| Message ID | 575d21dff52df4fa53d17e77728018453f82e8e5.1492384862.git.shorne@gmail.com |
|---|---|
| State | New |
| Headers | show |
On 04/16/2017 04:23 PM, Stafford Horne wrote: > When debugging in gdb you might want to inspect instructions in mapped > pages or in exception vectors like 0x800 etc. This was previously not > possible in qemu since the *get_phys_page_debug() routine only looked > into the data tlb. > > Change to fall back to look into instruction tlb and plain physical > pages. > > Signed-off-by: Stafford Horne <shorne@gmail.com> Oh the horrors of a software managed TLB. You might do well to architecturally define an SPR that holds the page table base, even if for real hardware that's only used by the software refill to load up the address. That would give qemu the option of performing a real page table walk. This would fix this debug hook properly (so that you can examine pages that aren't in the TLB at all). It would also optionally allow QEMU to skip the software refill, which *significantly* speeds up emulation. That said, Reviewed-by: Richard Henderson <rth@twiddle.net> r~
On Tue, Apr 18, 2017 at 12:47:30AM -0700, Richard Henderson wrote: > On 04/16/2017 04:23 PM, Stafford Horne wrote: > > When debugging in gdb you might want to inspect instructions in mapped > > pages or in exception vectors like 0x800 etc. This was previously not > > possible in qemu since the *get_phys_page_debug() routine only looked > > into the data tlb. > > > > Change to fall back to look into instruction tlb and plain physical > > pages. > > > > Signed-off-by: Stafford Horne <shorne@gmail.com> > > Oh the horrors of a software managed TLB. > > You might do well to architecturally define an SPR that holds the page table > base, even if for real hardware that's only used by the software refill to > load up the address. > > That would give qemu the option of performing a real page table walk. This > would fix this debug hook properly (so that you can examine pages that > aren't in the TLB at all). It would also optionally allow QEMU to skip the > software refill, which *significantly* speeds up emulation. Understood, I guess we would also need a way to represent which paging model we are using (1 level, 2 level etc)? > That said, > > Reviewed-by: Richard Henderson <rth@twiddle.net> Thanks for the review. -Stafford > > r~
On 04/18/2017 07:18 AM, Stafford Horne wrote: > On Tue, Apr 18, 2017 at 12:47:30AM -0700, Richard Henderson wrote: >> On 04/16/2017 04:23 PM, Stafford Horne wrote: >>> When debugging in gdb you might want to inspect instructions in mapped >>> pages or in exception vectors like 0x800 etc. This was previously not >>> possible in qemu since the *get_phys_page_debug() routine only looked >>> into the data tlb. >>> >>> Change to fall back to look into instruction tlb and plain physical >>> pages. >>> >>> Signed-off-by: Stafford Horne <shorne@gmail.com> >> >> Oh the horrors of a software managed TLB. >> >> You might do well to architecturally define an SPR that holds the page table >> base, even if for real hardware that's only used by the software refill to >> load up the address. >> >> That would give qemu the option of performing a real page table walk. This >> would fix this debug hook properly (so that you can examine pages that >> aren't in the TLB at all). It would also optionally allow QEMU to skip the >> software refill, which *significantly* speeds up emulation. > > Understood, I guess we would also need a way to represent which paging > model we are using (1 level, 2 level etc)? I suppose. You really have a 1-level lookup? For huge pages only, or is this a virtual 2-level lookup with double-faulting to handle the second level? r~
On Tue, Apr 18, 2017 at 08:00:06AM -0700, Richard Henderson wrote: > On 04/18/2017 07:18 AM, Stafford Horne wrote: > > On Tue, Apr 18, 2017 at 12:47:30AM -0700, Richard Henderson wrote: > > > On 04/16/2017 04:23 PM, Stafford Horne wrote: > > > > When debugging in gdb you might want to inspect instructions in mapped > > > > pages or in exception vectors like 0x800 etc. This was previously not > > > > possible in qemu since the *get_phys_page_debug() routine only looked > > > > into the data tlb. > > > > > > > > Change to fall back to look into instruction tlb and plain physical > > > > pages. > > > > > > > > Signed-off-by: Stafford Horne <shorne@gmail.com> > > > > > > Oh the horrors of a software managed TLB. > > > > > > You might do well to architecturally define an SPR that holds the page table > > > base, even if for real hardware that's only used by the software refill to > > > load up the address. > > > > > > That would give qemu the option of performing a real page table walk. This > > > would fix this debug hook properly (so that you can examine pages that > > > aren't in the TLB at all). It would also optionally allow QEMU to skip the > > > software refill, which *significantly* speeds up emulation. > > > > Understood, I guess we would also need a way to represent which paging > > model we are using (1 level, 2 level etc)? > > I suppose. You really have a 1-level lookup? For huge pages only, or is > this a virtual 2-level lookup with double-faulting to handle the second > level? We don't, the linux kernel is implemented with basic 2-level lookup's with single fault. I was just thinking its not ideal for the emulator to assume the paging model since it could change from kernel to kernel. But I guess it will not change anytime soon. -Stafford
diff --git a/target/openrisc/mmu.c b/target/openrisc/mmu.c index 56b11d3..a6d7bcd 100644 --- a/target/openrisc/mmu.c +++ b/target/openrisc/mmu.c @@ -124,7 +124,7 @@ static int cpu_openrisc_get_phys_addr(OpenRISCCPU *cpu, { int ret = TLBRET_MATCH; - if (rw == 2) { /* ITLB */ + if (rw == MMU_INST_FETCH) { /* ITLB */ *physical = 0; ret = cpu->env.tlb->cpu_openrisc_map_address_code(cpu, physical, prot, address, rw); @@ -221,12 +221,27 @@ hwaddr openrisc_cpu_get_phys_page_debug(CPUState *cs, vaddr addr) OpenRISCCPU *cpu = OPENRISC_CPU(cs); hwaddr phys_addr; int prot; + int miss; - if (cpu_openrisc_get_phys_addr(cpu, &phys_addr, &prot, addr, 0)) { - return -1; + /* Check memory for any kind of address, since during debug the + gdb can ask for anything, check data tlb for address */ + miss = cpu_openrisc_get_phys_addr(cpu, &phys_addr, &prot, addr, 0); + + /* Check instruction tlb */ + if (miss) { + miss = cpu_openrisc_get_phys_addr(cpu, &phys_addr, &prot, addr, MMU_INST_FETCH); + } + + /* Last, fall back to a plain address */ + if (miss) { + miss = cpu_openrisc_get_phys_nommu(cpu, &phys_addr, &prot, addr, 0); } - return phys_addr; + if (miss) { + return -1; + } else { + return phys_addr; + } } void cpu_openrisc_mmu_init(OpenRISCCPU *cpu)
When debugging in gdb you might want to inspect instructions in mapped pages or in exception vectors like 0x800 etc. This was previously not possible in qemu since the *get_phys_page_debug() routine only looked into the data tlb. Change to fall back to look into instruction tlb and plain physical pages. Signed-off-by: Stafford Horne <shorne@gmail.com> --- target/openrisc/mmu.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-)