JP2001243174A - Bus system and wrong operation prevention device for bus system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mask unauthorized access from a second vicarious operation means (PCI agent) so as to prevent wrong operation of a first vicarious operation means (host agent). SOLUTION: Unauthorized access from a PCI agent 2 is masked after or during execution of a system configuration cycle for a PCI agent 2 by a host agent 1 so as to prevent wrong operation of the host agent 1 by unauthorized access from the PCI agent 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus system for eliminating a system malfunction by using a PCI (Peripheral Component Interconnect) bus which is a standardized bus, and a malfunction prevention device for the bus system.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional bus system. In FIG. 5, a PCI bus 200, which is a system bus, includes a host agent 50, which is a first work substitute means for initializing the PCI bus 200 at the time of startup, and
It is composed of PCI agents 51 and 52 which are second work substitute means initialized by the host agent 50. The host / CPU 56 and the host memory 54 are on the host / CPU bus 206. The host CPU bus 207 and the host CPU 56 are connected to the internal bus 20.
6 and the host CPU bus 207 and the host memory 54 are connected by the internal bus 205. Further, the host CPU bus 207 and the host bridge circuit 53 are connected by the internal bus 204.

The host bridge circuit 53 of the host agent 50 is connected to the PCI bus 200 and the bridge circuits 57 and 58 in the PCI agents 51 and 52. The host agent 50 responds to the system configuration registers of the PCI agents 51 and 52 with the “hardware
Settings such as "resource (address of PCI space)" and "operation method".

Further, in this system, the bus master at the time of data transfer is the two of the host agents 51 and 52.
PCI agents 51 and 5
2 can also be a bus master. PCI Agent 5
When granting the bus master to PCs 1, 52, the PC
It is necessary to set the bus master by the command register at the address 04 of the configuration register of the I-agents 51 and 52.

[0005] In the PCI agents 51 and 52, as soon as the bus master is set, there is a PCI agent which becomes a PCI bus master and accesses the PCI bus master. host·
The bridge circuit 53 is configured so that the PCI system bus
In some cases, the configuration register is displayed at the address, or an illegal access is recognized as a normal access.

[0006]

However, in the conventional bus system, a malfunction may occur in the host agent 50 in any case.
For example, in the former case, since the configuration register of the host bridge circuit 53 is rewritten and the operation method and the like are rewritten, a failure such as a failure to become a bus master of the PCI bus 200 may occur. . In the latter case, the host / CPU bus 206
The contents of the host memory 54 above may be rewritten or an access to an area where no device exists may be performed by the host CP.
It may be generated by an instruction from the host CPU 4 on the U bus.

[0007] It is an object of the present invention to provide a first work substitute means,
An object of the present invention is to prevent an erroneous access of the first work substituting means by masking an unauthorized access from the second work substituting means after or during the execution of the configuration cycle of the second work substituting means.

[0008]

A bus system according to the present invention has a host bridge circuit in which a system bus and a host of a computer are connected by a first type bus, and a specific user is connected via the host bridge circuit. First work substituting means for substituting the work of the user, and a plurality of bridge circuits connected by a system bus and a second type bus, and a second substituting the user's work through these bridge circuits. A mask is provided in the work substituting means and the first work substituting means for preventing any address from being illegally accessed in the second work substituting means when the first work substituting means starts up the system. Unauthorized access blocking means. Thus, the first work substitute means masks an unauthorized access from the second work substitute means after executing the system configuration cycle of the second work substitute means or during execution, and The first work substitute means is prevented from malfunctioning due to the unauthorized access by the substitute means.

In the bus system according to the present invention, an area to be masked by the first work substituting means in order to prevent access from the second work substituting means during a system configuration cycle is stored in a system configuration register. In this case, malfunctions due to writing in these system configuration registers are prevented. This prevents the first work substituting means from malfunctioning due to the unauthorized access by the second work substituting means.

In the bus system of the present invention, when it is not necessary to prevent unauthorized access by unauthorized access blocking means,
It has a mask release unit for releasing the mask. This allows
When there is no need to prevent unauthorized access by the unauthorized access blocking means, the mask for the second work proxy means is released.

