[PATCH v3 4/6] KVM: PPC: Book3s HV: Hold LPIDs in an unsigned long

Jordan Niethe jniethe5 at gmail.com
Wed Aug 16 13:19:17 AEST 2023

On 14/8/23 6:15 pm, David Laight wrote:
> From: Jordan Niethe
>> Sent: 07 August 2023 02:46
>> The LPID register is 32 bits long. The host keeps the lpids for each
>> guest in an unsigned word struct kvm_arch. Currently, LPIDs are already
>> limited by mmu_lpid_bits and KVM_MAX_NESTED_GUESTS_SHIFT.
>> The nestedv2 API returns a 64 bit "Guest ID" to be used be the L1 host
>> for each L2 guest. This value is used as an lpid, e.g. it is the
>> parameter used by H_RPT_INVALIDATE. To minimize needless special casing
>> it makes sense to keep this "Guest ID" in struct kvm_arch::lpid.
>> This means that struct kvm_arch::lpid is too small so prepare for this
>> and make it an unsigned long. This is not a problem for the KVM-HV and
>> nestedv1 cases as their lpid values are already limited to valid ranges
>> so in those contexts the lpid can be used as an unsigned word safely as
>> needed.
> Shouldn't it be changed to u64?

This will only be for 64-bit PPC so an unsigned long will always be 64 
bits wide, but I can use a u64 instead.

> 	David
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)

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