JPH0370260B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] This is an access control method for preserving the storage area of a computer system main storage device. When controlling write access to a main storage device that has a so-called memory protection key, if the memory protection key needs to be checked, reading and partial update operations of the key are started in parallel, and the result of the key check is , if access should be prohibited, the partial update operation is interrupted before the write operation is completed. This configuration reduces the average time required for write operations with memory protection,
In addition, control can be simplified.

[Industrial application field]

The present invention relates to an access control method for preserving the storage area of a main storage device in a computer system.

When a main storage device is used by multiple access source devices, a so-called memory protection key is provided for each storage area divided into a predetermined size in order to protect the contents of the storage area, etc. The access is executed only when there is a certain relationship, such as a match, between the so-called access key shown in the figure and the storage protection key for the access destination storage area, and when the predetermined relationship is not satisfied, the access is executed. The prohibition method is widely used.

In such a method, since reading and determining the storage protection key is required when accessing the main memory, the processing time tends to be longer than that of a simple access process, and the control tends to be complicated.

[Conventional technology]

FIG. 2 is a block diagram of an example of the configuration of a computer system.

The central processing unit 1 , channel processing unit 2 , etc. access the main storage device 4 via the storage control device 3 . The main memory device 4 consists of a main memory unit 5 that stores original main memory data and a key memory unit 6 that stores a memory protection key.

Each memory protection key is, for example, 4 bits, and has a storage area of 2 kilobytes in the main memory unit 5, for example.
Alternatively, it is provided for every 4 kilobytes. The key storage unit 6 has a capacity to store the necessary storage protection keys according to the capacity of the main storage unit 5, and is usually constructed of a memory faster than the main storage unit 5.

Access control for memory protection is performed when the access key specified in the access request is compared with the memory protection key for the storage area to be accessed, and the values of both satisfy a predetermined relationship as in the example above. , the requested access is executed, and if the relationship is not satisfied, the access is prohibited.

In response to demands for faster main memory access, the central processing unit 1 often handles the above-mentioned access control within itself, for example by having a buffer of memory protection keys within each unit. When performing access control for storage protection on access from the device 2 and the like, the storage control device 3 performs access control.

In that case, the access key is specified in the command for input/output processing from the central processing unit 1 to the channel processing unit 2. The channel processing device 2 holds this access key, and when accessing the main storage device 4 for input/output data transfer, uses the held access key as a parameter when requesting access to the storage control device 3. Specify as part.

FIG. 3 is a block diagram showing the configuration of the main parts of the storage control device 3. As shown in FIG.

In a request for access from the channel processing device 3 to the main storage device 4, request information such as designation of the access type and access destination storage address is set in the request buffer 10, and an access key is set in the key buffer 11.

Access types include "read", "write", "partial update", etc. Here, as is well known, a partial update refers to an update in which only a part of the content of one word, which is the read/write unit of the main memory unit 5, is changed, and the previous content is preserved for the other part. In that case, reading, updating, and writing are performed successively.

When an access request is set in the request buffer 10, as is well known, first, the busy check circuit 12 checks the busy display line 13 to determine whether the access destination, for example, a storage bank, is currently executing an access request from another device. The request information is checked against the information, and if it is free, the request information is transferred to the priority selection section 14.

The priority selection unit 14 has a configuration similar to that described above, and when there is access request information input simultaneously from other channel processing devices 2, central processing units 1, etc., the priority selection unit 14 selects one request among them according to a predetermined priority order. and transfers the request information to the key control unit 15.

The key control unit 15 sends a command to read the storage protection key of the storage area to which access is requested to the key storage unit 16 via the key readout control line 16, and transfers the read storage protection key to the key transfer line 11.
7 into the key register 18.

In the key control unit 15, the switch 19 selects the key buffer 11 for the request source currently being executed, and the comparison circuit 20 selects the key buffer 11 for the request source currently being executed.
Check against the contents of

As a result, for example, in the case of the access control method as exemplified above, if the values of both keys match or if the content of the key buffer 11 is 0, the access permission signal line 22 is turned on as the output of the comparison circuit 20. By doing so, the control of the access control section 21 is advanced and execution of access to the main storage unit 5 is started.

[Problem that the invention seeks to solve]

According to the above-mentioned conventional configuration, when executing an access request to the main storage device 4, the time for reading and checking the storage protection key is added to check the storage protection key, which reduces the effective efficiency from the perspective of the access request source. There is a problem that the access time becomes long.

