Re: [PATCH v4 03/15] KVM: s390: refactor crypto initialization

Tony Krowiak
2018-04-17T14:15:53Z

On 04/16/2018 04:56 AM, Pierre Morel wrote:
> On 15/04/2018 23:22, Tony Krowiak wrote:
>> This patch refactors the code that initializes the crypto
>> configuration for a guest. The crypto configuration is contained in
>> a crypto control block (CRYCB) which is a satellite control block to
>> our main hardware virtualization control block. The CRYCB is
>> attached to the main virtualization control block via a CRYCB
>> designation (CRYCBD) designation field containing the address of
>> the CRYCB as well as its format.
>>
>> Prior to the introduction of AP device virtualization, there was
>> no need to provide access to or specify the format of the CRYCB for
>> a guest unless the MSA extension 3 (MSAX3) facility was installed
>> on the host system. With the introduction of AP device virtualization,
>> the CRYCB and its format must be made accessible to the guest
>> regardless of the presence of the MSAX3 facility.
>>
>> The crypto initialization code is restructured as follows:
>>
>> * A new compilation unit is introduced to contain all interfaces
>> and data structures related to configuring a guest's CRYCB for
>> both the refactoring of crypto initialization as well as all
>> subsequent patches introducing AP virtualization support.
>>
>> * Currently, the asm code for querying the AP configuration is
>> duplicated in the AP bus as well as in KVM. Since the KVM
>> code was introduced, the AP bus has externalized the interface
>> for querying the AP configuration. The KVM interface will be
>> replaced with a call to the AP bus interface. Of course, this
>> will be moved to the new compilation unit mentioned above.
>>
>> * An interface to format the CRYCBD field will be provided via
>> the new compilation unit and called from the KVM vm
>> initialization.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
>> ---
>> arch/s390/include/asm/kvm-ap.h | 15 +++++++++
>> arch/s390/include/asm/kvm_host.h | 1 +
>> arch/s390/kvm/kvm-ap.c | 39 ++++++++++++++++++++++++
>> arch/s390/kvm/kvm-s390.c | 60
>> ++++----------------------------------
>> 4 files changed, 61 insertions(+), 54 deletions(-)
>>
>> diff --git a/arch/s390/include/asm/kvm-ap.h
>> b/arch/s390/include/asm/kvm-ap.h
>> index 84412a9..736e93e 100644
>> --- a/arch/s390/include/asm/kvm-ap.h
>> +++ b/arch/s390/include/asm/kvm-ap.h
>> @@ -10,6 +10,9 @@
>> #ifndef _ASM_KVM_AP
>> #define _ASM_KVM_AP
>>
>> +#include <linux/types.h>
>> +#include <linux/kvm_host.h>
>> +
>> /**
>> * kvm_ap_instructions_installed()
>> *
>> @@ -20,4 +23,16 @@
>> */
>> int kvm_ap_instructions_installed(void);
>>
>> +/**
>> + * kvm_ap_build_crycbd
>> + *
>> + * The crypto control block designation (CRYCBD) is a 32-bit field that
>> + * designates both the host real address and format of the CRYCB.
>> This function
>> + * builds the CRYCBD field for use by the KVM guest.
>> + *
>> + * @kvm: the KVM guest
>> + * @crycbd: reference to the CRYCBD
>> + */
>> +void kvm_ap_build_crycbd(struct kvm *kvm);
>> +
>> #endif /* _ASM_KVM_AP */
>> diff --git a/arch/s390/include/asm/kvm_host.h
>> b/arch/s390/include/asm/kvm_host.h
>> index 81cdb6b..c990a1d 100644
>> --- a/arch/s390/include/asm/kvm_host.h
>> +++ b/arch/s390/include/asm/kvm_host.h
>> @@ -257,6 +257,7 @@ struct kvm_s390_sie_block {
>> __u8 reservedf0[12]; /* 0x00f0 */
>> #define CRYCB_FORMAT1 0x00000001
>> #define CRYCB_FORMAT2 0x00000003
>> +#define CRYCB_FORMAT_MASK 0x00000003
>> __u32 crycbd; /* 0x00fc */
>> __u64 gcr[16]; /* 0x0100 */
>> __u64 gbea; /* 0x0180 */
>> diff --git a/arch/s390/kvm/kvm-ap.c b/arch/s390/kvm/kvm-ap.c
>> index 1267588..991bae4 100644
>> --- a/arch/s390/kvm/kvm-ap.c
>> +++ b/arch/s390/kvm/kvm-ap.c
>> @@ -10,6 +10,8 @@
>> #include <asm/kvm-ap.h>
>> #include <asm/ap.h>
>>
>> +#include "kvm-s390.h"
>> +
>> int kvm_ap_instructions_installed(void)
>> {
>> #ifdef CONFIG_ZCRYPT
>> @@ -19,3 +21,40 @@ int kvm_ap_instructions_installed(void)
>> #endif
>> }
>> EXPORT_SYMBOL(kvm_ap_instructions_installed);
>> +
>> +static inline int kvm_ap_query_config(struct ap_config_info *config)
>> +{
>> + memset(config, 0, sizeof(*config));
>> +
>> +#ifdef CONFIG_ZCRYPT
>
> I would prefer that you define the interface in an include file
> with stubs for the case ZCRYPT is not set.

