On Wed, Mar 11, 2020 at 06:45:06PM +0100, Maxime Villard wrote:
> Please CC me for issues related to NVMM, there is a number of lists where
> I'm not subscribed.
>
> My understanding is that this commit is the cause (CC ad@):
>
> https://mail-index.netbsd.org/source-changes/2019/12/06/msg111617.html
>
> NVMM reschedules the thread when the SPCF_SHOULDYIELD flag is set. But
> after this change the flag never gets set, so the rescheduling never
> occurs, and NVMM is stuck with running the guest forever unless a signal
> is caught in the emulator thread.
>
> The test program below shows the difference. On NetBSD-9 you have many
> "resched", as expected. On NetBSD-current you have none.
>
> Andrew, can you have a look? There is a good dozen of places that use
> SPCF_SHOULDYIELD for reschedulings, and they too may potentially be buggy
> now.
Yes that was incorrect and I have fixed it. I will see about adding a
wrapper function for this too.
Andrew
>
> Thanks,
> Maxime
>
>
>
> ---------------------------------------------------------------------------
>
> /*
> * # gcc -o test test.c -lnvmm
> * # ./test
> */
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <unistd.h>
> #include <sys/mman.h>
> #include <fcntl.h>
> #include <nvmm.h>
> #include <stdint.h>
> #include <string.h>
>
> int main()
> {
> uint8_t instr[] = { 0xEB, 0xFE };
> struct nvmm_machine mach;
> struct nvmm_vcpu vcpu;
> uintptr_t hva;
>
> nvmm_init();
> nvmm_machine_create(&mach);
> nvmm_vcpu_create(&mach, 0, &vcpu);
>
> hva = (uintptr_t)mmap(NULL, 4096, PROT_READ|PROT_WRITE,
> MAP_ANON|MAP_PRIVATE, -1, 0);
> nvmm_hva_map(&mach, hva, 4096);
> nvmm_gpa_map(&mach, hva, 0xFFFF0000, 4096, PROT_READ|PROT_EXEC);
>
> memcpy((void *)hva, instr, sizeof(instr));
>
> nvmm_vcpu_getstate(&mach, &vcpu, NVMM_X64_STATE_GPRS);
> vcpu.state->gprs[NVMM_X64_GPR_RIP] = 0;
> nvmm_vcpu_setstate(&mach, &vcpu, NVMM_X64_STATE_GPRS);
>
> while (1) {
> printf("looping\n");
> nvmm_vcpu_run(&mach, &vcpu);
>
> switch (vcpu.exit->reason) {
> case NVMM_VCPU_EXIT_NONE:
> printf("resched\n");
> break;
> default:
> printf("unknown: %d\n", vcpu.exit->reason);
> break;
> }
> }
> }
