On 06.11.2013, at 06:48, Paul Mackerras <pau...@samba.org> wrote: > On Mon, Sep 30, 2013 at 01:25:32PM +0200, Alexander Graf wrote: >> >> On 27.09.2013, at 10:06, Alexey Kardashevskiy wrote: >> >>> To be able to boot on newer hardware that the software support, >>> PowerISA defines a logical PVR, one per every PowerISA specification >>> version from 2.04. > [snip] >>> + case 205: >>> + spapr->arch_compat = CPU_POWERPC_LOGICAL_2_05; >>> + break; >>> + case 206: >>> + spapr->arch_compat = CPU_POWERPC_LOGICAL_2_06; >> >> Does it make sense to declare compat mode a number or would a string be >> easier for users? I can imagine that "-machine compat=power6" is easier to >> understand for a user than "-machine compat=205". > > That's probably true. I don't mind either way. > >> Also, we need to handle failure. If the kernel can not set the CPU to 2.05 >> mode for example (IIRC POWER8 doesn't allow you to) we should bail out here. > > POWER8 does have 2.05 (POWER6) and 2.06 (POWER7) compatibility modes. > >>> + /* Architecture compatibility mode */ >>> + uint32_t arch_compat; >> >> Do we really need to carry this in the vcpu struct? Or can we just >> fire-and-forget about it? If we want to preserve anything, it should be the >> PCR register. > > There are two relevant values here; the compatibility mode (if any) > that the user has requested via the command line, and the mode that > has been negotiated with the ibm,client-architecture-support (CAS) > call. CAS should select the latest mode supported by the guest that > is not later than the mode requested on the command line, and is > supported by QEMU, and is not later than the architecture of the > host. Both values should be sent across to the destination VM on > migration AFAICS.
So how does this work on pHyp? I thought the guest always comes up in full native compat mode and downgrades itself then? > On reset/reboot, the compatibility mode should not change. The device > tree that is supplied to the new SLOF instance should reflect the > current compatibility mode. Ok, this should work if we just don't touch PCR across reset. Alex
