On Mon, 2016-10-31 at 16:44 +1100, Paul Mackerras wrote:
> On Mon, Oct 31, 2016 at 11:28:23AM +1100, Suraj Jitindar Singh wrote:
> >
> > The function kvmppc_set_arch_compat() is used to determine the
> > value of the
> > processor compatibility register (PCR) for a guest running in a
> > given
> > compatibility mode. There is currently no support for v3.00 of the
> > ISA.
> >
> > Add support for v3.00 of the ISA which adds an ISA v2.07
> > compatilibity mode
> > to the PCR.
> >
> > We also add a check to ensure the processor we are running on is
> > capable of
> > emulating the chosen processor (for example a POWER7 cannot emulate
> > a
> > POWER8, similarly with a POWER8 and a POWER9).
> >
> > Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
> > ---
> > arch/powerpc/kvm/book3s_hv.c | 32 +++++++++++++++++++++++---------
> > 1 file changed, 23 insertions(+), 9 deletions(-)
> >
> > diff --git a/arch/powerpc/kvm/book3s_hv.c
> > b/arch/powerpc/kvm/book3s_hv.c
> > index 3686471..24681e7 100644
> > --- a/arch/powerpc/kvm/book3s_hv.c
> > +++ b/arch/powerpc/kvm/book3s_hv.c
> > @@ -311,24 +311,38 @@ static int kvmppc_set_arch_compat(struct
> > kvm_vcpu *vcpu, u32 arch_compat)
> > * If an arch bit is set in PCR, all the
> > defined
> > * higher-order arch bits also have to be
> > set.
> > */
> > - pcr = PCR_ARCH_206 | PCR_ARCH_205;
> > + if (cpu_has_feature(CPU_FTR_ARCH_206))
> > + pcr |= PCR_ARCH_205;
> > + if (cpu_has_feature(CPU_FTR_ARCH_207S))
> > + pcr |= PCR_ARCH_206;
> > + if (cpu_has_feature(CPU_FTR_ARCH_300))
> > + pcr |= PCR_ARCH_207;
> > break;
> > case PVR_ARCH_206:
> > case PVR_ARCH_206p:
> > - pcr = PCR_ARCH_206;
> > + /* Must be at least v2.06 to (emulate) it
> > */
> > + if (!cpu_has_feature(CPU_FTR_ARCH_206))
> > + return -EINVAL;
> > + if (cpu_has_feature(CPU_FTR_ARCH_207S))
> > + pcr |= PCR_ARCH_206;
> > + if (cpu_has_feature(CPU_FTR_ARCH_300))
> > + pcr |= PCR_ARCH_207;
> > break;
> > case PVR_ARCH_207:
> > + /* Must be at least v2.07 to (emulate) it
> > */
> > + if (!cpu_has_feature(CPU_FTR_ARCH_207S))
> > + return -EINVAL;
> > + if (cpu_has_feature(CPU_FTR_ARCH_300))
> > + pcr |= PCR_ARCH_207;
> > + break;
> > + case PVR_ARCH_300:
> > + /* Must be at least v3.00 to (emulate) it
> > */
> > + if (!cpu_has_feature(CPU_FTR_ARCH_300))
> > + return -EINVAL;
> > break;
> I can't help thinking that the repetitive structure of the lines
> you're adding must imply a regularity that could be expressed more
> concisely. If you defined a dummy PCR_ARCH_300 bit as 0x10, perhaps
> you could do something like this:
>
> if (cpu_has_feature(CPU_FTR_ARCH_300))
> host_pcr_bit = PCR_ARCH_300;
> else if (cpu_has_feature(CPU_FTR_ARCH_207S))
> host_pcr_bit = PCR_ARCH_207;
> else
else if
> host_pcr_bit = PCR_ARCH_206;
else
host_pcr_bit = PCR_ARCH_205;
>
> switch (arch_compat) {
> case PVR_ARCH_205:
> guest_pcr_bit = PCR_ARCH_205;
> break;
> case PVR_ARCH_206:
> guest_pcr_bit = PCR_ARCH_206;
> break;
> case PVR_ARCH_207:
> case PVR_ARCH_207S:
> guest_pcr_bit = PCR_ARCH_207;
> break;
> case PVR_ARCH_300:
> guest_pcr_bit = PCR_ARCH_300;
> break;
> default:
> return -EINVAL;
> }
>
> if (guest_pcr_bit > host_pcr_bit)
> return -EINVAL;
>
> pcr = host_pcr_bit - guest_pcr_bit;
That approach is simpler and more extensible, I guess I don't really
like that it relies on the assumption that the PCR bits remain
consecutive and breaks if that assumption becomes invalid, which may
never be the case. I guess we can assume they will be for now and fix
it in the event that ever changes.
>
> The translation from arch_compat to guest_pcr_bit might look neater
> as
> a table lookup on the low bits of arch_compat, after a bounds check.
Is that really necessary? I don't see the benefit and the code is more
readable in it's current form IMO.
Something like this?
unsigned long guest_pcr_bits = {0, /* 0 */
0, /* 1 */
PCR_ARCH_205, /* 0x0F000002 */
PCR_ARCH_206, /* 0x0F000003 */
PCR_ARCH_207, /* 0x0F000004 */
PCR_ARCH_300 }; /* 0x0F000005 */
if (arch_compat <= PVR_ARCH_300 && arch_compat >= PVR_ARCH_205)
guest_pcr_bit = guest_pcr_bits[arch_compat & 0xF];
else
return -EINVAL;
>
> Paul.
--
To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
