[PATCH v2 1/2] powperc/mm: read TLB Block Invalidate Characteristics
Laurent Dufour
ldufour at linux.ibm.com
Fri Sep 20 01:59:16 AEST 2019
Le 18/09/2019 à 15:42, Michael Ellerman a écrit :
> Hi Laurent,
>
> Comments below ...
Hi Michael,
Thanks for your review.
One comment below (at the end).
>
> Laurent Dufour <ldufour at linux.ibm.com> writes:
>> The PAPR document specifies the TLB Block Invalidate Characteristics which
>> tells for each couple segment base page size, actual page size, the size of
> ^
> "pair of" again
>
>> the block the hcall H_BLOCK_REMOVE is supporting.
> ^
> "supports" is fine.
>
>> These characteristics are loaded at boot time in a new table hblkr_size.
>> The table is appart the mmu_psize_def because this is specific to the
> ^
> "separate from"
>
>> pseries architecture.
> ^
> platform
>>
>> A new init service, pseries_lpar_read_hblkr_characteristics() is added to
> ^
> function
>
>> read the characteristics. In that function, the size of the buffer is set
>> to twice the number of known page size, plus 10 bytes to ensure we have
>> enough place. This new init function is called from pSeries_setup_arch().
> ^
> space
>>
>> Signed-off-by: Laurent Dufour <ldufour at linux.ibm.com>
>> ---
>> .../include/asm/book3s/64/tlbflush-hash.h | 1 +
>> arch/powerpc/platforms/pseries/lpar.c | 138 ++++++++++++++++++
>> arch/powerpc/platforms/pseries/setup.c | 1 +
>> 3 files changed, 140 insertions(+)
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
>> index 64d02a704bcb..74155cc8cf89 100644
>> --- a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
>> +++ b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
>> @@ -117,4 +117,5 @@ extern void __flush_hash_table_range(struct mm_struct *mm, unsigned long start,
>> unsigned long end);
>> extern void flush_tlb_pmd_range(struct mm_struct *mm, pmd_t *pmd,
>> unsigned long addr);
>> +extern void pseries_lpar_read_hblkr_characteristics(void);
>
> This doesn't need "extern", and also should go in
> arch/powerpc/platforms/pseries/pseries.h as it's local to that directory.
>
> You're using "hblkr" in a few places, can we instead make it "hblkrm" -
> "rm" is a well known abbreviation for "remove".
>
>
>> diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
>> index 36b846f6e74e..98a5c2ff9a0b 100644
>> --- a/arch/powerpc/platforms/pseries/lpar.c
>> +++ b/arch/powerpc/platforms/pseries/lpar.c
>> @@ -56,6 +56,15 @@ EXPORT_SYMBOL(plpar_hcall);
>> EXPORT_SYMBOL(plpar_hcall9);
>> EXPORT_SYMBOL(plpar_hcall_norets);
>>
>> +/*
>> + * H_BLOCK_REMOVE supported block size for this page size in segment who's base
>> + * page size is that page size.
>> + *
>> + * The first index is the segment base page size, the second one is the actual
>> + * page size.
>> + */
>> +static int hblkr_size[MMU_PAGE_COUNT][MMU_PAGE_COUNT];
>
> Can you make that __ro_after_init, it goes at the end, eg:
>
> static int hblkr_size[MMU_PAGE_COUNT][MMU_PAGE_COUNT] __ro_after_init;
>
>> @@ -1311,6 +1320,135 @@ static void do_block_remove(unsigned long number, struct ppc64_tlb_batch *batch,
>> (void)call_block_remove(pix, param, true);
>> }
>>
>> +/*
>> + * TLB Block Invalidate Characteristics These characteristics define the size of
> ^
> newline before here?
>
>> + * the block the hcall H_BLOCK_REMOVE is able to process for each couple segment
>> + * base page size, actual page size.
