On Thu, Jun 29, 2017 at 02:59:39PM +1000, Suraj Jitindar Singh wrote:
> The Processor Compatibility Register (PCR) I used to set the
> compatibility mode of the processor using the SET_ONE_REG ioctl on
> KVM_REG_PPC_ARCH_COMPAT. Previously this was only called when a compat
> mode was actually in use, however a recent patch made it unconditional.
> Calling this in KVM_PR fails as there is no handler for that call and it
> is thus impossible to start a machine with KVM_PR.
>
> Change ppc_set_compat() so that the ioctl is only actually called if a
> compat mode is in use. This means that a KVM_PR guest can boot.
> Additionally the current behaviour for KVM_HV is preserved where a compat
> mode of 0 set pcr and arch_compat in the vcore struct to zero, both of
> which are initialised to zero anyway.
>
> Fixes: 37f516defa2e ("pseries: Reset CPU compatibility mode")
>
> Signed-off-by: Suraj Jitindar Singh <sjitindarsi...@gmail.com>
This doesn't seem quite right. With this change, how would we ever
turn compatibility mode _off_ (which could happen on reset if nothing
else). Really we should add this pseudo-register to KVM PR, although
I'm fine with also having a qemu workaround to let it work with older
PR versions.
>
> ---
>
> Based on: dwg/ppc-for-2.10
>
> target/ppc/compat.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target/ppc/compat.c b/target/ppc/compat.c
> index f1b67fa..4482206 100644
> --- a/target/ppc/compat.c
> +++ b/target/ppc/compat.c
> @@ -143,7 +143,7 @@ void ppc_set_compat(PowerPCCPU *cpu, uint32_t compat_pvr,
> Error **errp)
> cpu->compat_pvr = compat_pvr;
> env->spr[SPR_PCR] = pcr & pcc->pcr_mask;
>
> - if (kvm_enabled()) {
> + if (kvm_enabled() && compat_pvr) {
> int ret = kvmppc_set_compat(cpu, cpu->compat_pvr);
> if (ret < 0) {
> error_setg_errno(errp, -ret,
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
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