On Wed, 6 Jun 2018 10:53:17 +1000 David Gibson <da...@gibson.dropbear.id.au> wrote:
> On Tue, Jun 05, 2018 at 06:46:12PM +0200, Greg Kurz wrote: > > On Mon, 4 Jun 2018 10:53:22 +1000 > > David Gibson <da...@gibson.dropbear.id.au> wrote: > > > > > On Mon, May 07, 2018 at 01:52:42PM -0300, luporl wrote: > > > > According to PowerISA, the PIR register should be readable in privileged > > > > mode also, not only in hypervisor privileged mode. > > > > > > > > PowerISA 3.0 - 4.3.3 Processor Identification Register > > > > > > > > "Read access to the PIR is privileged; write access is not > > > > provided." > > > > > > Yes... but a little further down it says "The PIR is a hypervisor > > > resource". Looking at the older 2.07 ISA, it says that > > > guest-supervisor mode reads to the PIR should be redirected to the > > > GPIR register, which this change won't accomplish. > > > > > > > Hmmm, there are two definitions for the PIR, one in Book III-S (4.3.3) > > and one in Book III-E (5.3.3). It looks like you're referring to the > > latter... > > > > [Category:Embedded.Hypervisor] > > Read accesses to the PIR in guest supervisor state are > > mapped to the GPIR. > > > > The Book III-S definition doesn't mention the GPIR. > > Oops, sorry. Yes the GPIR stuff is only for BookE. The statement > about the PIR being a hypervisor resource is definitely in the BookS > section, however (both 2.07 and 3.0). > Yes it is, but IIUC, this means that the guest cannot modify it, eg, do mtspr. Section 4.4.4 in Book III-S has a list of SPRs that seem to indicate that mfspr doesn't require hypervisor state with the PIR. FWIW, this can be verified with xmon in a KVM guest: 0:mon> S ... srr0 = c0000000000cd06c srr1 = 8000000000001033 dsisr = 00000000 dscr = 0000000000000000 ppr = 0010000000000000 pir = 00000020 ... 0:mon> Sr 3ff SPR 0x3ff (1023) = 0x20 but with TCG xmon hits a program check: 0:mon> S ... srr0 = c0000000000ef204 srr1 = 8000000000041033 dsisr = 40000000 cpu 0x0: Vector: 700 (Program Check) at [c00000003ffdf510] ... cpu 0x0: Exception 700 (Program Check) in xmon, returning to main loop ... 0:mon> Sr 3ff SPR 0x3ff (1023) Faulted during read This patch makes xmon happy under TCG.
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