[Means for solving problems]

FIG. 1 is a block diagram showing the configuration of the present invention.

In the figure, 30 is a key control section, 31 is an access control section, and according to the present invention, the key control section 30
and the access control unit 31 are activated in parallel by the priority selection unit 14. 32 is an access prohibition latch.

[Effect]

The priority selection unit 14 transfers the required information of the access request selected in the conventional manner to the key control unit 30 and the access control unit 31, respectively, and starts controlling both.

The key control section 30 accesses the key storage unit 6 in the same manner as in the prior art.

The access control section 31 accesses the main memory unit 5 in parallel with the key control section 30. However, in the case of a write request, the main memory unit 5 is always commanded to execute a partial update.

When the comparator circuit 20 of the key control unit 30 outputs the key comparison result, the access prohibition latch 32 is set to ON by means of a negative signal of the access permission signal, for example, if access is to be prohibited.

The output of the access prohibition latch 32 is transferred to the main memory unit 5, and the access control thereof is interrupted.

As described above, by using a faster memory than the main memory unit 5 for the key memory unit 6 as usual, when access is prohibited, the write operation in the main memory unit 5 is not executed and access is prohibited. If not, the partial update operation will be performed without any access control delay.
It becomes possible to improve the average access time.

〔Example〕

In FIG. 1, the process until the access request set in the request buffer 10 is selected by the priority selection section 14 is the same as the conventional one.

The priority selection unit 14 sends the required information of the selected access request to the key control unit 30 and the access control unit 3.
1 and start controlling both.

The key control unit 30 accesses the key storage unit 6 in the same way as in the conventional case, and receives the read storage protection key into the key register 18.

The access control section 31 accesses the main memory unit 5 in parallel with the key control section 30. However, in the case of a write request, the main memory unit 5 is always instructed to execute a partial update, and as a result, the main memory unit 5 first executes reading of the specified storage area, and then the read data is sent to the access control unit 31. The data is updated with write data (not shown) transferred from the storage area, and a write operation is performed to the original storage area.

When the comparison circuit 20 of the control section 30 outputs the key comparison result to the access permission signal line 33 as in the conventional case, the access prohibition latch 32 is set by, for example, a negative signal. That is, when access is prohibited, the output of the access prohibition latch 32 is turned on.

The output of the access inhibit latch 32 is transferred to the main memory unit 5, and if configured to interrupt its access control, this signal will inhibit the write operation following the read of the partial update operation, thus achieving access inhibition. . On the other hand, partial updates when access is not prohibited are executed without any delay due to access control, making it possible to improve the average access time.

The signal on the access permission signal line 33 indicating the key inspection result is set and held in the access permission latch 34, and the access type is set to, for example, "two consecutive
By providing "Write word", the access control unit 31 executes writing of the first word of this write operation as described above, and when the access permission latch is turned on, writes the second word. can be made to be a simple write operation without relying on partial updates. This configuration makes it possible to further shorten the effective access time.

In the case of a read request, the output of the access prohibition latch 32 is configured to inhibit the transfer of the read data to the access request source device by a circuit (not shown).

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in a computer system in which access control for storage protection is performed by a storage control device, an increase in effective access time due to the access control is suppressed, thereby improving system performance. It has a significant industrial effect of improving

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention;
The figure is a block diagram of an example of the configuration of a computer system.
The figure is a block diagram of an example of the configuration of a conventional system. In the figure, 1 is a central processing unit, 2 is a channel processing unit, 3 is a storage control unit, 4 is a main storage unit,
5 is a main memory unit, 6 is a key memory unit, 1
0 is a request buffer, 11 is a key buffer, 12 is a busy inspection circuit, 14 is a priority selection section, 15, 30
18 is a key control unit, 18 is a key register, 19 is a switch, 20 is a comparison circuit, 21 and 31 are access control units, 32 is an access prohibition latch, and 34 is an access permission latch.

Claims (1)

[Scope of Claims] 1. When a storage control device that controls access to a main storage device having a storage protection key processes a write access request from an access source device, partial update control of a storage area specified in the access request is performed. means 31 for starting the partial update control; means 30 for reading out a storage protection key corresponding to the storage area in parallel with the partial update control; and means 30 for reading the storage protection key corresponding to the storage area; A storage device access control system characterized by comprising means 32 for detecting that a value has a predetermined relationship and interrupting the partial update control.