A malfunction preventing device for a bus system according to the present invention has a host bridge circuit in which a system bus and a host of a computer are connected by a first type bus, and performs user's work on behalf of the host bridge circuit. A first work substituting means, a second work substituting means having a bridge circuit connected to the system bus by a second type bus, and performing a user's work through the bridge circuit; The first work substituting means masks the second work substituting means in order to prevent the second work substituting means from illegally accessing any address when the system is started. An access blocking means is provided. Thus, the first work surrogate means masks the unauthorized access from the second work surrogate means after or during the execution of the configuration cycle of the second work surrogate means, and performs the second work surrogate means. The first work substitute means is prevented from malfunctioning due to unauthorized access by the means.

According to the malfunction prevention apparatus for a bus system of the present invention, the first work substitute means masks an area for masking access from the second work substitute means in a system configuration cycle. To prevent malfunction due to writing in these system configuration registers. This prevents the first work substituting means from malfunctioning due to unauthorized access by the second work substituting means. Also, it is possible to change the setting of the configuration register from another host agent via the system bus.

The malfunction preventing apparatus for a bus system according to the present invention has a mask releasing section for releasing a mask when there is no need to prevent unauthorized access by the unauthorized access blocking means. Thus, the mask is released by the mask release unit, so that the access by the second work substitute means is normally performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention.

In FIG. 1, a host agent 1 as a first work substitute means is a PCI which is a system bus.
When the system is started up on the bus 100, the PCI agent 2, which is the second work substitute means, is initialized.

The host agent 1 and the PCI agent 2 are agents that become bus masters in the PCI bus 100. Inside the host agent 1, a host bridge circuit 6 for executing a configuration cycle of the PCI bus 100, a host CPU 4 for controlling the host bridge circuit 6,
It comprises a host memory 5 for storing or displaying access data from the CI bus 100, and is connected to a host CPU bus 107. In addition, the host bridge circuit 6
PCI bus 100, PC in PCI agent 2
It is connected to the I · bridge circuit 8.

When the host bridge circuit 6 accesses from outside the PCI bus 100 while the configuration cycle of the PCI agent 2 is being executed, the unauthorized access detection unit 10 A function is provided for masking an area where a malfunction occurs when accessed by an agent. Note that the host CPU bus 107 and the host CPU 4 are connected by the internal bus 105,
The PU bus 107 and the host memory 5 are connected by the internal bus 106. Further, the host CPU bus 107 and the host bridge circuit 6 are connected by the internal bus 104.

FIG. 2 shows an example of a register for system configuration, which comprises a device ID, a vendor ID, a status, a command, a class code, a revision ID, and the like. FIG. 3 shows an example of a command of the system configuration register, which includes a bus master, a specification cycle, a memory space, an I / O space, and the like.

In the present system, the host agent 1 initializes the PCI configuration register of the PCI agent 2 connected to the PCI bus 100. The PCI agent 2 becomes a bus master of the PCI bus 100 during the configuration cycle (especially, after setting the command register of the configuration register and the “bus master”), and may illegally access the host agent 1. This unauthorized access may be an area where a malfunction occurs when accessed by the host agent 1 or an area where a malfunction occurs when the host bridge circuit 6 is accessed.

In the present embodiment, in order to prevent this, when an access is made from the PCI bus 100 during the configuration cycle of the host bridge circuit 6, the unauthorized access detecting means 10 serving as an unauthorized access preventing means includes a PCI agent. 2 decodes the address to be accessed and detects whether or not it is an area where a malfunction occurs for the host agent 1. As a result of the detection, if the area has a problem, the access to the area is masked to prevent the host agent 1 from malfunctioning.

A second embodiment of the present invention will be described. FIG. 4 is a block diagram of a second embodiment of the present invention.

Referring to FIG. 4, unauthorized access preventing means 10
The second embodiment differs from the first embodiment in that a mask release unit 11 for releasing a mask when there is no need to prevent unauthorized access due to the first embodiment is provided. The other components are denoted by the same reference numerals, and detailed description is omitted.

When no unauthorized access is made by the unauthorized access prevention means 10 by the mask release unit 11, the mask is released and the access by the second work substitute means can be performed normally.

FIG. 2 shows the operation of the second embodiment of the present invention.
This will be described with reference to FIG. In FIG. 2, when the host bridge circuit 6 accesses from outside the PCI bus 100 during the execution of the configuration cycle of the PCI agent 2, the unauthorized access detection unit 10 Is an access to an area that causes a malfunction when accessed by the host agent 1, this is masked.

