Re: [PATCH v9 07/22] KVM: s390: refactor crypto initialization

[Tony Krowiak <akrowiak@linux.ibm.com>]

On 08/20/2018 12:41 PM, David Hildenbrand wrote:
> On 13.08.2018 23:48, Tony Krowiak wrote:
>> From: Tony Krowiak <akrowiak@linux.ibm.com>
>>
>> This patch refactors the code that initializes and sets up the
>> crypto configuration for a guest. The following changes are
>> implemented via this patch:
>>
>> 1. Prior to the introduction of AP device virtualization, it
>>     was not necessary to provide guest access to the CRYCB
>>     unless the MSA extension 3 (MSAX3) facility was installed
>>     on the host system. With the introduction of AP device
>>     virtualization, the CRYCB must be made accessible to the
>>     guest if the AP instructions are installed on the host
>>     and are to be provided to the guest.
>>
>> 2. Introduces a flag indicating AP instructions executed on
>>     the guest shall be interpreted by the firmware. It is
>>     initialized to indicate AP instructions are to be
>>     to be interpreted and is used to set the SIE bit for
>>     each vcpu during vcpu setup.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
>> Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
>> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> Acked-by: Janosch Frank <frankja@linux.ibm.com>
>> Tested-by: Michael Mueller <mimu@linux.ibm.com>
>> Tested-by: Farhan Ali <alifm@linux.ibm.com>
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> ---
>>   arch/s390/include/asm/kvm_host.h |    2 +
>>   arch/s390/include/uapi/asm/kvm.h |    1 +
>>   arch/s390/kvm/kvm-s390.c         |   81 +++++++++++++++++++-------------------
>>   3 files changed, 44 insertions(+), 40 deletions(-)
>>
>> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
>> index af39561..4a739d4 100644
>> --- a/arch/s390/include/asm/kvm_host.h
>> +++ b/arch/s390/include/asm/kvm_host.h
>> @@ -187,6 +187,7 @@ struct kvm_s390_sie_block {
>>   #define ECA_AIV		0x00200000
>>   #define ECA_VX		0x00020000
>>   #define ECA_PROTEXCI	0x00002000
>> +#define ECA_APIE	0x00000008
>>   #define ECA_SII		0x00000001
>>   	__u32	eca;			/* 0x004c */
>>   #define ICPT_INST	0x04
>> @@ -256,6 +257,7 @@ struct kvm_s390_sie_block {
>>   	__u8	reservede4[4];		/* 0x00e4 */
>>   	__u64	tecmc;			/* 0x00e8 */
>>   	__u8	reservedf0[12];		/* 0x00f0 */
>> +#define CRYCB_FORMAT_MASK 0x00000003
>>   #define CRYCB_FORMAT1 0x00000001
>>   #define CRYCB_FORMAT2 0x00000003
>>   	__u32	crycbd;			/* 0x00fc */
>> diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
>> index 4cdaa55..a580dec 100644
>> --- a/arch/s390/include/uapi/asm/kvm.h
>> +++ b/arch/s390/include/uapi/asm/kvm.h
>> @@ -130,6 +130,7 @@ struct kvm_s390_vm_cpu_machine {
>>   #define KVM_S390_VM_CPU_FEAT_PFMFI	11
>>   #define KVM_S390_VM_CPU_FEAT_SIGPIF	12
>>   #define KVM_S390_VM_CPU_FEAT_KSS	13
>> +#define KVM_S390_VM_CPU_FEAT_AP		14
>>   struct kvm_s390_vm_cpu_feat {
>>   	__u64 feat[16];
>>   };
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index 19f4f44..f7de123 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -40,6 +40,7 @@
>>   #include <asm/sclp.h>
>>   #include <asm/cpacf.h>
>>   #include <asm/timex.h>
>> +#include <asm/ap.h>
>>   #include "kvm-s390.h"
>>   #include "gaccess.h"
>>   
>> @@ -1881,49 +1882,37 @@ long kvm_arch_vm_ioctl(struct file *filp,
>>   	return r;
>>   }
>>   
>> -static int kvm_s390_query_ap_config(u8 *config)
>> -{
>> -	u32 fcn_code = 0x04000000UL;
>> -	u32 cc = 0;
>> -
>> -	memset(config, 0, 128);
>> -	asm volatile(
>> -		"lgr 0,%1\n"
>> -		"lgr 2,%2\n"
>> -		".long 0xb2af0000\n"		/* PQAP(QCI) */
>> -		"0: ipm %0\n"
>> -		"srl %0,28\n"
>> -		"1:\n"
>> -		EX_TABLE(0b, 1b)
>> -		: "+r" (cc)
>> -		: "r" (fcn_code), "r" (config)
>> -		: "cc", "0", "2", "memory"
>> -	);
>> -
>> -	return cc;
>> -}
>> -
>>   static int kvm_s390_apxa_installed(void)
>>   {
>> -	u8 config[128];
>> -	int cc;
>> +	struct ap_config_info info;
>>   
>> -	if (test_facility(12)) {
>> -		cc = kvm_s390_query_ap_config(config);
>> -
>> -		if (cc)
>> -			pr_err("PQAP(QCI) failed with cc=%d", cc);
>> -		else
>> -			return config[0] & 0x40;
>> +	if (ap_instructions_available()) {
>> +		if (ap_qci(&info) == 0)
>> +			return info.apxa;
>>   	}
>>   
>>   	return 0;
>>   }
>>   
>> +/*
>> + * The format of the crypto control block (CRYCB) is specified in the 3 low
>> + * order bits of the CRYCB designation (CRYCBD) field as follows:
>> + * Format 0: Neither the message security assist extension 3 (MSAX3) nor the
>> + *	     AP extended addressing (APXA) facility are installed.
>> + * Format 1: The APXA facility is not installed but the MSAX3 facility is.
>> + * Format 2: Both the APXA and MSAX3 facilities are installed
>> + */
>>   static void kvm_s390_set_crycb_format(struct kvm *kvm)
>>   {
>>   	kvm->arch.crypto.crycbd = (__u32)(unsigned long) kvm->arch.crypto.crycb;
>>   
>> +	/* Clear the CRYCB format bits - i.e., set format 0 by default */
>> +	kvm->arch.crypto.crycbd &= ~(CRYCB_FORMAT_MASK);
>> +
>> +	/* Check whether MSAX3 is installed */
>> +	if (!test_kvm_facility(kvm, 76))
>> +		return;
>> +
>>   	if (kvm_s390_apxa_installed())
>>   		kvm->arch.crypto.crycbd |= CRYCB_FORMAT2;
>>   	else
>> @@ -1941,12 +1930,12 @@ static u64 kvm_s390_get_initial_cpuid(void)
>>   
>>   static void kvm_s390_crypto_init(struct kvm *kvm)
>>   {
>> -	if (!test_kvm_facility(kvm, 76))
>> -		return;
>> -
>>   	kvm->arch.crypto.crycb = &kvm->arch.sie_page2->crycb;
>>   	kvm_s390_set_crycb_format(kvm);
>>   
>> +	if (!test_kvm_facility(kvm, 76))
>> +		return;
>> +
>>   	/* Enable AES/DEA protected key functions by default */
>>   	kvm->arch.crypto.aes_kw = 1;
>>   	kvm->arch.crypto.dea_kw = 1;
>> @@ -2474,17 +2463,29 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
>>   
>>   static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu)
>>   {
>> -	if (!test_kvm_facility(vcpu->kvm, 76))
>> +	/*
>> +	 * If neither the AP instructions nor the MSAX3 facility are installed
>> +	 * on the host, then there is no need for a CRYCB in SIE because they
>> +	 * will not be installed on the guest either.
>> +	 */
>> +	if (!test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_AP) &&
>> +	    !test_facility(76))
> I think this can just stay "test_kvm_facility(vcpu->kvm, 76)", and the
> comment should be changed to
>
> "If neither the AP instructions nor the MSAX3 facility are configured
> for the guest, there is nothing to set up."
>
> Or am I missing something important here?

