as rom image. |
| read32(addr=0xfffffffc) => returns 0xa5a5a5a5
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| </Pre> | |
| 64-bit access:
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| <Pre> | |
| write64(addr=0xfffffff8, data=0x5a5a5a5a5a5a5a5a)
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| read64(addr=0xfffffff8) => returns 0xa5a5a5a5a5a5a5a5
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| </Pre> | |
|
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|
| ===Program flash===
| | No system flash is available. |
| * The flash must be in flash communication mode
| | |- |
| 32-bit access:
| | | <Center>No</Center> || <Center>Yes</Center> |
| <Pre> | | | -bios parameter filename will be loaded as rom image. |
| write32(addr=0xfffffffc, data=0x0)
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| read32(addr=0xfffffffc) => returns current flash contents
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| write32(addr=0xfffffffc, data=new flash contents)
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| read32(addr=0xfffffffc) => returns new flash contents
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| read32(addr=0xfffffffc) => returns new flash contents ^ 0xffffffff
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| </Pre> | |
| 64-bit access:
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| <Pre> | |
| write64(addr=0xfffffff8, data=0x0)
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| read64(addr=0xfffffff8) => returns current flash contents
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| write64(addr=0xfffffff8, data=new flash contents)
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| read64(addr=0xfffffff8) => returns new flash contents
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| read64(addr=0xfffffff8) => returns new flash contents ^ 0xffffffffffffffff
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| </Pre> | |
| * Following a successful program operation, the flash will immediately return to normal read mode.
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|
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|
| ===Flash size read===
| | No system flash is available. |
| * The flash must be in flash communication mode
| | |} |
| 32-bit access:
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| <Pre>
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| write32(addr=0xfffffffc, data=0x1)
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| read32(addr=0xfffffffc) => returns the size of the flash device
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| read32(addr=0xfffffffc) => returns the flash size ^ 0xffffffff
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| </Pre>
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| 64-bit access:
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| <Pre>
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| write64(addr=0xfffffff8, data=0x1)
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| read64(addr=0xfffffff8) => returns the size of the flash device
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| read64(addr=0xfffffff8) => returns the flash size ^ 0xffffffffffffffff
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| </Pre>
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| * Following a flash size read operation, the flash will immediately return to normal read mode.
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|
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| ===Interruptions=== | | ==pflash drives== |
| * If the sequences above are not followed exactly, then the flash device should cancel the operation and immediately enter read mode.
| | The flash image can be any drive image format supported by QEMU. |
| * If a non-aligned write operation or a 1 or 2 byte write occurs to the flash while a flash operation is in progress, then the current operation is immediately cancelled.
| |
| * If a properly aligned write operation occurs to an different address or of a different size while another operation is in progress, then the current operation is immediately cancelled. If the write was the proper value to begin entering flash communication mode, then it will be accepted, and the sequence can proceed as a new operation.
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| ==Examples==
| | There are two ways to add the pflash drive when launching qemu-system-i386 or qemu-system-x86_64: |
| * 32-bit flash write example at address 0xffff0000. Data: old=0x76543210, new=0xfedcba98
| | # Use the -pflash parameter |
| <Pre>
| | # Use the -drive parameter with if=pflash |
| write32(addr=0xffff0000, data=0x5a5a5a5a)
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| read32(addr=0xffff0000) => returns 0xa5a5a5a5
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| write32(addr=0xffff0000, data=0x0)
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| read32(addr=0xffff0000) => returns 0x76543210
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| write32(addr=0xffff0000, data=0xfedcba98)
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| read32(addr=0xffff0000) => returns 0xfedcba98
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| read32(addr=0xffff0000) => returns 0x01234567
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| </Pre>
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|
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| * 64-bit read flash size example at address 0xffff0000. Flash size=0x100000
| | [[Category:Completed feature pages]] |
| <Pre>
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| write64(addr=0xffff0000, data=0x5a5a5a5a5a5a5a5a)
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| read64(addr=0xffff0000) => returns 0xa5a5a5a5a5a5a5a5
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| write64(addr=0xffff0000, data=0x1)
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| read64(addr=0xffff0000) => returns 0x0000000000100000
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| read64(addr=0xffff0000) => returns 0xffffffffffefffff
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| </Pre>
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