The mask release unit 11 receives the command determined in advance, and allows the host bridge circuit 6 to operate the PCI bus 10 even during the configuration cycle.
In a configuration having a function of changing settings from another host agent, the host agent 1
Initializes the PCI configuration register of the PCI agent 2 connected to the PCI bus 100.

During the configuration cycle (particularly, the command register of the configuration register, the “bus master”)
After setting, for example), it may become a bus master of the PCI bus 3 and illegally access the host agent 1.
When this unauthorized access is made to the host agent 1, a malfunction may occur in an area where a malfunction occurs or in the host bridge circuit 6.

In the present embodiment, in order to prevent this, if there is an access from the PCI bus 100 during the configuration cycle of the host bridge circuit 6, the unauthorized access detection unit 10 causes the PCI agent 2 to try to access. The address is decoded to detect whether or not the address is an area where a malfunction occurs for the host agent 1. As a result of the detection, if the area has a problem, the access to the area is masked to prevent the host agent 1 from malfunctioning. When the configuration register of the host bridge circuit 6 is to be changed even during the configuration cycle of the host bridge circuit 6, the mask can be released by inputting a predetermined command to the mask release unit 11.

In the embodiment described above, when there is an access from the PCI bus 100 during the configuration cycle of the host bridge circuit 6, the unauthorized access detection unit 10 detects the unauthorized access and prevents the unauthorized access. However, it is needless to say that the present invention is not limited to this, and unauthorized access may be prevented by other means within a range not departing from the gist of the present invention.

[0029]

As described above in detail, according to the present invention, the area where the first work substituting means masks to prevent access from the second work substituting means in the system configuration cycle is set in the system configuration. In this case, malfunctions due to writing in these system configuration registers can be prevented. Further, it is possible to change the setting of the configuration register from another host agent via the system bus, and to release a mask for releasing malfunction prevention.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 illustrates a configuration example of a configuration register.

FIG. 3 illustrates an example of a command used for a configuration register.

FIG. 4 is a block diagram of a second embodiment of the present invention.

FIG. 5 is a block diagram of a conventional bus system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Host agent (1st work substitute means) 2 PCI agent (2nd work substitute means) 6 Host bridge circuit 8 PCI bridge circuit 10 Unauthorized access detection unit (Unauthorized access prevention unit) 11 Mask release unit 100 PCI bus (system bus) 101 First type bus 102, 103 Second type bus

Claims (6)

[Claims] 1. A host bridge circuit for connecting a system bus to a host side of a computer, and a first user who performs work of a specific user through the host bridge circuit.
A second work substituting means having a plurality of bridge circuits connected to the system bus, and substituting a user's work through these bridge circuits; and a first work substituting means. A bus system provided with an unauthorized access blocking means for masking an arbitrary address in the second work proxy means when the first work proxy means accesses the system at the time of starting the system; . 2. The system according to claim 1, wherein said first work substituting means masks an area for preventing access from said second work substituting means during a system configuration cycle by said unauthorized access preventing means. 2. The bus system according to claim 1, wherein only the above-mentioned registers are used to prevent a malfunction at the time of writing the registers for system configuration. 3. The bus system according to claim 1, further comprising a mask release unit that releases the mask when it is not necessary to prevent unauthorized access by the unauthorized access prevention unit. 4. A first work substituting means having a host bridge circuit for connecting a system bus and a host side of a computer, and performing a user's work through the host bridge circuit, and connected to the system bus. A second work substituting means having a bridge circuit, and substituting a user's work through the bridge circuit; and the first work substituting means, the first work substituting means, A bus system malfunction prevention device comprising an unauthorized access prevention device for masking the second work proxy device so as to prevent an arbitrary address from being illegally accessed in the second work proxy device. apparatus. 5. An area for masking the first work surrogate means for blocking access from the second work surrogate means at the time of a system configuration cycle by the unauthorized access prevention means is used for system configuration. 6. The malfunction preventing device for a bus system according to claim 5, wherein the malfunction is prevented when the register for system configuration is written. 6. The malfunction prevention device for a bus system according to claim 4, further comprising a mask release unit that releases the mask when there is no need to prevent unauthorized access by the unauthorized access prevention unit.