Date: Wed, 19 Feb 2014 11:49:55 -0800 From: Juli Mallett <jmallett@FreeBSD.org> To: Stacey Son <sson@freebsd.org> Cc: "freebsd-mips@freebsd.org" <freebsd-mips@freebsd.org> Subject: Re: [RFC] 16K page size for kernel thread stack (patch) Message-ID: <CACVs6=-y69-BN1s1LOU3NCZpq=B%2BTA_Oqd0spT9yxt7jdqOwFQ@mail.gmail.com> In-Reply-To: <DA9E475A-E278-4332-AAB7-2F82B4865E00@FreeBSD.org> References: <FAC31FA0-26B0-468E-826F-1A17ECA6DA65@FreeBSD.org> <CAJ-VmonLGOGChUohF7E3VBXFSohtAWPcADTxVo=8XreYosNu7A@mail.gmail.com> <EB4E2278-6E09-4495-8A0D-025A3AB4E4C7@freebsd.org> <CAJ-VmomH5SdJersWfeJSfUtTqu=HzjCSiw7E3hchaZAW-rujfA@mail.gmail.com> <DA9E475A-E278-4332-AAB7-2F82B4865E00@FreeBSD.org>
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On Wed, Feb 19, 2014 at 11:41 AM, Stacey Son <sson@freebsd.org> wrote: > > On Feb 18, 2014, at 7:58 PM, Adrian Chadd <adrian@freebsd.org> wrote: > > I don't think the mips24k/mips74k cores I have support ULRI. > > I am starting to wonder which mips CPUs actually do have an ULRI. > Basically-none. Some sources I've read from when the rdhwr approach was first implemented clearly thought it would pretty much never be implemented in hardware, and certainly most implementations after it became widespread didn't implement it, and its use only became common in the recent past. Until we started using it for TLS, GXemul would exit rather than trap on the rdhwr. I don't believe I've ever possessed a piece of hardware which actually implements the register itself, and there's actually a huge disincentive to do so because a lot of software has been written now which assumes that rdhwr will always trap and be implemented in software, and so won't set up the actual hardware register with the right value, breaking existing software. Juli.
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