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Re: [PATCH v5 8/8] s390: guest support for diagnose 0x318
From: |
Thomas Huth |
Subject: |
Re: [PATCH v5 8/8] s390: guest support for diagnose 0x318 |
Date: |
Fri, 11 Sep 2020 17:14:05 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 |
On 11/09/2020 17.08, Thomas Huth wrote:
> On 10/09/2020 11.36, Collin Walling wrote:
>> DIAGNOSE 0x318 (diag318) is an s390 instruction that allows the storage
>> of diagnostic information that is collected by the firmware in the case
>> of hardware/firmware service events.
>>
>> QEMU handles the instruction by storing the info in the CPU state. A
>> subsequent register sync will communicate the data to the hypervisor.
>>
>> QEMU handles the migration via a VM State Description.
>>
>> This feature depends on the Extended-Length SCCB (els) feature. If
>> els is not present, then a warning will be printed and the SCLP bit
>> that allows the Linux kernel to execute the instruction will not be
>> set.
>>
>> Availability of this instruction is determined by byte 134 (aka fac134)
>> bit 0 of the SCLP Read Info block. This coincidentally expands into the
>> space used for CPU entries, which means VMs running with the diag318
>> capability may not be able to read information regarding all CPUs
>> unless the guest kernel supports an extended-length SCCB.
>>
>> This feature is not supported in protected virtualization mode.
>>
>> Signed-off-by: Collin Walling <walling@linux.ibm.com>
>> Acked-by: Janosch Frank <frankja@linux.ibm.com>
>> ---
>> hw/s390x/sclp.c | 5 +++++
>> include/hw/s390x/sclp.h | 3 +++
>> target/s390x/cpu.h | 2 ++
>> target/s390x/cpu_features.h | 1 +
>> target/s390x/cpu_features_def.h.inc | 3 +++
>> target/s390x/cpu_models.c | 1 +
>> target/s390x/gen-features.c | 1 +
>> target/s390x/kvm.c | 31 +++++++++++++++++++++++++++++
>> target/s390x/machine.c | 17 ++++++++++++++++
>> 9 files changed, 64 insertions(+)
>>
>> diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
>> index 87d468087b..ad5d70e14d 100644
>> --- a/hw/s390x/sclp.c
>> +++ b/hw/s390x/sclp.c
>> @@ -139,6 +139,11 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
>> s390_get_feat_block(S390_FEAT_TYPE_SCLP_CONF_CHAR_EXT,
>> read_info->conf_char_ext);
>>
>> + if (s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB)) {
>> + s390_get_feat_block(S390_FEAT_TYPE_SCLP_FAC134,
>> + &read_info->fac134);
>> + }
>
> Wasn't this feature also possible if there are less than 240 CPUs? Or do
> I mix that up with something else? ... well, maybe it's best anyway if
> we only allow this when ELS is enabled.
Hmmm, looking at the location of fac134 (i.e. offset 134) and the
previous location of the CPU entries (i.e. offset 128), I think I just
mixed this up with something different. So please never mind this question.
Thomas
- Re: [PATCH v5 2/8] s390/sclp: rework sclp boundary checks, (continued)
[PATCH v5 6/8] s390/sclp: add extended-length sccb support for kvm guest, Collin Walling, 2020/09/10
[PATCH v5 8/8] s390: guest support for diagnose 0x318, Collin Walling, 2020/09/10
[PATCH v5 7/8] s390/kvm: header sync for diag318, Collin Walling, 2020/09/10