[PATCH] New MMU feature for new hpte format in ISA3

[Aneesh Kumar K.V]

Balbir Singh <bsingharora at gmail.com> writes:

> This patch has been lightly tested and needs testing
> on additional platforms and different page sizes, largely
> due to the mmu_features changes noted below
>
> Commit 50de596de introduced support for the new PTE
> format in the functions hpte_encode_r and hpte_encode_avpn.
> This patch abstracts the change under
> MMU_FTR_ISA3_HPTE_FORMAT. This bit is provided by the
> ibm,pa-feature mechanism; hypervisor for guests
> and via firmware for powernv.


IIUC, ISA 3.0 require new hpte format. So not sure why would need a mmu
feature bit for it. For a guest running in P8 compat mode, which is
negotiated via ibm,client-architecture-support , the HCALL interface
should do the necessary mapping from the HPTE format we use with p8
kernel to the new ISA 3.0 format.

>
> The patch has a larger impact as the new feature bit
> changes the definition of mmu_features from unsigned int
> to unsigned long and also changes the print in setup_64.c
> of the same feature.
>
> This patch needs complementary changes to the
> ibm,client-architecture in arch/powerpc/kernel/prom_init.c.
> This is noted as a TODO
>
> Cc: Paul Mackerras <paulus at samba.org>
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Cc: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
>
> Signed-off-by: Balbir Singh <bsingharora at gmail.com>
> ---
>  arch/powerpc/include/asm/book3s/64/mmu-hash.h |  5 ++---
>  arch/powerpc/include/asm/cputable.h           |  2 +-
>  arch/powerpc/include/asm/mmu.h                | 11 ++++++++++-
>  arch/powerpc/kernel/prom.c                    |  1 +
>  arch/powerpc/kernel/setup_64.c                |  2 +-
>  5 files changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/mmu-hash.h b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> index 290157e..373f765 100644
> --- a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> +++ b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> @@ -229,7 +229,7 @@ static inline unsigned long hpte_encode_avpn(unsigned long vpn, int psize,
>  	 */
>  	v = (vpn >> (23 - VPN_SHIFT)) & ~(mmu_psize_defs[psize].avpnm);
>  	v <<= HPTE_V_AVPN_SHIFT;
> -	if (!cpu_has_feature(CPU_FTR_ARCH_300))
> +	if (!mmu_has_feature(MMU_FTR_ISA3_HPTE_FORMAT))
>  		v |= ((unsigned long) ssize) << HPTE_V_SSIZE_SHIFT;
>  	return v;
>  }
> @@ -256,8 +256,7 @@ static inline unsigned long hpte_encode_v(unsigned long vpn, int base_psize,
>  static inline unsigned long hpte_encode_r(unsigned long pa, int base_psize,
>  					  int actual_psize, int ssize)
>  {
> -
> -	if (cpu_has_feature(CPU_FTR_ARCH_300))
> +	if (mmu_has_feature(MMU_FTR_ISA3_HPTE_FORMAT))
>  		pa |= ((unsigned long) ssize) << HPTE_R_3_0_SSIZE_SHIFT;
>
>  	/* A 4K page needs no special encoding */
> diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
> index df4fb5f..469c9be 100644
> --- a/arch/powerpc/include/asm/cputable.h
> +++ b/arch/powerpc/include/asm/cputable.h
> @@ -58,7 +58,7 @@ struct cpu_spec {
>  	unsigned long	cpu_features;		/* Kernel features */
>  	unsigned int	cpu_user_features;	/* Userland features */
>  	unsigned int	cpu_user_features2;	/* Userland features v2 */
> -	unsigned int	mmu_features;		/* MMU features */
> +	unsigned long	mmu_features;		/* MMU features */
>
>  	/* cache line sizes */
>  	unsigned int	icache_bsize;
> diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
> index e53ebeb..e121db1 100644
> --- a/arch/powerpc/include/asm/mmu.h
> +++ b/arch/powerpc/include/asm/mmu.h
> @@ -92,6 +92,12 @@
>   * Radix page table available
>   */
>  #define MMU_FTR_RADIX			ASM_CONST(0x80000000)
> +/*
> + * Support of new PTE format as defined in ISA 3.0
> + */
> +#ifdef CONFIG_PPC_STD_MMU_64
> +#define MMU_FTR_ISA3_HPTE_FORMAT	ASM_CONST(0x100000000)
> +#endif
>
>  /* MMU feature bit sets for various CPUs */
>  #define MMU_FTRS_DEFAULT_HPTE_ARCH_V2	\
> @@ -128,10 +134,13 @@ enum {
>  #ifdef CONFIG_PPC_RADIX_MMU
>  		MMU_FTR_RADIX |
>  #endif
> +#ifdef CONFIG_PPC_STD_MMU_64
> +		MMU_FTR_ISA3_HPTE_FORMAT |
> +#endif
>  		0,
>  };
>
> -static inline int mmu_has_feature(unsigned long feature)
> +static inline unsigned long mmu_has_feature(unsigned long feature)
>  {
>  	return (MMU_FTRS_POSSIBLE & cur_cpu_spec->mmu_features & feature);
>  }
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index 946e34f..f9cb4a9 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -169,6 +169,7 @@ static struct ibm_pa_feature {
>  	{CPU_FTR_TM_COMP, 0, 0,
>  	 PPC_FEATURE2_HTM_COMP|PPC_FEATURE2_HTM_NOSC_COMP, 22, 0, 0},
>  	{0, MMU_FTR_RADIX, 0, 0,		40, 0, 0},
> +	{0, MMU_FTR_ISA3_HPTE_FORMAT, 0, 0,	58, 0, 0},


IIUC, that bit indicate the usage of segment table. Not really new HPTE
format. With ISA 3.0, hash mode always need the new hpte format. Hence it
is not a something we could disable. ie, if we are on ISA 3.0 and using
hash mode, hash page table entries should have new format.


>  };
>
>  static void __init scan_features(unsigned long node, const unsigned char *ftrs,
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index 96d4a2b..2e15490 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -561,7 +561,7 @@ void __init setup_system(void)
>  	pr_info("  always          = 0x%016lx\n", CPU_FTRS_ALWAYS);
>  	pr_info("cpu_user_features = 0x%08x 0x%08x\n", cur_cpu_spec->cpu_user_features,
>  		cur_cpu_spec->cpu_user_features2);
> -	pr_info("mmu_features      = 0x%08x\n", cur_cpu_spec->mmu_features);
> +	pr_info("mmu_features      = 0x%016lx\n", cur_cpu_spec->mmu_features);
>  	pr_info("firmware_features = 0x%016lx\n", powerpc_firmware_features);
>
>  #ifdef CONFIG_PPC_STD_MMU_64
> -- 
> 2.5.5

-aneesh