Re: [PATCH v9 2/2] s390/kvm: diagnose 0x318 sync and reset

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 23.06.20 10:42, Thomas Huth wrote:
> On 22/06/2020 17.46, Collin Walling wrote:
>> DIAGNOSE 0x318 (diag318) sets information regarding the environment
>> the VM is running in (Linux, z/VM, etc) and is observed via
>> firmware/service events.
>>
>> This is a privileged s390x instruction that must be intercepted by
>> SIE. Userspace handles the instruction as well as migration. Data
>> is communicated via VCPU register synchronization.
>>
>> The Control Program Name Code (CPNC) is stored in the SIE block. The
>> CPNC along with the Control Program Version Code (CPVC) are stored
>> in the kvm_vcpu_arch struct.
>>
>> This data is reset on load normal and clear resets.
>>
>> Signed-off-by: Collin Walling <walling@linux.ibm.com>
>> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
>> ---
>>  arch/s390/include/asm/kvm_host.h |  4 +++-
>>  arch/s390/include/uapi/asm/kvm.h |  5 ++++-
>>  arch/s390/kvm/kvm-s390.c         | 11 ++++++++++-
>>  arch/s390/kvm/vsie.c             |  1 +
>>  include/uapi/linux/kvm.h         |  1 +
>>  5 files changed, 19 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
>> index 3d554887794e..8bdf6f1607ca 100644
>> --- a/arch/s390/include/asm/kvm_host.h
>> +++ b/arch/s390/include/asm/kvm_host.h
>> @@ -260,7 +260,8 @@ struct kvm_s390_sie_block {
>>  	__u32	scaol;			/* 0x0064 */
>>  	__u8	sdf;			/* 0x0068 */
>>  	__u8    epdx;			/* 0x0069 */
>> -	__u8    reserved6a[2];		/* 0x006a */
>> +	__u8	cpnc;			/* 0x006a */
>> +	__u8	reserved6b;		/* 0x006b */
>>  	__u32	todpr;			/* 0x006c */
>>  #define GISA_FORMAT1 0x00000001
>>  	__u32	gd;			/* 0x0070 */
>> @@ -745,6 +746,7 @@ struct kvm_vcpu_arch {
>>  	bool gs_enabled;
>>  	bool skey_enabled;
>>  	struct kvm_s390_pv_vcpu pv;
>> +	union diag318_info diag318_info;
>>  };
>>  
>>  struct kvm_vm_stat {
>> diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
>> index 436ec7636927..2ae1b660086c 100644
>> --- a/arch/s390/include/uapi/asm/kvm.h
>> +++ b/arch/s390/include/uapi/asm/kvm.h
>> @@ -231,11 +231,13 @@ struct kvm_guest_debug_arch {
>>  #define KVM_SYNC_GSCB   (1UL << 9)
>>  #define KVM_SYNC_BPBC   (1UL << 10)
>>  #define KVM_SYNC_ETOKEN (1UL << 11)
>> +#define KVM_SYNC_DIAG318 (1UL << 12)
>>  
>>  #define KVM_SYNC_S390_VALID_FIELDS \
>>  	(KVM_SYNC_PREFIX | KVM_SYNC_GPRS | KVM_SYNC_ACRS | KVM_SYNC_CRS | \
>>  	 KVM_SYNC_ARCH0 | KVM_SYNC_PFAULT | KVM_SYNC_VRS | KVM_SYNC_RICCB | \
>> -	 KVM_SYNC_FPRS | KVM_SYNC_GSCB | KVM_SYNC_BPBC | KVM_SYNC_ETOKEN)
>> +	 KVM_SYNC_FPRS | KVM_SYNC_GSCB | KVM_SYNC_BPBC | KVM_SYNC_ETOKEN | \
>> +	 KVM_SYNC_DIAG318)
>>  
>>  /* length and alignment of the sdnx as a power of two */
>>  #define SDNXC 8
>> @@ -254,6 +256,7 @@ struct kvm_sync_regs {
>>  	__u64 pft;	/* pfault token [PFAULT] */
>>  	__u64 pfs;	/* pfault select [PFAULT] */
>>  	__u64 pfc;	/* pfault compare [PFAULT] */
>> +	__u64 diag318;	/* diagnose 0x318 info */
>>  	union {
>>  		__u64 vrs[32][2];	/* vector registers (KVM_SYNC_VRS) */
>>  		__u64 fprs[16];		/* fp registers (KVM_SYNC_FPRS) */
> 
> It's been a while since I touched kvm_sync_regs the last time ... but
> can your really extend this structure right in the middle without
> breaking older user spaces (ie. QEMUs) ? This is a uapi header ... so I
> think you rather have to add this add the end or e.g. put it into the
> padding2 region or something like that...? Or do I miss something?

Argh. You are right. It should go to the end and not in the middle. Will fixup.