| Message ID | 20190916095543.17496-1-ldufour@linux.ibm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | powerpc/mm: Conditionally call H_BLOCK_REMOVE | expand |
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@linux.ibm.com> for the series. -aneesh
Hi Laurent, Thanks for fixing this, just a few comments. Laurent Dufour <ldufour@linux.ibm.com> writes: > 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: Missing panic :) Also can you put that detail in the 2nd commit, so that it's obvious that it is a fix for an oops. > The PAPR document specifies the TLB Block Invalidate Characteristics which Can you give a section/page number for the PAPR reference. > tells for each couple segment base page size, actual page size, the size of ^ "pair of" is better than "couple" I think > 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. But the hardware that is exhibiting it, by crashing and not booting, is mostly (all?) older hardware. So I think we probably should send it back to stable, otherwise those machines may never get an updated kernel. Can you add Fixes: tags to the commits, they should point at the commit that added H_BLOCK_REMOVE support. cheers > 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 > > Laurent Dufour (2): > powperc/mm: read TLB Block Invalidate Characteristics > powerpc/mm: call H_BLOCK_REMOVE when supported > > .../include/asm/book3s/64/tlbflush-hash.h | 1 + > arch/powerpc/platforms/pseries/lpar.c | 173 +++++++++++++++++- > arch/powerpc/platforms/pseries/setup.c | 1 + > 3 files changed, 173 insertions(+), 2 deletions(-) > > -- > 2.23.0
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 Laurent Dufour (2): powperc/mm: read TLB Block Invalidate Characteristics powerpc/mm: call H_BLOCK_REMOVE when supported .../include/asm/book3s/64/tlbflush-hash.h | 1 + arch/powerpc/platforms/pseries/lpar.c | 173 +++++++++++++++++- arch/powerpc/platforms/pseries/setup.c | 1 + 3 files changed, 173 insertions(+), 2 deletions(-)