Subject: Re: [PATCH 2/3] powperc/mm: read TLB Block Invalidate Characteristics

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Thu, 12 Sep 2019 20:14:15 +0530

Laurent Dufour <[email-masked]> writes:

> The PAPR document specifies the TLB Block Invalidate Characteristics which
> is telling which couple base page size / page size is supported by the
> H_BLOCK_REMOVE hcall.
>
> A new set of feature is added to the mmu_psize_def structure to record per
> base page size which page size is supported by H_BLOCK_REMOVE.
>
> A new init service is added to read the characteristics. The size of the
> buffer is set to twice the number of known page size, plus 10 bytes to
> ensure we have enough place.
>
> Signed-off-by: Laurent Dufour <[email-masked]>
> ---
>  arch/powerpc/include/asm/book3s/64/mmu.h |   3 +
>  arch/powerpc/platforms/pseries/lpar.c    | 107 +++++++++++++++++++++++
>  2 files changed, 110 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
> index 23b83d3593e2..675895dfe39f 100644
> --- a/arch/powerpc/include/asm/book3s/64/mmu.h
> +++ b/arch/powerpc/include/asm/book3s/64/mmu.h
> @@ -12,11 +12,14 @@
>   *    sllp  : is a bit mask with the value of SLB L || LP to be or'ed
>   *            directly to a slbmte "vsid" value
>   *    penc  : is the HPTE encoding mask for the "LP" field:
> + *    hblk  : H_BLOCK_REMOVE supported block size for this page size in
> + *            segment who's base page size is that page size.
>   *
>   */
>  struct mmu_psize_def {
>  	unsigned int	shift;	/* number of bits */
>  	int		penc[MMU_PAGE_COUNT];	/* HPTE encoding */
> +	int		hblk[MMU_PAGE_COUNT];	/* H_BLOCK_REMOVE support */
>  	unsigned int	tlbiel;	/* tlbiel supported for that page size */
>  	unsigned long	avpnm;	/* bits to mask out in AVPN in the HPTE */
>  	union {
> diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
> index 4f76e5f30c97..375e19b3cf53 100644
> --- a/arch/powerpc/platforms/pseries/lpar.c
> +++ b/arch/powerpc/platforms/pseries/lpar.c
> @@ -1311,6 +1311,113 @@ static void do_block_remove(unsigned long number, struct ppc64_tlb_batch *batch,
>  		(void)call_block_remove(pix, param, true);
>  }
>  
> +static inline void __init set_hblk_bloc_size(int bpsize, int psize,
> +					     unsigned int block_size)
> +{
> +	struct mmu_psize_def *def = &mmu_psize_defs[bpsize];
> +
> +	if (block_size > def->hblk[psize])
> +		def->hblk[psize] = block_size;
> +}
> +
> +static inline void __init check_lp_set_hblk(unsigned int lp,
> +					    unsigned int block_size)
> +{
> +	unsigned int bpsize, psize;
> +
> +
> +	/* First, check the L bit, if not set, this means 4K */
> +	if ((lp & 0x80) == 0) {
> +		set_hblk_bloc_size(MMU_PAGE_4K, MMU_PAGE_4K, block_size);
> +		return;
> +	}
> +
> +	/* PAPR says to look at bits 2-7 (0 = MSB) */
> +	lp &= 0x3f;
> +	for (bpsize = 0; bpsize < MMU_PAGE_COUNT; bpsize++) {
> +		struct mmu_psize_def *def =  &mmu_psize_defs[bpsize];
> +
> +		for (psize = 0; psize < MMU_PAGE_COUNT; psize++) {
> +			if (def->penc[psize] == lp) {
> +				set_hblk_bloc_size(bpsize, psize, block_size);
> +				return;
> +			}
> +		}
> +	}
> +}
> +
> +#define SPLPAR_TLB_BIC_TOKEN		50
> +#define SPLPAR_TLB_BIC_MAXLENGTH	(MMU_PAGE_COUNT*2 + 10)
> +static int __init read_tlbbi_characteristics(void)
> +{
> +	int call_status;
> +	unsigned char local_buffer[SPLPAR_TLB_BIC_MAXLENGTH];
> +	int len, idx, bpsize;
> +
> +	if (!firmware_has_feature(FW_FEATURE_BLOCK_REMOVE)) {
> +		pr_info("H_BLOCK_REMOVE is not supported");
> +		return 0;
> +	}
> +
> +	memset(local_buffer, 0, SPLPAR_TLB_BIC_MAXLENGTH);
> +
> +	spin_lock(&rtas_data_buf_lock);
> +	memset(rtas_data_buf, 0, RTAS_DATA_BUF_SIZE);
> +	call_status = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
> +				NULL,
> +				SPLPAR_TLB_BIC_TOKEN,
> +				__pa(rtas_data_buf),
> +				RTAS_DATA_BUF_SIZE);
> +	memcpy(local_buffer, rtas_data_buf, SPLPAR_TLB_BIC_MAXLENGTH);
> +	local_buffer[SPLPAR_TLB_BIC_MAXLENGTH - 1] = '\0';
> +	spin_unlock(&rtas_data_buf_lock);
> +
> +	if (call_status != 0) {
> +		pr_warn("%s %s Error calling get-system-parameter (0x%x)\n",
> +			__FILE__, __func__, call_status);
> +		return 0;
> +	}
> +
> +	/*
> +	 * The first two (2) bytes of the data in the buffer are the length of
> +	 * the returned data, not counting these first two (2) bytes.
> +	 */
> +	len = local_buffer[0] * 256 + local_buffer[1] + 2;
> +	if (len >= SPLPAR_TLB_BIC_MAXLENGTH) {
> +		pr_warn("%s too large returned buffer %d", __func__, len);
> +		return 0;
> +	}
> +
> +	idx = 2;
> +	while (idx < len) {
> +		unsigned int block_size = local_buffer[idx++];
> +		unsigned int npsize;
> +
> +		if (!block_size)
> +			break;
> +
> +		block_size = 1 << block_size;
> +		if (block_size != 8)
> +			/* We only support 8 bytes size TLB invalidate buffer */
> +			pr_warn("Unsupported H_BLOCK_REMOVE block size : %d\n",
> +				block_size);

Should we skip setting block size if we find block_size != 8? Also can
we avoid doing that pr_warn in loop and only warn if we don't find
block_size 8 in the invalidate characteristics array? 

> +
> +		for (npsize = local_buffer[idx++];  npsize > 0; npsize--)
> +			check_lp_set_hblk((unsigned int) local_buffer[idx++],
> +					  block_size);
> +	}
> +
> +	for (bpsize = 0; bpsize < MMU_PAGE_COUNT; bpsize++)
> +		for (idx = 0; idx < MMU_PAGE_COUNT; idx++)
> +			if (mmu_psize_defs[bpsize].hblk[idx])
> +				pr_info("H_BLOCK_REMOVE supports base psize:%d psize:%d block size:%d",
> +					bpsize, idx,
> +					mmu_psize_defs[bpsize].hblk[idx]);
> +
> +	return 0;
> +}
> +machine_arch_initcall(pseries, read_tlbbi_characteristics);
> +
>  /*
>   * Take a spinlock around flushes to avoid bouncing the hypervisor tlbie
>   * lock.
> -- 
> 2.23.0