>> + *
>> + * The ibm,get-system-parameter properties is returning a buffer with the
>> + * following layout:
>> + *
>> + * [ 2 bytes size of the RTAS buffer (without these 2 bytes) ]
> ^
> "excluding"
>
>> + * -----------------
>> + * TLB Block Invalidate Specifiers:
>> + * [ 1 byte LOG base 2 of the TLB invalidate block size being specified ]
>> + * [ 1 byte Number of page sizes (N) that are supported for the specified
>> + * TLB invalidate block size ]
>> + * [ 1 byte Encoded segment base page size and actual page size
>> + * MSB=0 means 4k segment base page size and actual page size
>> + * MSB=1 the penc value in mmu_psize_def ]
>> + * ...
>> + * -----------------
>> + * Next TLB Block Invalidate Specifiers...
>> + * -----------------
>> + * [ 0 ]
>> + */
>> +static inline void __init set_hblk_bloc_size(int bpsize, int psize,
>> + unsigned int block_size)
>
> "static inline" and __init are sort of contradictory.
>
> Just make it "static void __init" and the compiler will inline it
> anyway, but if it decides not to the section will be correct.
>
> This one uses "hblk"? Should it be set_hblkrm_block_size() ?
>
>> +{
>> + if (block_size > hblkr_size[bpsize][psize])
>> + hblkr_size[bpsize][psize] = block_size;
>> +}
>> +
>> +/*
>> + * Decode the Encoded segment base page size and actual page size.
>> + * PAPR specifies with bit 0 as MSB:
>> + * - bit 0 is the L bit
>> + * - bits 2-7 are the penc value
>
> Can we just convert those to normal bit ordering for the comment, eg:
>
> PAPR specifies:
> - bit 7 is the L bit
> - bits 0-5 are the penc value
>
>> + * If the L bit is 0, this means 4K segment base page size and actual page size
>> + * otherwise the penc value should be readed.
> ^
> "read" ?
>> + */
>> +#define HBLKR_L_BIT_MASK 0x80
>
> "HBLKRM_L_MASK" would do I think?
>
>> +#define HBLKR_PENC_MASK 0x3f
>> +static inline void __init check_lp_set_hblk(unsigned int lp,
>> + unsigned int block_size)
>> +{
>> + unsigned int bpsize, psize;
>> +
>
> One blank line is sufficient :)
>
>> +
>> + /* First, check the L bit, if not set, this means 4K */
>> + if ((lp & HBLKR_L_BIT_MASK) == 0) {
>> + set_hblk_bloc_size(MMU_PAGE_4K, MMU_PAGE_4K, block_size);
>> + return;
>> + }
>> +
>> + lp &= HBLKR_PENC_MASK;
>> + for (bpsize = 0; bpsize < MMU_PAGE_COUNT; bpsize++) {
>> + struct mmu_psize_def *def = &mmu_psize_defs[bpsize];
> ^
> stray space there
>> +
>> + 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)
>
> The +10 is just a guess I think?
>
> If I'm counting right that ends up as 42 bytes, which is not much at
> all. You could probably just make it a cache line, 128 bytes, which
> should be plenty of space?
>
>> +void __init pseries_lpar_read_hblkr_characteristics(void)
>> +{
>> + int call_status;
>
> This should be grouped with the other ints below on one line.
>
>> + 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");
>
> That's going to trigger on a lot of older machines, and all KVM VMs, so
> just return silently.
>
>> + return;
>> + }
>> +
>> + memset(local_buffer, 0, SPLPAR_TLB_BIC_MAXLENGTH);
>
> Here you memset the whole buffer ...
>
>> + 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);
>
> But then here you memcpy over the entire buffer, making the memset above
> unnecessary.
>
>> + 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);
>
> __FILE__ and __func__ is pretty verbose for what should be a rare case
> (I realise you copied that from existing code).
