Re: arm64 mrs and system registers
Paul Floyd <[email protected]>
| Newsgroups | gmane.os.freebsd.devel.arm |
|---|---|
| Message-ID | <[email protected]> |
> On 8 Apr 2024, at 22:31, Warner Losh <[email protected]> wrote: > > > > On Mon, Apr 8, 2024 at 9:03 PM Paul Floyd <[email protected] <mailto:[email protected]>> wrote: >> Hi >> >> I've been looking at this bugzilla item >> >> https://bugs.kde.org/show_bug.cgi?id=392146 >> >> Is there any difference between Linux and FreeBSD when it comes to what >> registers and fields are exposed by the kernel (see comment 17 in the >> link above). > > I don't think so. We've not seen issues with other drivers on aarch64 except > when they were written on x86 and didn't have the synchronization needed > for the weaker memory models in aarch64 systems. > >> I did have a poke around the kernel code but it's a bit hard to tell >> exactly which of the access macros are being used, without exhaustively >> grepping for them one by one. > > Yea, I think that there's missing atomics on the state transitions and/or > some missing locking that "magically" provides barriers that make it work > on x86. > Hi There aren’t any memory issues. The problem is that the opcodes aren’t fully covered. There are 3 aspects to that 1. What the kernel exposes 2. What Valgrind implements (usually a subset of point 1 but it should claim things that the kernel doesn’t support). 3. Actually handling the opcode. If Linux and FreeBSD expose the same things then I can go ahead with looking at a common solution. A+ Paul