[PATCH v3 05/18] powerpc/85xx: Load all early TLB entries at once

Christophe Leroy christophe.leroy at csgroup.eu
Tue Oct 19 05:42:21 PDT 2021


Hi Scott,

Le 23/10/2015 à 05:54, Scott Wood a écrit :
> Use an AS=1 trampoline TLB entry to allow all normal TLB1 entries to
> be loaded at once.  This avoids the need to keep the translation that
> code is executing from in the same TLB entry in the final TLB
> configuration as during early boot, which in turn is helpful for
> relocatable kernels (e.g. kdump) where the kernel is not running from
> what would be the first TLB entry.
> 
> On e6500, we limit map_mem_in_cams() to the primary hwthread of a
> core (the boot cpu is always considered primary, as a kdump kernel
> can be entered on any cpu).  Each TLB only needs to be set up once,
> and when we do, we don't want another thread to be running when we
> create a temporary trampoline TLB1 entry.


Isn't that redundant with commit 78a235efdc42 ("powerpc/fsl_booke: set 
the tlb entry for the kernel address in AS1") ?

Should we revert commit 78a235efdc42 ?

Christophe

> 
> Signed-off-by: Scott Wood <scottwood at freescale.com>
> ---
> v3: Drop rename of settlbcam to preptlbcam, as the settlbcam wrapper
> was unused.
> 
>   arch/powerpc/kernel/setup_64.c   |  8 +++++
>   arch/powerpc/mm/fsl_booke_mmu.c  |  4 +--
>   arch/powerpc/mm/mmu_decl.h       |  1 +
>   arch/powerpc/mm/tlb_nohash.c     | 19 +++++++++++-
>   arch/powerpc/mm/tlb_nohash_low.S | 63 ++++++++++++++++++++++++++++++++++++++++
>   5 files changed, 92 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index bdcbb71..505ec2c 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -108,6 +108,14 @@ static void setup_tlb_core_data(void)
>   	for_each_possible_cpu(cpu) {
>   		int first = cpu_first_thread_sibling(cpu);
>   
> +		/*
> +		 * If we boot via kdump on a non-primary thread,
> +		 * make sure we point at the thread that actually
> +		 * set up this TLB.
> +		 */
> +		if (cpu_first_thread_sibling(boot_cpuid) == first)
> +			first = boot_cpuid;
> +
>   		paca[cpu].tcd_ptr = &paca[first].tcd;
>   
>   		/*
> diff --git a/arch/powerpc/mm/fsl_booke_mmu.c b/arch/powerpc/mm/fsl_booke_mmu.c
> index 354ba3c..bb1f88c 100644
> --- a/arch/powerpc/mm/fsl_booke_mmu.c
> +++ b/arch/powerpc/mm/fsl_booke_mmu.c
> @@ -141,8 +141,6 @@ static void settlbcam(int index, unsigned long virt, phys_addr_t phys,
>   	tlbcam_addrs[index].start = virt;
>   	tlbcam_addrs[index].limit = virt + size - 1;
>   	tlbcam_addrs[index].phys = phys;
> -
> -	loadcam_entry(index);
>   }
>   
>   unsigned long calc_cam_sz(unsigned long ram, unsigned long virt,
> @@ -188,6 +186,8 @@ static unsigned long map_mem_in_cams_addr(phys_addr_t phys, unsigned long virt,
>   		virt += cam_sz;
>   		phys += cam_sz;
>   	}
> +
> +	loadcam_multi(0, i, max_cam_idx);
>   	tlbcam_index = i;
>   
>   #ifdef CONFIG_PPC64
> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
> index 085b66b..27c3a2d 100644
> --- a/arch/powerpc/mm/mmu_decl.h
> +++ b/arch/powerpc/mm/mmu_decl.h
> @@ -152,6 +152,7 @@ extern int switch_to_as1(void);
>   extern void restore_to_as0(int esel, int offset, void *dt_ptr, int bootcpu);
>   #endif
>   extern void loadcam_entry(unsigned int index);
