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Subject: Re: [PATCH 3/3] powerpc/mm: call H_BLOCK_REMOVE when supported
To:     Laurent Dufour <ldufour@linux.ibm.com>, mpe@ellerman.id.au,
        benh@kernel.crashing.org, paulus@samba.org, npiggin@gmail.com
Cc:     linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <20190830120712.22971-1-ldufour@linux.ibm.com>
 <20190830120712.22971-4-ldufour@linux.ibm.com>
From:   "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Message-ID: <5bcd3da7-1bc2-f3f9-3ed2-e3aa0bb540bd@linux.ibm.com>
Date:   Thu, 12 Sep 2019 19:50:14 +0530
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On 8/30/19 5:37 PM, Laurent Dufour wrote:
> Instead of calling H_BLOCK_REMOVE all the time when the feature is
> exhibited, call this hcall only when the couple base page size, page size
> is supported as reported by the TLB Invalidate Characteristics.
> 

supported is not actually what we are checking here. We are checking 
whether the base page size actual page size remove can be done in chunks 
of 8 blocks. If we don't support 8 block you fallback to bulk 
invalidate. May be update the commit message accordingly?


> For regular pages and hugetlb, the assumption is made that the page size is
> equal to the base page size. For THP the page size is assumed to be 16M.
> 
> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
> ---
>   arch/powerpc/platforms/pseries/lpar.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
> index 375e19b3cf53..ef3dbf108a65 100644
> --- a/arch/powerpc/platforms/pseries/lpar.c
> +++ b/arch/powerpc/platforms/pseries/lpar.c
> @@ -1143,7 +1143,11 @@ static inline void __pSeries_lpar_hugepage_invalidate(unsigned long *slot,
>   	if (lock_tlbie)
>   		spin_lock_irqsave(&pSeries_lpar_tlbie_lock, flags);
>   
> -	if (firmware_has_feature(FW_FEATURE_BLOCK_REMOVE))
> +	/*
> +	 * Assuming THP size is 16M, and we only support 8 bytes size buffer
> +	 * for the momment.
> +	 */
> +	if (mmu_psize_defs[psize].hblk[MMU_PAGE_16M] == 8)
>   		hugepage_block_invalidate(slot, vpn, count, psize, ssize);
>   	else
>   		hugepage_bulk_invalidate(slot, vpn, count, psize, ssize);


So we don't use block invalidate if blocksize is != 8.


> @@ -1437,7 +1441,10 @@ static void pSeries_lpar_flush_hash_range(unsigned long number, int local)
>   	if (lock_tlbie)
>   		spin_lock_irqsave(&pSeries_lpar_tlbie_lock, flags);
>   
> -	if (firmware_has_feature(FW_FEATURE_BLOCK_REMOVE)) {
> +	/*
> +	 * Currently, we only support 8 bytes size buffer in do_block_remove().
> +	 */
> +	if (mmu_psize_defs[batch->psize].hblk[batch->psize] == 8) {
>   		do_block_remove(number, batch, param);
>   		goto out;
>   	}
> 

-aneesh