| Message ID | 20200504145810.11882-1-alexandre.chartre@oracle.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | ASI - Part II (Decorated Page-Table) | expand |
Hello Alexandre, On Mon, May 04, 2020 at 04:57:57PM +0200, Alexandre Chartre wrote: > This is part II of ASI RFC v4. Please refer to the cover letter of > part I for an overview the ASI RFC. > > https://lore.kernel.org/lkml/20200504144939.11318-1-alexandre.chartre@oracle.com/ > > This part introduces decorated page-table which encapsulate native page > table (e.g. a PGD) in order to provide convenient page-table management > functions, such as tracking address range mapped in a page-table or > safely handling references to another page-table. > > Decorated page-table can then be used to easily create and manage page > tables to be used with ASI. It will be used by the ASI test driver (see > part III) and later by KVM ASI. > > Decorated page-table is independent of ASI, and can potentially be used > anywhere a page-table is needed. This is very impressive work! I wonder why did you decide to make dpt x86-specific? Unless I've missed simething, the dpt implementation does not rely on anything architecture specific and can go straight to linux/mm. Another thing that comes to mind is that we already have a very decorated page table, which is mm_struct. I admit that my attempt to split out the core page table bits from the mm_struct [1] didn't went far, but I still think we need a first class abstraction for the page table that will be used by both user memory management and the management of the reduced kernel address spaces. [1] https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=pg_table/v0.0 > Thanks, > > alex. > > ----- > > Alexandre Chartre (13): > mm/x86: Introduce decorated page-table (dpt) > mm/dpt: Track buffers allocated for a decorated page-table > mm/dpt: Add decorated page-table entry offset functions > mm/dpt: Add decorated page-table entry allocation functions > mm/dpt: Add decorated page-table entry set functions > mm/dpt: Functions to populate a decorated page-table from a VA range > mm/dpt: Helper functions to map module into a decorated page-table > mm/dpt: Keep track of VA ranges mapped in a decorated page-table > mm/dpt: Functions to clear decorated page-table entries for a VA range > mm/dpt: Function to copy page-table entries for percpu buffer > mm/dpt: Add decorated page-table remap function > mm/dpt: Handle decorated page-table mapped range leaks and overlaps > mm/asi: Function to init decorated page-table with ASI core mappings > > arch/x86/include/asm/asi.h | 2 + > arch/x86/include/asm/dpt.h | 89 +++ > arch/x86/mm/Makefile | 2 +- > arch/x86/mm/asi.c | 57 ++ > arch/x86/mm/dpt.c | 1051 ++++++++++++++++++++++++++++++++++++ > 5 files changed, 1200 insertions(+), 1 deletion(-) > create mode 100644 arch/x86/include/asm/dpt.h > create mode 100644 arch/x86/mm/dpt.c > > -- > 2.18.2 >
On 5/14/20 11:29 AM, Mike Rapoport wrote: > Hello Alexandre, > > On Mon, May 04, 2020 at 04:57:57PM +0200, Alexandre Chartre wrote: >> This is part II of ASI RFC v4. Please refer to the cover letter of >> part I for an overview the ASI RFC. >> >> https://lore.kernel.org/lkml/20200504144939.11318-1-alexandre.chartre@oracle.com/ >> >> This part introduces decorated page-table which encapsulate native page >> table (e.g. a PGD) in order to provide convenient page-table management >> functions, such as tracking address range mapped in a page-table or >> safely handling references to another page-table. >> >> Decorated page-table can then be used to easily create and manage page >> tables to be used with ASI. It will be used by the ASI test driver (see >> part III) and later by KVM ASI. >> >> Decorated page-table is independent of ASI, and can potentially be used >> anywhere a page-table is needed. Hi Mike, > This is very impressive work! > > I wonder why did you decide to make dpt x86-specific? Unless I've missed > simething, the dpt implementation does not rely on anything architecture > specific and can go straight to linux/mm. Correct, this is not x86 specific. I put it in arch/x86 because that's currently the only place were I use it, but it can be moved to linux/mm. > Another thing that comes to mind is that we already have a very > decorated page table, which is mm_struct. mm_struct doesn't define a generic page-table encapsulation. mm_struct references a page table (i.e. PGD) and adds all kind of attributes needed for mm management but not necessarily related to page-table. > I admit that my attempt to > split out the core page table bits from the mm_struct [1] didn't went > far, but I still think we need a first class abstraction for the page > table that will be used by both user memory management and the > management of the reduced kernel address spaces. Agree. I remember your attempt to extract the page-table from mm_struct; this is not a simple work! For ASI, I didn't need mm, so it was simpler to built a simple decorated page-table without attempting to use with mm (at least for now). Thanks, alex. PS: if you want to play with dpt, there's a bug in dpt_destroy(), patch 08 adds a a double free of dpt->backend_pages pages. > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=pg_table/v0.0 > >> Thanks, >> >> alex. >> >> ----- >> >> Alexandre Chartre (13): >> mm/x86: Introduce decorated page-table (dpt) >> mm/dpt: Track buffers allocated for a decorated page-table >> mm/dpt: Add decorated page-table entry offset functions >> mm/dpt: Add decorated page-table entry allocation functions >> mm/dpt: Add decorated page-table entry set functions >> mm/dpt: Functions to populate a decorated page-table from a VA range >> mm/dpt: Helper functions to map module into a decorated page-table >> mm/dpt: Keep track of VA ranges mapped in a decorated page-table >> mm/dpt: Functions to clear decorated page-table entries for a VA range >> mm/dpt: Function to copy page-table entries for percpu buffer >> mm/dpt: Add decorated page-table remap function >> mm/dpt: Handle decorated page-table mapped range leaks and overlaps >> mm/asi: Function to init decorated page-table with ASI core mappings >> >> arch/x86/include/asm/asi.h | 2 + >> arch/x86/include/asm/dpt.h | 89 +++ >> arch/x86/mm/Makefile | 2 +- >> arch/x86/mm/asi.c | 57 ++ >> arch/x86/mm/dpt.c | 1051 ++++++++++++++++++++++++++++++++++++ >> 5 files changed, 1200 insertions(+), 1 deletion(-) >> create mode 100644 arch/x86/include/asm/dpt.h >> create mode 100644 arch/x86/mm/dpt.c >> >> -- >> 2.18.2 >> >