* Don Porter (por...@cs.unc.edu) wrote: > On 4/16/24 13:03, Peter Maydell wrote: > > On Tue, 16 Apr 2024 at 17:53, Don Porter <por...@cs.unc.edu> wrote: > > > There is still a lot I am learning about the code base, but it seems > > > that qemu_get_guest_memory_mapping() does most of what one would need. > > > It currently only returns the "leaves" of the page table tree in a list. > > > > > > What if I extend this function with an optional argument to either > > > 1) return the interior nodes of the page table in additional lists (and > > > then parse+print in the monitor code), or > > > 2) inline the monitor printing in the arch-specific hook, and pass a > > > flag to get_guest_memory_mapping() that turns on/off the statements that > > > pretty print the page tables? > > > > > > It looks like most CPUs implement this function as part of checkpointing. > > As far as I can see only x86 implements the get_memory_mapping > > function, so once again somebody has added some bit of > > functionality that does a walk of the page tables that is > > x86 only and that shares no code with any of the other > > page table walking code :-( > > My mistake - get_memory_mappings() is only implemented in x86. > > In doing some searching of the code, many architectures implement > mmu_translate() and > get_physical_address() functions, but they are not standardized. I also see > your larger point > about replicating page walking code in x86. > > I imagine you have something in mind that abstracts things like the height > of the radix tree, > entries per node, checking permissions, printing the contents, etc. > > Perhaps I should start by trying to merge the x86 page walking code into one > set of common > helper functions, get more feedback (perhaps on a new patch thread?), and > then consider > how to abstract across architectures after getting feedback on this? > > In looking at x86 code, I see the following places where there is page table > walking code to > potentially merge: > > * target/i386/monitor.c - existing info commands > > * target/i386/helper.c - get_phys_page_attrs_debug > > * target/i386/arch_memory_mapping.c - implements get_memory_mapping > > * tcg/sysemu/excp_helper.c: implements mmu_translate() and > get_physical_address()
One thing to keep in mind (although I don't know the x86 code) is that you want the monitor command not to change any state, nor to fail if there's a particularly screwy page table; so no flagging exceptions or flagging accessed bits or changing the state of the tcg. Dave > Thanks, > > Don > -- -----Open up your eyes, open up your mind, open up your code ------- / Dr. David Alan Gilbert | Running GNU/Linux | Happy \ \ dave @ treblig.org | | In Hex / \ _________________________|_____ http://www.treblig.org |_______/
