From: Laurent Dufour <ldufour@linux.ibm.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org,
npiggin@gmail.com
Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/3] powerpc/mm: Conditionally call H_BLOCK_REMOVE
Date: Fri, 13 Sep 2019 13:09:42 +0200 [thread overview]
Message-ID: <6d9ca38f-2b80-a2a5-491e-d818a3ebcd32@linux.ibm.com> (raw)
In-Reply-To: <1c499131-36f2-9d89-ed4c-5cb59a08398d@linux.ibm.com>
Le 12/09/2019 à 15:44, Aneesh Kumar K.V a écrit :
> On 8/30/19 5:37 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.
>>
>> On some system, the hypervisor may not support all the combination of
>> segment base page size and page size. When this happens the hcall is
>> returning H_PARAM, which is triggering a BUG_ON check leading to a panic.
>>
>> The PAPR document is specifying a TLB Block Invalidate Characteristics item
>> detailing which couple base page size, page size the hypervisor is
>> supporting through H_BLOCK_REMOVE. Furthermore, the characteristics are
>> also providing the size of the block the hcall could process.
>>
>> Supporting various block size seems not needed as all systems I was able to
>> play with was support an 8 addresses block size, which is the maximum
>> through the hcall. Supporting various size may 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 initializing the penc values for each page size to an
>> invalid value to be able to detect those which have been initialized as 0
>> is a valid value.
>>
>> The second patch is reading the characteristic through the hcall
>> ibm,get-system-parameter and record the supported block size for each page
>> size.
>>
>> The third 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.
>>
>
> So ibm,segment-page-sizes indicates wether we support a combination of base
> page size and actual page size. You are suggesting that the value reported
> by that is not correct? Can you also share the early part of dmesg as below.
I'm not saying that the value reported by ibm,segment-page-sizes are
incorrect, I'm saying that some couple are not supported by the hcall
H_BLOCK_REMOVE.
May be should I change the second sentence by
On some system, the hypervisor may not support all the combination of
segment base page size and page size for the hcall H_BLOCK_REMOVE. When
this happens the hcall is returning H_PARAM, which is triggering a BUG_ON
check leading to a panic.
Is that clear enough now ?
>
> [ 0.000000] hash-mmu: Page sizes from device-tree:
> [ 0.000000] hash-mmu: base_shift=12: shift=12, sllp=0x0000,
> avpnm=0x00000000, tlbiel=1, penc=0
> [ 0.000000] hash-mmu: base_shift=12: shift=16, sllp=0x0000,
> avpnm=0x00000000, tlbiel=1, penc=7
> [ 0.000000] hash-mmu: base_shift=12: shift=24, sllp=0x0000,
> avpnm=0x00000000, tlbiel=1, penc=56
> [ 0.000000] hash-mmu: base_shift=16: shift=16, sllp=0x0110,
> avpnm=0x00000000, tlbiel=1, penc=1
> [ 0.000000] hash-mmu: base_shift=16: shift=24, sllp=0x0110,
> avpnm=0x00000000, tlbiel=1, penc=8
> [ 0.000000] hash-mmu: base_shift=24: shift=24, sllp=0x0100,
> avpnm=0x00000001, tlbiel=0, penc=0
> [ 0.000000] hash-mmu: base_shift=34: shift=34, sllp=0x0120,
> avpnm=0x000007ff, tlbiel=0, penc=3
>
> That shows different base page size and actual page size combination.
>
>
>> Laurent Dufour (3):
>> powerpc/mm: Initialize the HPTE encoding values
>> powperc/mm: read TLB Block Invalidate Characteristics
>> powerpc/mm: call H_BLOCK_REMOVE when supported
>>
>> arch/powerpc/include/asm/book3s/64/mmu.h | 3 +
>> arch/powerpc/mm/book3s64/hash_utils.c | 8 +-
>> arch/powerpc/platforms/pseries/lpar.c | 118 ++++++++++++++++++++++-
>> 3 files changed, 125 insertions(+), 4 deletions(-)
>>
>
>
> -aneesh
prev parent reply other threads:[~2019-09-13 11:12 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-30 12:07 [PATCH 0/3] powerpc/mm: Conditionally call H_BLOCK_REMOVE Laurent Dufour
2019-08-30 12:07 ` [PATCH 1/3] powerpc/mm: Initialize the HPTE encoding values Laurent Dufour
2019-09-12 13:32 ` Aneesh Kumar K.V
2019-09-12 13:37 ` Aneesh Kumar K.V
2019-09-13 10:56 ` Laurent Dufour
2019-08-30 12:07 ` [PATCH 2/3] powperc/mm: read TLB Block Invalidate Characteristics Laurent Dufour
2019-09-12 14:16 ` Aneesh Kumar K.V
2019-09-13 13:55 ` Laurent Dufour
2019-09-12 14:44 ` Aneesh Kumar K.V
2019-09-12 19:26 ` Laurent Dufour
2019-09-13 2:00 ` Aneesh Kumar K.V
2019-09-13 9:10 ` Laurent Dufour
2019-08-30 12:07 ` [PATCH 3/3] powerpc/mm: call H_BLOCK_REMOVE when supported Laurent Dufour
2019-09-12 14:20 ` Aneesh Kumar K.V
2019-09-13 13:16 ` Laurent Dufour
2019-09-12 13:44 ` [PATCH 0/3] powerpc/mm: Conditionally call H_BLOCK_REMOVE Aneesh Kumar K.V
2019-09-13 11:09 ` Laurent Dufour [this message]
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