Re: [Qemu-devel] [PATCH v1 RFC 3/6] KVM: s390: use facilities and cpu_id per KVM

[Alexander Graf <agraf@suse.de>]

On 16.05.14 16:46, Michael Mueller wrote:
> On Fri, 16 May 2014 13:55:41 +0200
> Alexander Graf <agraf@suse.de> wrote:
>
>> On 13.05.14 16:58, Michael Mueller wrote:
>>> The patch introduces facilities and cpu_ids per virtual machine.
>>> Different virtual machines may want to expose different facilities and
>>> cpu ids to the guest, so let's make them per-vm instead of global.
>>>
>>> In addition this patch renames all ocurrences of *facilities to *fac_list
>>> smilar to the already exiting symbol stfl_fac_list in lowcore.
>>>
>>> Signed-off-by: Michael Mueller <mimu@linux.vnet.ibm.com>
>>> Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
>>> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
>>> ---
>>>    arch/s390/include/asm/kvm_host.h |   7 +++
>>>    arch/s390/kvm/gaccess.c          |   4 +-
>>>    arch/s390/kvm/kvm-s390.c         | 107 +++++++++++++++++++++++++++------------
>>>    arch/s390/kvm/kvm-s390.h         |  23 +++++++--
>>>    arch/s390/kvm/priv.c             |  13 +++--
>>>    5 files changed, 113 insertions(+), 41 deletions(-)
>>>
>>> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
>>> index 38d487a..b4751ba 100644
>>> --- a/arch/s390/include/asm/kvm_host.h
>>> +++ b/arch/s390/include/asm/kvm_host.h
>>> @@ -414,6 +414,12 @@ struct kvm_s390_config {
>>>    	struct kvm_s390_attr_name name;
>>>    };
>>>    
>>> +struct kvm_s390_cpu_model {
>>> +	unsigned long *sie_fac;
>>> +	struct cpuid cpu_id;
>>> +	unsigned long *fac_list;
>>> +};
>>> +
>>>    struct kvm_arch{
>>>    	struct sca_block *sca;
>>>    	debug_info_t *dbf;
>>> @@ -427,6 +433,7 @@ struct kvm_arch{
>>>    	wait_queue_head_t ipte_wq;
>>>    	struct kvm_s390_config *cfg;
>>>    	spinlock_t start_stop_lock;
>>> +	struct kvm_s390_cpu_model model;
>>>    };
>>>    
>>>    #define KVM_HVA_ERR_BAD		(-1UL)
>>> diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
>>> index db608c3..4c7ca40 100644
>>> --- a/arch/s390/kvm/gaccess.c
>>> +++ b/arch/s390/kvm/gaccess.c
>>> @@ -358,8 +358,8 @@ static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long
>>> gva, union asce asce;
>>>    
>>>    	ctlreg0.val = vcpu->arch.sie_block->gcr[0];
>>> -	edat1 = ctlreg0.edat && test_vfacility(8);
>>> -	edat2 = edat1 && test_vfacility(78);
>>> +	edat1 = ctlreg0.edat && test_kvm_facility(vcpu->kvm, 8);
>>> +	edat2 = edat1 && test_kvm_facility(vcpu->kvm, 78);
>>>    	asce.val = get_vcpu_asce(vcpu);
>>>    	if (asce.r)
>>>    		goto real_address;
>>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>>> index 01a5212..a53652f 100644
>>> --- a/arch/s390/kvm/kvm-s390.c
>>> +++ b/arch/s390/kvm/kvm-s390.c
>>> @@ -1,5 +1,5 @@
>>>    /*
>>> - * hosting zSeries kernel virtual machines
>>> + * Hosting zSeries kernel virtual machines
>>>     *
>>>     * Copyright IBM Corp. 2008, 2009
>>>     *
>>> @@ -30,7 +30,6 @@
>>>    #include <asm/pgtable.h>
>>>    #include <asm/nmi.h>
>>>    #include <asm/switch_to.h>
>>> -#include <asm/facility.h>
>>>    #include <asm/sclp.h>
>>>    #include<asm/timex.h>
>>>    #include "kvm-s390.h"
>>> @@ -92,15 +91,33 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
>>>    	{ NULL }
>>>    };
>>>    
>>> -unsigned long *vfacilities;
>>> -static struct gmap_notifier gmap_notifier;
>>> +/* upper facilities limit for kvm */
>>> +unsigned long kvm_s390_fac_list_mask[] = {
>>> +	0xff82fff3f47c2000UL,
>>> +	0x005c000000000000UL,
>>> +};
>>> +
>>> +unsigned long kvm_s390_fac_list_mask_size(void)
>>> +{
>>> +	BUILD_BUG_ON(ARRAY_SIZE(kvm_s390_fac_list_mask) >
>>> +		     S390_ARCH_FAC_MASK_SIZE_U64);
>>> +	return ARRAY_SIZE(kvm_s390_fac_list_mask);
>>> +}
>>>    
>>> -/* test availability of vfacility */
>>> -int test_vfacility(unsigned long nr)
>>> +void kvm_s390_apply_fac_list_mask(unsigned long fac_list[])
>>>    {
>>> -	return __test_facility(nr, (void *) vfacilities);
>>> +	unsigned int i;
>>> +
>>> +	for (i = 0; i < S390_ARCH_FAC_LIST_SIZE_U64; i++) {
>>> +		if (i < kvm_s390_fac_list_mask_size())
>>> +			fac_list[i] &= kvm_s390_fac_list_mask[i];
>>> +		else
>>> +			fac_list[i] &= 0UL;
>>> +	}
>>>    }
>>>    
>>> +static struct gmap_notifier gmap_notifier;
>>> +
>>>    /* Section: not file related */
>>>    int kvm_arch_hardware_enable(void *garbage)
>>>    {
>>> @@ -485,6 +502,30 @@ long kvm_arch_vm_ioctl(struct file *filp,
>>>    	return r;
>>>    }
>>>    
>>> +/* make sure the memory used for fac_list is zeroed */
>>> +void kvm_s390_get_hard_fac_list(unsigned long *fac_list, int size)
>> Hard? Wouldn't "host" make more sense here?
> Renaming "*hard_fac_list" with "*host_fac_list" here and wherever it appears is ok with me.
>
>> I also think it makes sense to expose the native host facility list to
>> user space via an ioctl somehow.
>>
> In which situation do you need the full facility list. Do you have an example?

If you want to just implement -cpu host to get the exact feature set 
that the host gives you, how do you know which set that is?


Alex