Abstract:
A method and apparatus for non-contiguous translation protection table that includes one or more first registers, two or more second registers, an address translator, and a detector. Each first register contains a value denoting a size of each of two or more blocks of memory. Each second register contains a value denoting the starting physical address of an associated one of the two or more blocks of memory. The address translator receives a virtual address and translates the virtual address to a physical address of one of the two or more blocks of memory. The detector detects whether the received virtual address is outside of the range of the two or more blocks of memory. The blocks of memory may be translation protection tables that reside in physically non-contiguous memory locations.

Description:
BACKGROUND  
         [0001]    1. Field  
           [0002]    This invention relates to memory address translation, and more specifically to non-contiguous address translation tables in memory.  
           [0003]    2. Background  
           [0004]    A switched fabric network system may use a scheme of a translation protection table (TPT) for all memory registration. This table may be created in system memory, and allows a device to read the table to gain access to a physical address, converted from a virtual address, for storage locations.  
           [0005]    [0005]FIG. 1 shows a block diagram of elements existing at a processor node in a switched fabric system. An operating system  10  may communicate with a channel adaptor  12  to get a physical address translation. A channel adaptor  12  (e.g. host channel adaptor (HCA), target channel adaptor (TCA), etc.) may use a system memory  14  resident translation protection table in order to convert virtual addresses used by applications into physical addresses used by the channel adaptor  12 . In current channel adaptor designs, this table is required to be entirely contiguous in physical memory. Therefore, the operating system is required to lock a large piece of physical memory and keep it locked during all operations carried out by the channel adaptor.  
           [0006]    [0006]FIG. 2 shows a diagram of connections between a channel adaptor and a contiguous TPT table. The dotted line separates the channel adaptor logic  12  from system memory  14 . System memory  14  contains a translation protection table  16 . Channel adaptor  12  includes a register  18  containing the table size, a register  20  containing the base physical address of the table, a comparator  22 , and an adder  24 . The channel adaptor hardware tracks the table size of TPT table  16  as well as the base physical address. The index is a portion of a virtual address from the operating system. Comparator  22  compares the received index with the table size stored in register  18  to determine if the index is out of the bounds of TPT table  16 , and if so, generates an “index out of bounds” error. If the index is not out of bounds, the address stored in register  20  is added to the index by adder  24  generating a physical address to TPT table  16 . A channel adapter stores information not only associated with the base of the to TPT table  16 , but also the number of entries in the table. For any given index into the TPT table, the channel adaptor is able to locate the physical address of the appropriate entry in the table as well as check the entry as outside the bounds of the TPT table.  
           [0007]    TPT table  16  is a fixed size. However, the operating system may need, during the course of operation, to change the initial set up for the TPT table (e.g., in order to map additional memory pages for a recently started application). A problem exists if the operating system desires to grow the one and only TPT table in the system when it is currently being used by the channel adaptor. The operating system has two options to possibly solve this problem. First, the operating system may flush the current TPT table and move the entire table to a larger contiguous location in system memory (to allow for more entries to be mapped). This larger location may be very large, e.g., supporting mapping for 2 27 −1 physical pages of memory. A TPT table supporting even a fraction of this memory map can easily be gigabytes in size.  
           [0008]    Second, the operating system may stop operations on the channel adaptor long enough to free up or rearrange the current TPT table to make room for the newly requested page mappings. Neither of these two options is desirable. The first option is unlikely to be able to locate a large portion of contiguous system memory that can fit the bigger TPT table. The second would require operations on the channel adaptor to be halted for a period of time while the TPT table is reorganized. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The present invention is further described in the detailed description which follows in reference to the noted plurality of drawings by way of non-limiting examples of embodiments of the present invention in which like reference numerals represent similar parts throughout the several views of the drawings and wherein:  
         [0010]    [0010]FIG. 1 is a block diagram of elements existing at a processor node in a switched fabric system;  
         [0011]    [0011]FIG. 2 is a diagram of connections between a channel adaptor and a contiguous TPT table;  
         [0012]    [0012]FIG. 3 is a diagram of a channel adaptor interfacing to a series of TPT table segments according to an example embodiment of the present invention; and  
         [0013]    [0013]FIG. 4 is a diagram of a channel adaptor interfacing to a series of TPT table segments according to another example embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0014]    The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention. The description taken with the drawings make it apparent to those skilled in the art how the present invention may be embodied in practice.  
