Does someone knows how it will work?

  1. Some wine/proton wizardry
  2. Gaming VM with GPU passthrough
  • Domi@lemmy.secnd.me
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    16 hours ago

    According to their now deleted Reddit account, it will use a custom Proton build on Intel and Zen 4 CPUs. For every other CPU you will need a kernel module.

    • Mttw_@lemmy.dbzer0.com
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      10 hours ago

      Correction: usermode is only supported by zen4 (or newer) and intel Ivy Bridge (or newer).

      The reason is pretty simple: only from those generations onwards a new instruction was added (cpuid faulting) which is executed in the hardware itself, old generations simply lacks the silicon for it.

      cpu faulting is used to trap usermode cpuid calls and can be used to return spoofed values, without needing an hypervisor.

      • mecen@lemmy.caOP
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        11 hours ago

        If ivy bridge then from 3 gen which means pretty much any Intel made from 2012.

        But for AMD from 7000 series which means CPU from 2022.

        It sucks to be AMD user.

        • Mttw_@lemmy.dbzer0.com
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          10 hours ago

          yeah, more on that: linux kernel has support for cpuid faulting for supported intel cpus since 2017, while amd since only last year. Not sure why amd was slower on this.

      • kkj@lemmy.dbzer0.com
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        10 hours ago

        I wonder if the new 5800X3D will support it. I’d give it maybe a 1% chance. I doubt they changed all that much. Sure would be nice for people on AM4, though.

        • Mttw_@lemmy.dbzer0.com
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          9 hours ago

          No, 5800x3d is zen3 sadly.

          But you can actually test it with a small python script:

          # docs: https://man.archlinux.org/man/arch_prctl.2
          import ctypes
          import errno
          import mmap
          import os
          import signal
          import subprocess
          import sys
          
          SYS_arch_prctl = 158
          ARCH_SET_CPUID = 0x1012
          
          libc = ctypes.CDLL(None, use_errno=True)
          libc.syscall.restype = ctypes.c_long
          
          def arch_set_cpuid(enabled: bool) -> None:
              rc = libc.syscall(SYS_arch_prctl, ARCH_SET_CPUID, 1 if enabled else 0)
              if rc != 0:
                  e = ctypes.get_errno()
                  raise OSError(e, os.strerror(e))
          
          def make_cpuid_stub():
              # push rbx
              # xor eax, eax
              # cpuid
              # pop rbx
              # ret
              code = b"\x53\x31\xc0\x0f\xa2\x5b\xc3"
              mm = mmap.mmap(
                  -1,
                  len(code),
                  flags=mmap.MAP_PRIVATE | mmap.MAP_ANONYMOUS,
                  prot=mmap.PROT_READ | mmap.PROT_WRITE | mmap.PROT_EXEC,
              )
              mm.write(code)
              addr = ctypes.addressof(ctypes.c_char.from_buffer(mm))
              func = ctypes.CFUNCTYPE(None)(addr)
              func._mm = mm
              return func
          
          def child():
              cpuid = make_cpuid_stub()
          
              print("Trying normal CPUID...")
              cpuid()
              print("Normal CPUID worked.")
          
              try:
                  arch_set_cpuid(False)
              except OSError as e:
                  if e.errno == errno.ENODEV:
                      print("CPU does not support CPUID faulting.")
                      return 2
                  raise
          
              print("CPUID disabled for this thread. Calling CPUID again...")
              cpuid()  # should SIGSEGV -11 if faulting is supported
              print("Unexpected: CPUID did not fault.")
              return 0
          
          if __name__ == "__main__":
              if len(sys.argv) > 1 and sys.argv[1] == "child":
                  raise SystemExit(child())
          
              p = subprocess.run([sys.executable, __file__, "child"], text=True)
              print(f"child exit code: {p.returncode}")
          
              if p.returncode == -signal.SIGSEGV:
                  print("Result: CPUID faulting is supported and worked.")
              elif p.returncode == 2:
                  print("Result: CPUID faulting is not supported by the hardware.")
              else:
                  print("Result: test did not complete cleanly.")
          
          • kkj@lemmy.dbzer0.com
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            7 hours ago

            I was referring to AMD bringing the 5800X3D out of retirement. They said that they redesigned it. It’s probably just moving the cache under the CPU like on Zen5 3D, but I feel like there’s a very slight chance.

    • MalReynolds@slrpnk.net
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      15 hours ago

      you will need a kernel module.

      Yeah, Nah. That’s a nope, especially given it can be done in proton. Also, updated Denuvo in 3.2.1…

      Denuvo, just say no.

      • Mttw_@lemmy.dbzer0.com
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        10 hours ago

        No it cannot be done with proton alone. Proton/wine is only a translation layer: if a program makes cpuid calls, proton/wine cannot intercept them because cpuid is executed directly on hardware silicon.

    • mecen@lemmy.caOP
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      15 hours ago

      Kinda sucks for other architectures if only ryzen 7000 is supported

      Or if building proton for different architectures is feasible.