No, you're not missing anything, it can be test_kvm_facility() and I'm
more than happy to change the comment.

>
> After the CPU has been created, both feature can no longer change. The
> only thing that might change is kvm->arch.crypto.aes_kw/dea_kw but only
> with test_kvm_facility(vcpu->kvm, 76).
>
>>   		return;
>>   
>> +	vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
>>   	vcpu->arch.sie_block->ecb3 &= ~(ECB3_AES | ECB3_DEA);
>>   
>> -	if (vcpu->kvm->arch.crypto.aes_kw)
>> -		vcpu->arch.sie_block->ecb3 |= ECB3_AES;
>> -	if (vcpu->kvm->arch.crypto.dea_kw)
>> -		vcpu->arch.sie_block->ecb3 |= ECB3_DEA;
>> +	vcpu->arch.sie_block->eca &= ~ECA_APIE;
> As this feature can never flip, clearing the flag is not necessary.

Okay.

>
>> +	if (test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_AP))
>> +		vcpu->arch.sie_block->eca |= ECA_APIE;
>>   
>> -	vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
>> +	/* If MSAX3 is installed on the guest, set up protected key support */
>> +	if (test_kvm_facility(vcpu->kvm, 76)) {
>> +		if (vcpu->kvm->arch.crypto.aes_kw)
>> +			vcpu->arch.sie_block->ecb3 |= ECB3_AES;
>> +		if (vcpu->kvm->arch.crypto.dea_kw)
>> +			vcpu->arch.sie_block->ecb3 |= ECB3_DEA;
>> +	}
> As the feature can never change, and aes_kw/dea_kw are only set to 1 in
> case we have test_kvm_facility(vcpu->kvm, 76), this change is not needed.
>
> I think this function can be pretty much left alone. Just add the
> KVM_S390_VM_CPU_FEAT_AP handling.

I disagree, what about the case where the KVM_S390_VM_CPU_FEAT_AP is
configured for the guest but the MSAX3 facility (76) is not?

>
>>   }
>>   
>>   void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu)
>>
>