         [0015]    Further, arrangements may be shown in block diagram form in order to avoid obscuring the invention, and also in view of the fact that specifics with respect to implementation of such block diagram arrangements is highly dependent upon the platform within which the present invention is to be implemented, i.e., specifics should be well within purview of one skilled in the art. Where specific details (e.g., circuits, flowcharts) are set forth in order to describe example embodiments of the invention, it should be apparent to one skilled in the art that the invention can be practiced without these specific details. Finally, it should be apparent that any combination of hard-wired circuitry and software instructions can be used to implement embodiments of the present invention, i.e., the present invention is not limited to any specific combination of hardware circuitry and software instructions.  
         [0016]    Although example embodiments of the present invention may be described using an example system block diagram in an example host unit environment, practice of the invention is not limited thereto, i.e., the invention may be able to be practiced with other types of systems, and in other types of environments (e.g., servers).  
         [0017]    Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.  
         [0018]    The present invention relates to method and apparatus for non-contiguous translation protection table where the translation protection table may consist of multiple translation tables that reside in physically non-contiguous memory locations. Moreover, the multiple translation tables may be of varying sizes, or may all be of the same size. A channel adapter storing information about multiple translation protection table segments allows for a more flexible software usage model of the TPT table with relatively minor hardware overhead.  
         [0019]    [0019]FIG. 3 shows a diagram of a channel adaptor interfacing to a series of translation protection table segments according to an example embodiment of the present invention. In this example embodiment, the translation protection table consists of multiple segments,  62  through  68 . Each individual translation protection table segment may be treated just like the translation protection table discussed and shown in FIG. 2 previously (i.e. occupy physically contiguous system memory locations, channel adaptor maintains information regarding the base address and a number of entries for each, etc.). The channel adaptor in this example embodiment is programmed such that each translation protection table segment may be accessed like a single contiguous translation protection table. For example, an index not found in the first TPT table (e.g. TPT table  62 ) may be checked for in the next logical TPT table (e.g. TPT table  64 ) just as if the two segments were physically contiguous.  
         [0020]    Each TPT table segment,  62 - 68 , has an associated table size and base address. TPT tables  62 -through  68  have table size registers  40  through  46  associated, and base address registers  48  through  54  associated respectively.  
         [0021]    For a given index into the TPT table, the channel adaptor may be required to determine which TPT table segment contains the specific entry and perform the appropriate bounds checking. This function becomes more complicated than in the single TPT case described previously. The out of bounds check done by comparator  60  takes into account the size of all the segments in use. A summation of the table size values stored in registers  40  through  46  is performed by adder  58  and the result compared to the index by comparator  60 .  
         [0022]    The range comparison logic consists of a series of arithmetic and comparison functions used to determine which segment contains the given TPT table entry. Table size registers  40  through  46  and base address registers  48  through  54  are connected to range comparison logic  56 . Range comparison logic  56  receives the index and determines which TPT table segment the index is addressing. Generation of the correct physical address needs to take into account the size of the segments logically ahead of the segment containing the index. For example, an index accessing a TPT table entry in TPT table segment  64  may have a physical address calculated as follows: index−table size of table segment  62 +base address of table segment  64 =physical address of TPT table entry. Therefore, after the range is checked, the index is added to the appropriate base after subtracting out the previous TPT table size(s). Each TPT table segment,  62  through  68 , may be created in memory as needed. Further, the last TPT table segment, i.e.  68 , may be grown or expanded if necessary. This is advantageous in that while the last TPT table segment may be grown, the remaining TPT segments may remain unchanged and in use by the channel adapter.  
         [0023]    [0023]FIG. 4 shows a diagram of a channel adaptor interfacing to a series of translation protection table segments according to another example embodiment of the present invention. In this example embodiment, the size of each TPT table segment may be fixed for the channel adaptor. Therefore, all TPT table segments for this channel adaptor use the same number of entries. This reduces the channel adapter hardware logic required for performing bounds checking and determining which TPT table segment contains the specific entry identified by the received index.  
         [0024]    At As shown in FIG. 4, hardware is reduced since only one register  80  holding a table size value may be required. The table size in register  80  is still compared with the index by comparator  88  to determine if the index is out of bounds of the TPT table segments  102  through  108 . Each TPT table segment,  102  through  108 , is the same size. This is the table size stored in register  80  divided by the number of TPT table segments. In this example embodiment of the present invention, each of TPT table segments,  102 ,  104 ,  106 ,  108 , have a size of the table size in register  80  divided by four, since there are four TPT table segments.  