>
> pr_warn("Error calling get-system-parameter(%d, ...) (0x%x)\n",
> SPLPAR_TLB_BIC_TOKEN, call_status);
>
> Should do I think?
>
>> + return;
>> + }
>> +
>> + /*
>> + * 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;
>
> This took me a minute to parse. I guess I was expecting something more
> like:
> len = be16_to_cpu(local_buffer) + 2;
>
> ??
>
>> + if (len >= SPLPAR_TLB_BIC_MAXLENGTH) {
>
> I think it's allowed for len to be == SPLPAR_TLB_BIC_MAXLENGTH isn't it?
>
>> + pr_warn("%s too large returned buffer %d", __func__, len);
>> + return;
>> + }
>> +
>> + idx = 2;
>> + while (idx < len) {
>> + unsigned int block_size = local_buffer[idx++];
>
> This is a little subtle, local_buffer is char, so no endian issue, but
> you're loading that into an unsigned int which makes it look like there
> should be an endian swap.
>
> Maybe instead do:
> u8 block_shift = local_buffer[idx++];
> u32 block_size;
>
> if (!block_shift)
> break;
>
> block_size = 1 << block_shift;
>
> ??
>
>> + unsigned int npsize;
>> +
>> + if (!block_size)
>> + break;
>> +
>> + block_size = 1 << block_size;
>> +
>> + for (npsize = local_buffer[idx++]; npsize > 0; npsize--)
>> + check_lp_set_hblk((unsigned int) local_buffer[idx++],
>> + block_size);
>
> This could overflow if npsize is too big. I think you can just ad
> "&& idx < len" to the for condition to make it safe?
>
>> + }
>> +
>> + for (bpsize = 0; bpsize < MMU_PAGE_COUNT; bpsize++)
>> + for (idx = 0; idx < MMU_PAGE_COUNT; idx++)
>> + if (hblkr_size[bpsize][idx])
>> + pr_info("H_BLOCK_REMOVE supports base psize:%d psize:%d block size:%d",
>> + bpsize, idx, hblkr_size[bpsize][idx]);
>
> I think this is probably too verbose, except for debugging. Probably
> just remove it?
I'd like to keep that displayed because this is the only way to get these
values.
I tried to use pr_debug() and rely on a dyndbg kernel command line option,
but the dynamic debug system is not yet initialised at this time of boot.
When a system is booting, those messages are interleaved with other user
cryptic messages ;):
[ 0.000000] numa: NODE_DATA [mem 0x7ffdd7000-0x7ffddbfff]
[ 0.000000] numa: NODE_DATA(0) on node 2
[ 0.000000] numa: NODE_DATA [mem 0x7ffdd2000-0x7ffdd6fff]
[ 0.000000] rfi-flush: fallback displacement flush available
[ 0.000000] rfi-flush: mttrig type flush available
[ 0.000000] count-cache-flush: full software flush sequence enabled.
[ 0.000000] stf-barrier: eieio barrier available
[ 0.000000] lpar: H_BLOCK_REMOVE supports base psize:0 psize:0 block size:8
[ 0.000000] lpar: H_BLOCK_REMOVE supports base psize:0 psize:2 block size:8
[ 0.000000] lpar: H_BLOCK_REMOVE supports base psize:0 psize:10 block size:8
[ 0.000000] lpar: H_BLOCK_REMOVE supports base psize:2 psize:2 block size:8
[ 0.000000] lpar: H_BLOCK_REMOVE supports base psize:2 psize:10 block size:8
[ 0.000000] PPC64 nvram contains 15360 bytes
[ 0.000000] barrier-nospec: using ORI speculation barrier
[ 0.000000] Zone ranges:
[ 0.000000] Normal [mem 0x0000000000000000-0x00000007ffffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 2: [mem 0x0000000000000000-0x00000007ffffffff]
[ 0.000000] Could not find start_pfn for node 0
Is this an issue to keep those lines ?
Cheers
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