> +extern void loadcam_multi(int first_idx, int num, int tmp_idx);
>   
>   struct tlbcam {
>   	u32	MAS0;
> diff --git a/arch/powerpc/mm/tlb_nohash.c b/arch/powerpc/mm/tlb_nohash.c
> index 723a099..a7381fb 100644
> --- a/arch/powerpc/mm/tlb_nohash.c
> +++ b/arch/powerpc/mm/tlb_nohash.c
> @@ -42,6 +42,7 @@
>   #include <asm/tlbflush.h>
>   #include <asm/tlb.h>
>   #include <asm/code-patching.h>
> +#include <asm/cputhreads.h>
>   #include <asm/hugetlb.h>
>   #include <asm/paca.h>
>   
> @@ -628,10 +629,26 @@ static void early_init_this_mmu(void)
>   #ifdef CONFIG_PPC_FSL_BOOK3E
>   	if (mmu_has_feature(MMU_FTR_TYPE_FSL_E)) {
>   		unsigned int num_cams;
> +		int __maybe_unused cpu = smp_processor_id();
> +		bool map = true;
>   
>   		/* use a quarter of the TLBCAM for bolted linear map */
>   		num_cams = (mfspr(SPRN_TLB1CFG) & TLBnCFG_N_ENTRY) / 4;
> -		linear_map_top = map_mem_in_cams(linear_map_top, num_cams);
> +
> +		/*
> +		 * Only do the mapping once per core, or else the
> +		 * transient mapping would cause problems.
> +		 */
> +#ifdef CONFIG_SMP
> +		if (cpu != boot_cpuid &&
> +		    (cpu != cpu_first_thread_sibling(cpu) ||
> +		     cpu == cpu_first_thread_sibling(boot_cpuid)))
> +			map = false;
> +#endif
> +
> +		if (map)
> +			linear_map_top = map_mem_in_cams(linear_map_top,
> +							 num_cams);
>   	}
>   #endif
>   
> diff --git a/arch/powerpc/mm/tlb_nohash_low.S b/arch/powerpc/mm/tlb_nohash_low.S
> index 43ff3c7..68c4775 100644
> --- a/arch/powerpc/mm/tlb_nohash_low.S
> +++ b/arch/powerpc/mm/tlb_nohash_low.S
> @@ -400,6 +400,7 @@ _GLOBAL(set_context)
>    * extern void loadcam_entry(unsigned int index)
>    *
>    * Load TLBCAM[index] entry in to the L2 CAM MMU
> + * Must preserve r7, r8, r9, and r10
>    */
>   _GLOBAL(loadcam_entry)
>   	mflr	r5
> @@ -423,4 +424,66 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_BIG_PHYS)
>   	tlbwe
>   	isync
>   	blr
> +
> +/*
> + * Load multiple TLB entries at once, using an alternate-space
> + * trampoline so that we don't have to care about whether the same
> + * TLB entry maps us before and after.
> + *
> + * r3 = first entry to write
> + * r4 = number of entries to write
> + * r5 = temporary tlb entry
> + */
> +_GLOBAL(loadcam_multi)
> +	mflr	r8
> +
> +	/*
> +	 * Set up temporary TLB entry that is the same as what we're
> +	 * running from, but in AS=1.
> +	 */
> +	bl	1f
> +1:	mflr	r6
> +	tlbsx	0,r8
> +	mfspr	r6,SPRN_MAS1
> +	ori	r6,r6,MAS1_TS
> +	mtspr	SPRN_MAS1,r6
> +	mfspr	r6,SPRN_MAS0
> +	rlwimi	r6,r5,MAS0_ESEL_SHIFT,MAS0_ESEL_MASK
> +	mr	r7,r5
> +	mtspr	SPRN_MAS0,r6
> +	isync
> +	tlbwe
> +	isync
> +
> +	/* Switch to AS=1 */
> +	mfmsr	r6
> +	ori	r6,r6,MSR_IS|MSR_DS
> +	mtmsr	r6
> +	isync
> +
> +	mr	r9,r3
> +	add	r10,r3,r4
> +2:	bl	loadcam_entry
> +	addi	r9,r9,1
> +	cmpw	r9,r10
> +	mr	r3,r9
> +	blt	2b
> +
> +	/* Return to AS=0 and clear the temporary entry */
> +	mfmsr	r6
> +	rlwinm.	r6,r6,0,~(MSR_IS|MSR_DS)
> +	mtmsr	r6
> +	isync
> +
> +	li	r6,0
> +	mtspr	SPRN_MAS1,r6
> +	rlwinm	r6,r7,MAS0_ESEL_SHIFT,MAS0_ESEL_MASK
> +	oris	r6,r6,MAS0_TLBSEL(1)@h
> +	mtspr	SPRN_MAS0,r6
> +	isync
> +	tlbwe
> +	isync
> +
> +	mtlr	r8
> +	blr
>   #endif
> 



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