         [0025]    The channel adaptor logic in this example embodiment also contains a register  84  that contains one enable bit for each of TPT table segments  102  through  108 . This enable bit may be set by a software making register  84  a programmable register. The enable bits inform the channel adaptor hardware whether a particular TPT segment is active. Software may take advantage of this feature in the channel adaptor as needed. Disabling all of the supported TPT table segments above the first segment, i.e., segment  102 , results in one physically contiguous TPT table in system memory as is used in current systems (e.g., FIG. 2).  
         [0026]    The channel adaptor embodiment shown in FIG. 4 also supports four base address registers  92  through  98 . Each register may be programmed to take into account the subtraction of the previous TPT table segments. For example, the base address contained in register  92  may equal the starting physical address of TPT table  102 . The base address stored in register  94  may equal the starting physical address to TPT table  104 −the TPT table size stored in register  80 / 4 . The base address contained in register  96  may equal the starting physical address of TPT table segment  106 —2 times the TPT table size stored in register  80 / 4 . Finally, base address stored in register  98  may equal the starting physical address of TPT table segment  108 —3 times the TPT table size stored in register  80 / 4 .  
         [0027]    This programming allows the hardware to minimize the number of arithmetic functions required to derive the physical address associated with any given index into the TPT table. As shown in FIG. 4, the index out of bounds and physical address of TPT table entry generation are similar to that shown in FIG. 2. The bit shifter  82 , adder  100 , and multiplexer  90  form range comparison logic. Bit shifter  82  may be used to select which of the TPT table segments the given index is accessing. Bit shifter  82  receives the index into the TPT table and receives the size table value in register  80  as inputs and produces a two bit select used to multiplex the contents of the four base address registers  92  through  98  to adder  100 . Bit shifter  82  accomplishes this by using the two bits of the received index which correspond to the two most significant bits of the programmed TPT table size in register  80 , normalized to a zero based index. For example, if the TPT table size in register  80  is 0×1000, containing entries 0×0000 through 0×0FFF, this suggests that each TPT table segment contains one quarter of these entries. This is shown in the following table:  
                                                           Segment   TPT Table Entries   Bit 11   Bit 10                           102   0x0000 - 0x03FF   0   0           104   0x0400 - 0x07FF   0   1           106   0x0800 - 0x0BFF   1   0           108   0x0C00 - 0x0FFF   1   1                      
 
         [0028]    In the example embodiment shown in FIG. 4, bits  11  and  10  of the index provide a convenient select for the appropriate base address register. Bit shifter  82  outputs bits  11  and  10  of the index that are used as selects to multiplexer  90 . The channel adaptor hardware in the embodiment shown in FIG. 4 illuminates the complex comparison and arithmetic operations that may be required in the example embodiment shown in FIG. 3. This is accomplished by using bit shifter  82  and careful software programming of the base address and TPT size register. Bit shifter  82  also provides a convenient way to check the enables associated with each TPT table segment,  102  through  108 . The channel adaptor maintains four bit register  84  indicating which TPT table segments are currently valid. As shown in FIG. 4, TPT table segment  106  is currently disabled, as illustrated by the enable bit in the upper left hand corner of TPT table segment  106  being equal to zero. Indices that attempt to access TPT table segment  106  may be detected by comparing the enable bits to the output of bit shifter  82 . This may be performed by detector  86  that outputs an error signal (access to disabled segment) for indices that attempt to access a TPT table segment that is currently not enabled.  
         [0029]    Methods and apparatus according to the present invention are advantageous in that the hardware and the channel adaptor is simpler, flexible, and saves cost by reducing gate count, complexity to test, etc. The present invention eliminates problems encountered in current channel adaptor implementations by providing channel adaptor support for a non-physically contiguous TPT table in system memory. According to the present invention, a channel adaptor contains programmable information associated with not one, but multiple TPT table segments. Each segment is treated as logically contiguous from the channel adapters point of view, but may be located anywhere within system memory. This allows an operating system to scale the size of a TPT table by essentially “stacking” new smaller pieces of logically contiguous memory on top of the previous configured TPT table. These smaller portions are not only more likely to be found available in system memory but they may also be added to the TPT table dynamically without interrupting channel adapter operations.  
         [0030]    It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to a preferred embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular methods, materials, and embodiments, the present invention is not intended to be limited to the particulars disclosed herein, rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.