Mechanism to extend computer memory protection schemes

A mechanism in a microprocessor for enabling a translation lookaside buffer (TLB) to extend protection schemes of virtual memory pages, the mechanism comprising:

• a memory management unit, for accessing the virtual memory pages, said memory management unit comprising:
• TLB entries, for prescribing the protection schemes of the virtual memory pages, wherein an extended flags field within each of said TLB entries extends protection scheme indications provided for by an existing flags field;
• and
• extended protection logic, coupled to said TLB entries, configured to prescribe a legacy protection scheme according to said existing flags field or an extended protection scheme according to said existing flags field in combination with said extended flags field, wherein said extended flags field provides for further definition of said protection scheme indications provided for by said existing flags field, and wherein said legacy protection scheme is backwards-compatible with a legacy virtual page access protocol.

A computer program product for use with a computing device, the computer program product comprising:

• a computer usable medium, having computer readable program code embodied in said medium, for causing a CPU to be described, said CPU being capable of accessing virtual memory pages according to a legacy protection scheme and an extended protection scheme, said computer readable program code comprising:
• first program code, for describing a translation lookaside buffer (TLB), said TLB configured to store TLB entries, each having an existing flags field and an extended flags field;
• and
• second program code, for describing extended protection logic, said extended protection logic configured to specify said legacy protection scheme according to said existing flags field and said extended protection scheme according to said existing flags field in combination with said extended flags field, wherein said extended flags field provides for further restriction of access privileges indicated by said existing flags field, and whereby specification of said legacy protection scheme preserves compatibility with a legacy page access protocol.

A computer data signal embodied in a transmission medium, comprising:

• first computer-readable program code, for describing a translation lookaside buffer (TLB), said TLB configured to store TLB entries, each having an existing flags field and an extended flags field;
• second computer-readable program code, for describing extended protection logic, said extended protection logic configured to specify a legacy protection scheme according to said existing flags field and an extended protection scheme according to said existing flags field in combination with said extended flags field, wherein said extended flags field specifies further restriction of access privileges specified according to said existing flags field;
• and
• third computer-readable program code, for describing access logic, said access logic configured to access virtual memory pages, wherein, if a legacy access protocol is employed, said virtual memory pages are accessed in accordance with said legacy protection scheme.

A method for accessing a virtual memory page comprising:

• reading a first flags field from a translation lookaside buffer (TLB) entry, the first flags field preserving compatibility with a legacy virtual page access protocol by specifying legacy access restrictions in accordance with the protocol;
• reading a second flags field from the TLB entry, said second flags field in combination with the first flags field specifying extended access restrictions;
• and
• further restricting the legacy access restrictions specified by the first flags field according to the second flags field.