Date: Wed, 29 Jan 2014 21:51:56 -0600 From: Stacey Son <sson@freebsd.org> To: Adrian Chadd <adrian@freebsd.org> Cc: "freebsd-mips@freebsd.org" <freebsd-mips@freebsd.org> Subject: Re: More trapframe panics Message-ID: <B431B251-9221-4E76-A1FC-2D0974C12BBE@freebsd.org> In-Reply-To: <CAJ-Vmo=RB8cequSK=9UrU6A6v-9KU3u-wQZY5n-5keAhBYu9=Q@mail.gmail.com> References: <52E42A1B.3040907@rewt.org.uk> <CACVs6=--Qy_8poWdHdCXYKqkO22=dvHhW8=Uma8kLR%2BhCoZDxw@mail.gmail.com> <CA%2B7sy7ATMTjdWD5%2BNYCJPb=AWmeJoUwbgRdf=%2Bb4uYsJO0UUfw@mail.gmail.com> <CACVs6=8ie2x16c4bafG4zaJS4UV%2BXT1ooJkm%2BdwT5%2BdSS%2B-p0Q@mail.gmail.com> <CA%2B7sy7BEgvMNJKiR4bSSGZ_BE1T5W3Hujq8_2C6JjPC1bFwO6A@mail.gmail.com> <6354182D-B1D3-4B2E-BEEC-37A2A725A099@bsdimp.com> <52E67F45.20402@rewt.org.uk> <2912AEFA-AA0C-456A-A814-363478BFC900@bsdimp.com> <CAJ-VmokDYS6CBAJp_G=4yKeb4O6yOXVmx%2B8Mshzx5RCBjM4VwA@mail.gmail.com> <52E781C6.2050308@rewt.org.uk> <DBAE1C04-F150-4EAE-8134-014F065E4058@FreeBSD.org> <CAJ-Vmo=RB8cequSK=9UrU6A6v-9KU3u-wQZY5n-5keAhBYu9=Q@mail.gmail.com>
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On Jan 29, 2014, at 4:29 PM, Adrian Chadd <adrian@freebsd.org> wrote: > isn't there a way to probe the valid pagemask values? >=20 > I thought I read some way of writing in pagemask values into a fixed > TLB entry and then reading them back to see which bit(s) are set and > cleared. >=20 > That way we could maybe do the above at boot-time with minimal = evilness. Yes, see page 107 of http://www.t-es-t.hu/download/mips/md00090c.pdf "Software may determine which page sizes are supported by writing all = ones to the PageMask register, then reading the value back. If a pair of = bits reads back as ones, the processor implements that page size. The = operation of the pro- cessor is UNDEFINED if software loads the Mask = field with a value other than one of those listed in Table 9.16, even if = the hardware returns a different value on read. Hardware may depend on = this requirement in implementing hard- ware structures" -stacey.=
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