EP0327798A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Control method and apparatus for zero-origin data spaces
Assignee: International Business Machines Corp
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Filing: 1989-01-05
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Granted: —
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Expires: 2009-01-05
Abstract
Abstract Within a data processing system, a control method and mechanism for supporting a data space without common segments in addition to traditional address spaces containing common segments. The invention includes logic for eliminating duplication of lookaside table entries for virtual addresses within shared segments, but not for identical virtual addresses within data address spaces; it also provides for overriding low address protection for store operations into data spaces. Thus, it permits the entire virtual addressing range to be available to programs wishing to use such data spaces for data isolation and data sharing.
Inventors
- 👤 Casper Anthony Scalzi
- 👤 Richard John Schmalz
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 23:26
CPC Classifications
G; G06; G06F; G06F12/00; G06F12/14; G06F12/1458; G06F12/1466; G06F12/1475; G06F12/02; G06F12/08; G06F12/10; G06F12/1027; G06F12/1036
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
194 words
Mechanism for supporting two distinct address space types, a program address space type in which at least one segment of storage is common to all such address space types, and at least one segment of storage is unique to a particular address space of said address space type, and a data space type in which all segments of storage are unique to each address space of such address space type, in a central processing complex comprising a CPU, main storage, system resources connected to the CPU and to the main storage, and an operating system supporting a plurality of address spaces containing instructions and data, characterized by means for resolving virtual addresses within one of said address spaces into real addresses within main system storage, by a dynamic lookaside table having entries comprising virtual addresses and corresponding real addresses, said entries usable for bypassing said means for resolving virtual addresses, and by means for distinguishing between said program address spaces, which permit sharing of said entries among said address spaces of said address space type for addresses within said common segments, and said data spaces, which do not permit said sharing of said entries.
Claim 2
Dependent Claim
194 words
Mechanism for supporting two distinct address space types, a program address space type in which at least one segment of storage is common to all such address space types, and at least one segment of storage is unique to a particular address space of said address space type, and a data space type in which all segments of storage are unique to each address space of such address space type, in a central processing complex comprising a CPU, main storage, system resources connected to the CPU and to the main storage, and an operating system supporting a plurality of address spaces containing instructions and data, characterized by means for resolving virtual addresses within one of said address spaces into real addresses within main system storage, by a dynamic lookaside table having entries comprising virtual addresses and corresponding real addresses, said entries usable for bypassing said means for resolving virtual addresses, and by means for distinguishing between said program address spaces, which permit sharing of said entries among said address spaces of said address space type for addresses within said common segments, and said data spaces, which do not permit said sharing of said entries.
Claim 3
Dependent Claim
23 words
Mechanism of claim 1, characterized by means for overriding low address protection for store operations having a target located in a data space.
Claim 4
Dependent Claim
84 words
Mechanism of claim 1 or 2, characterized in that means for distinguishing between said program address spaces and said data spaces comprises a data space indicator located in a segment table descriptor (STD), said one of the descriptors being associated with each of said program address spaces and each of said data spaces, said data space indicator being active when the descriptor is associated with one of said data spaces, and inactive when the descriptor is associated with one of said program address spaces.
Claim 5
Dependent Claim
61 words
Mechanism of claim 2, characterized by means for overriding low address protection comprises said data space indicator inhibiting the generation of a low address protection exception when said indicator is active, and not inhibiting said exception when said indicator is inactive, and that means are available for accessing data within said data spaces from programs residing in said program address spaces.
Claim 6
Dependent Claim
43 words
Mechanism of claim 4, characterized in that the means for accessing data within said data spaces further comprises a segment table descriptor (STD) selection mechanism for associating one of said virtual addresses with a segment table associated with one of said data spaces.
Claim 7
Dependent Claim
149 words
Mechanism of one of claims 1 to 5, characterized in that the STD selection mechanism (STD) comprises a plurality of access register means each associated with a particular one of a plurality of general register means, each of said access register means having the capability of holding an access list entry token (ALET), an access list means containing access list entries (ALE's) each identified by an access list entry token (ALET), means for obtaining an access list entry (ALE) corresponding to an access list entry token (ALET) in one of said access register means, memory means for containing address space number second table entries (ASTE's), means for identifying an address space number second table entry (ASTE) from said access list entry (ALE) and for obtaining said address space number second table entry (ASTE), wherein said address space number second table entry (ASTE) contains a desired segment table descriptor (STD).
Claim 8
Dependent Claim
105 words
Method of translating virtual addresses to real addresses for the mechanism of claims 1 to 6, characterized by storing previously translated virtual addresses with corresponding real (main storage) addresses as entries in a translation lookaside buffer, and by using one of said entries to bypass a translation process if a virtual address to be translated matches a virtual address in one of said entries, and either both of said virtual addresses are associated with the same segment table descriptor, or both of said virtual addresses are associated with an address in a common segment of storage, and neither address is part of a data space.
Claim 9
Dependent Claim
51 words
Method of translating virtual addresses of claim 7, characterized by using the contents of an access register to obtain a segment table descriptor for use in translating addresses of said data for accessing data within one of said data spaces from a program executing in one of said program address spaces.
Claim 10
Dependent Claim
48 words
Method of claim 8 characterized by overriding a low address protection exception where said accessing data within a data space is by means of a store operation into an address within an address range of 0-511, and a control register indicates that said low address protection is active.
Claim 11
Dependent Claim
121 words
Method of claim 9 characterized in that for isolating data to be accessed by a program executing in one of said address spaces into one of said data spaces, that data from external storage into a contiguous section of the virtual addressing range of a data space are mapped to make said data directly addressable by said program, that data are operated, so that said operating causes portions of said data not yet read into main storage to be read in by the operating system, and that the data have been written back to external storage so that said writing causes physical I/O to occur only for data pages on which portions of said data have been changed by said operating.
References Cited (Backward Citations)
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