Re: [PATCH 2/6] KVM: PPC: Book3S HV: Update LPID allocator init for POWER9, Nested

[Fabiano Rosas <farosas@linux.ibm.com>]

Nicholas Piggin <npiggin@gmail.com> writes:

> The LPID allocator init is changed to:
> - use mmu_lpid_bits rather than hard-coding;
> - use KVM_MAX_NESTED_GUESTS for nested hypervisors;
> - not reserve the top LPID on POWER9 and newer CPUs.
>
> The reserved LPID is made a POWER7/8-specific detail.
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---

Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>

>  arch/powerpc/include/asm/kvm_book3s_asm.h |  2 +-
>  arch/powerpc/include/asm/reg.h            |  2 --
>  arch/powerpc/kvm/book3s_64_mmu_hv.c       | 29 ++++++++++++++++-------
>  arch/powerpc/kvm/book3s_hv_rmhandlers.S   |  8 +++++++
>  arch/powerpc/mm/init_64.c                 |  3 +++
>  5 files changed, 33 insertions(+), 11 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_book3s_asm.h b/arch/powerpc/include/asm/kvm_book3s_asm.h
> index b6d31bff5209..e6bda70b1d93 100644
> --- a/arch/powerpc/include/asm/kvm_book3s_asm.h
> +++ b/arch/powerpc/include/asm/kvm_book3s_asm.h
> @@ -15,7 +15,7 @@
>  #define XICS_IPI		2	/* interrupt source # for IPIs */
>
>  /* LPIDs we support with this build -- runtime limit may be lower */
> -#define KVMPPC_NR_LPIDS			(LPID_RSVD + 1)
> +#define KVMPPC_NR_LPIDS			(1UL << 12)
>
>  /* Maximum number of threads per physical core */
>  #define MAX_SMT_THREADS		8
> diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
> index 1e14324c5190..1e8b2e04e626 100644
> --- a/arch/powerpc/include/asm/reg.h
> +++ b/arch/powerpc/include/asm/reg.h
> @@ -473,8 +473,6 @@
>  #ifndef SPRN_LPID
>  #define SPRN_LPID	0x13F	/* Logical Partition Identifier */
>  #endif
> -#define   LPID_RSVD_POWER7	0x3ff	/* Reserved LPID for partn switching */
> -#define   LPID_RSVD		0xfff	/* Reserved LPID for partn switching */
>  #define	SPRN_HMER	0x150	/* Hypervisor maintenance exception reg */
>  #define   HMER_DEBUG_TRIG	(1ul << (63 - 17)) /* Debug trigger */
>  #define	SPRN_HMEER	0x151	/* Hyp maintenance exception enable reg */
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> index 09fc52b6f390..5be92d5bc099 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> @@ -256,7 +256,7 @@ void kvmppc_map_vrma(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot,
>
>  int kvmppc_mmu_hv_init(void)
>  {
> -	unsigned long rsvd_lpid;
> +	unsigned long nr_lpids;
>
>  	if (!mmu_has_feature(MMU_FTR_LOCKLESS_TLBIE))
>  		return -EINVAL;
> @@ -264,16 +264,29 @@ int kvmppc_mmu_hv_init(void)
>  	if (cpu_has_feature(CPU_FTR_HVMODE)) {
>  		if (WARN_ON(mfspr(SPRN_LPID) != 0))
>  			return -EINVAL;
> +		nr_lpids = 1UL << mmu_lpid_bits;
> +	} else {
> +		nr_lpids = KVM_MAX_NESTED_GUESTS;
>  	}
>
> -	/* POWER8 and above have 12-bit LPIDs (10-bit in POWER7) */
> -	if (cpu_has_feature(CPU_FTR_ARCH_207S))
> -		rsvd_lpid = LPID_RSVD;
> -	else
> -		rsvd_lpid = LPID_RSVD_POWER7;
> +	if (nr_lpids > KVMPPC_NR_LPIDS)
> +		nr_lpids = KVMPPC_NR_LPIDS;
> +
> +	if (!cpu_has_feature(CPU_FTR_ARCH_300)) {
> +		/* POWER7 has 10-bit LPIDs, POWER8 has 12-bit LPIDs */
> +		if (cpu_has_feature(CPU_FTR_ARCH_207S))
> +			WARN_ON(nr_lpids != 1UL << 12);
> +		else
> +			WARN_ON(nr_lpids != 1UL << 10);
> +
> +		/*
> +		 * Reserve the last implemented LPID use in partition
> +		 * switching for POWER7 and POWER8.
> +		 */
> +		nr_lpids -= 1;
> +	}
>
> -	/* rsvd_lpid is reserved for use in partition switching */
> -	kvmppc_init_lpid(rsvd_lpid);
> +	kvmppc_init_lpid(nr_lpids);
>
>  	return 0;
>  }
> diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> index d185dee26026..0c552885a032 100644
> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> @@ -50,6 +50,14 @@
>  #define STACK_SLOT_UAMOR	(SFS-88)
>  #define STACK_SLOT_FSCR		(SFS-96)
>
> +/*
> + * Use the last LPID (all implemented LPID bits = 1) for partition switching.
> + * This is reserved in the LPID allocator. POWER7 only implements 0x3ff, but
> + * we write 0xfff into the LPID SPR anyway, which seems to work and just
> + * ignores the top bits.
> + */
> +#define   LPID_RSVD		0xfff
> +
>  /*
>   * Call kvmppc_hv_entry in real mode.
>   * Must be called with interrupts hard-disabled.
> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
> index 35f46bf54281..ad1a41e3ff1c 100644
> --- a/arch/powerpc/mm/init_64.c
> +++ b/arch/powerpc/mm/init_64.c
> @@ -371,6 +371,9 @@ void register_page_bootmem_memmap(unsigned long section_nr,
>
>  #ifdef CONFIG_PPC_BOOK3S_64
>  unsigned int mmu_lpid_bits;
> +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> +EXPORT_SYMBOL_GPL(mmu_lpid_bits);
> +#endif
>  unsigned int mmu_pid_bits;
>
>  static bool disable_radix = !IS_ENABLED(CONFIG_PPC_RADIX_MMU_DEFAULT);