Re: [Qemu-ppc] [RFC PATCH 05/17] KVM: PPC: booke: Extend MAS2 EPN mask for 64-bit

[Caraman Mihai Claudiu-B02008]

> -----Original Message-----
> From: Alexander Graf [mailto:address@hidden
> Sent: Wednesday, July 04, 2012 4:50 PM
> To: Caraman Mihai Claudiu-B02008
> Cc: address@hidden; address@hidden; linuxppc-
> address@hidden; address@hidden
> Subject: Re: [Qemu-ppc] [RFC PATCH 05/17] KVM: PPC: booke: Extend MAS2
> EPN mask for 64-bit
> 
> 
> On 25.06.2012, at 14:26, Mihai Caraman wrote:
> 
> > Extend MAS2 EPN mask for 64-bit hosts, to retain most significant bits.
> > Change get tlb eaddr to use this mask.
> 
> Please see section 6.11.4.8 in the PowerISA 2.06b:
> 
> MMU behavior is largely unaffected by whether the thread is in 32-bit
> computation mode (MSRCM=0) or 64- bit computation mode (MSRCM=1). The
> only differ- ences occur in the EPN field of the TLB entry and the EPN
> field of MAS2. The differences are summarized here.
> 
>       *  Executing a tlbwe instruction in 32-bit mode will set bits 0:31
> of the TLB EPN field to zero unless MAS0ATSEL is set, in which case those
> bits are not written to zero.
>       *  In 32-bit implementations, MAS2U can be used to read or write
> EPN0:31 of MAS2.
> 
> So if MSR.CM is not set tlbwe should mask the upper 32 bits out - which
> can happen regardless of CONFIG_64BIT.

MAS2_EPN reflects EPN field of MAS2 aka bits 0:51 (for MAV = 1.0) according
to section 6.10.3.10 in the PowerISA 2.06b.

MAS2_EPN is not used in tlbwe execution emulation, we have MAS2_VAL define
for this case.

> Also, we need to implement MAS2U, to potentially make the upper 32bits of
> MAS2 available, right? But that one isn't as important as the first bit.

MAS2U is guest privileged why does it need special care?

Freescale core Manuals and EREF does not mention MAS2U so I think I our case
it is not implemented.

-Mike