Sergey Fedorov <serge.f...@gmail.com> writes: > On 11/04/16 23:00, Sergey Fedorov wrote: >> On 05/04/16 18:32, Alex Bennée wrote: >> >> (snip) >>> + >>> +Memory maps and TLBs >>> +-------------------- >>> + >>> +The memory handling code is fairly critical to the speed of memory >>> +access in the emulated system. >>> + >> It would be nice to put some intro sentence for the following bullets :) >> >>> + - Memory regions (dividing up access to PIO, MMIO and RAM) >>> + - Dirty page tracking (for code gen, migration and display) >>> + - Virtual TLB (for translating guest address->real address) > > There's also a global page table - called 'l1_map' - which is used for: > * keeping a list of TBs generated from a given physical guest page for > further code invalidation on page writes > * holding a bitmap to track which regions of a given physical guest page > actually contain code for optimized code invalidation on page writes > (used only in system mode emulation) > * holding page flags, e.g. protection bits (used only in user mode > emulation) > > The page table seems to be protected by 'mmap_lock' in user mode > emulation but by 'tb_lock' in system mode emulation. It may turn to be > possible to read it safely even with no lock held.
I've started adding words to that effect to the document. > > Kind regards, > Sergey > >>> + >>> +There is a both a fast path walked by the generated code and a slow >>> +path when resolution is required. When the TLB tables are updated we >>> +need to ensure they are done in a safe way by bringing all executing >>> +threads to a halt before making the modifications. >> Again, I think we could benefit if we could possibly manage to avoid >> bringing vCPU threads to halt. >> >> Nothing about memory regions and dirty page tracking? >> >>> + >>> +DESIGN REQUIREMENTS: >>> + >>> + - TLB Flush All/Page >>> + - can be across-CPUs >>> + - will need all other CPUs brought to a halt >> s/will/may/ ? >> >>> + - TLB Update (update a CPUTLBEntry, via tlb_set_page_with_attrs) >>> + - This is a per-CPU table - by definition can't race >>> + - updated by it's own thread when the slow-path is forced >> (snip) > > Kind regards, > Sergey -- Alex Bennée
