Re: [PATCH v2 0/2] powerpc/mm: Conditionally call H_BLOCK_REMOVE

[Aneesh Kumar K.V]

On 9/16/19 3:25 PM, Laurent Dufour wrote:
> Since the commit ba2dd8a26baa ("powerpc/pseries/mm: call H_BLOCK_REMOVE"),
> the call to H_BLOCK_REMOVE is always done if the feature is exhibited.
>
> However, the hypervisor may not support all the block size for the hcall
> H_BLOCK_REMOVE depending on the segment base page size and actual page
> size.
>
> When unsupported block size is used, the hcall H_BLOCK_REMOVE is returning
> H_PARAM, which is triggering a BUG_ON check leading to a panic like this:
>
> The PAPR document specifies the TLB Block Invalidate Characteristics which
> tells for each couple segment base page size, actual page size, the size of
> the block the hcall H_BLOCK_REMOVE is supporting.
>
> Supporting various block sizes doesn't seem needed at that time since all
> systems I was able to play with was supporting an 8 addresses block size,
> which is the maximum through the hcall, or none at all. Supporting various
> size would complexify the algorithm in call_block_remove() so unless this
> is required, this is not done.
>
> In the case of block size different from 8, a warning message is displayed
> at boot time and that block size will be ignored checking for the
> H_BLOCK_REMOVE support.
>
> Due to the minimal amount of hardware showing a limited set of
> H_BLOCK_REMOVE supported page size, I don't think there is a need to push
> this series to the stable mailing list.
>
> The first patch is reading the characteristic through the hcall
> ibm,get-system-parameter and record the supported block size for each page
> size.  The second patch is changing the check used to detect the
> H_BLOCK_REMOVE availability to take care of the base page size and page
> size couple.
>
> Changes since V1:
>
>   - Remove penc initialisation, this is already done in
>     mmu_psize_set_default_penc()
>   - Add details on the TLB Block Invalidate Characteristics's buffer format
>   - Introduce #define instead of using direct numerical values
>   - Function reading the characteristics is now directly called from
>     pSeries_setup_arch()
>   - The characteristics are now stored in a dedciated table static to lpar.c

you can use

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>

for the series.

-aneesh