This is a static function only called internally, but I suppose there is
no harm in defining it as an interface in kvm-ap.h ... it may come
in handy down the road.

>
>
>> + if (kvm_ap_instructions_installed())
>> + return ap_query_configuration(config);
>> +#endif
>> +
>> + return -EOPNOTSUPP;
>> +}
>> +
>> +static int kvm_ap_apxa_installed(void)
>> +{
>> + struct ap_config_info config;
>> +
>> + if (kvm_ap_query_config(&config) == 0)
>> + return (config.apxa == 1);
>> +
>> + return 0;
>> +}
>> +
>> +void kvm_ap_build_crycbd(struct kvm *kvm)
>> +{
>> + kvm->arch.crypto.crycbd = (__u32)(unsigned long)
>> kvm->arch.crypto.crycb;
>> + kvm->arch.crypto.crycbd &= ~(CRYCB_FORMAT_MASK);
>> +
>> + /* check whether MSAX3 is installed */
>
> It means we do not support AP virtualization without MSA3.
> It follows we do not support CRYCB_FORMAT0

If MSAX3 is not installed, that means there is no key wrapping support,
hence CRYCB_FORMAT0. The CRYCB_FORMAT1 and CRYCB_FORMAT2 CRYCBs
both include wrapping key masks. I don't follow your logic here.

>
>
> It is different from what you explain in the comment.

How is it different? Above, we are setting the CRYCBD value regardless
of whether MSAX3 is installed or not. Previously, the CRYCBD value
was set only if MSAX3 is installed (see comments below)

>
>
>> + if (kvm_ap_instructions_installed() && test_kvm_facility(kvm,
>> 76)) {
>> + if (kvm_ap_apxa_installed())
>> + kvm->arch.crypto.crycbd |= CRYCB_FORMAT2;
>> + else
>> + kvm->arch.crypto.crycbd |= CRYCB_FORMAT1;
>> + }
>> +}
>> +EXPORT_SYMBOL(kvm_ap_build_crycbd);
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index d0c3518..b47ff11 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/kvm-ap.h>
>> #include "kvm-s390.h"
>> #include "gaccess.h"
>>
>> @@ -1881,55 +1882,6 @@ 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;
>> -
>> - 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;
>> - }
>> -
>> - return 0;
>> -}
>> -
>> -static void kvm_s390_set_crycb_format(struct kvm *kvm)
>> -{
>> - kvm->arch.crypto.crycbd = (__u32)(unsigned long)
>> kvm->arch.crypto.crycb;
>> -
>> - if (kvm_s390_apxa_installed())
>> - kvm->arch.crypto.crycbd |= CRYCB_FORMAT2;
>> - else
>> - kvm->arch.crypto.crycbd |= CRYCB_FORMAT1;
>> -}
>> -
>> static u64 kvm_s390_get_initial_cpuid(void)
>> {
>> struct cpuid cpuid;
>> @@ -1941,12 +1893,12 @@ static u64 kvm_s390_get_initial_cpuid(void)
>>
>> static void kvm_s390_crypto_init(struct kvm *kvm)
>> {
>> + kvm->arch.crypto.crycb = &kvm->arch.sie_page2->crycb;
>> + kvm_ap_build_crycbd(kvm);
>> +

Notice the call to kvm_ap_build_crycbd(kvm) above was added, so
the CRYCBD is being set regardless of the presence of MSAX3.

>> if (!test_kvm_facility(kvm, 76))
>> return;
>>
>> - kvm->arch.crypto.crycb = &kvm->arch.sie_page2->crycb;
>> - kvm_s390_set_crycb_format(kvm);
Notice that this code that was removed to set the CRYCBD is called
only if MSAX3 is not installed - i.e., see the if statement
immediately preceding the two statements above.
>> -
>> /* Enable AES/DEA protected key functions by default */
>> kvm->arch.crypto.aes_kw = 1;
>> kvm->arch.crypto.dea_kw = 1;
>> @@ -2475,6 +2427,8 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu
>> *vcpu)
>>
>> static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu)
>> {
>> + vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
>> +
>> if (!test_kvm_facility(vcpu->kvm, 76))
>> return;
>>
>> @@ -2484,8 +2438,6 @@ static void kvm_s390_vcpu_crypto_setup(struct
>> kvm_vcpu *vcpu)
>> 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->crycbd = vcpu->kvm->arch.crypto.crycbd;
>> }
>>
>> void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu)
>
>