[PATCH v5 02/13] KVM: s390: refactor crypto initialization

[Tony Krowiak]

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 as long as the
AP instructions are installed on the host.

Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx>
---
 arch/s390/include/asm/kvm_host.h |    1 +
 arch/s390/kvm/kvm-s390.c         |   64 ++++++++++++++++++++++++++-----------
 2 files changed, 46 insertions(+), 19 deletions(-)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 81cdb6b..5393c4d 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -255,6 +255,7 @@ 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/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 1f50de7..99779a6 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1875,14 +1875,35 @@ long kvm_arch_vm_ioctl(struct file *filp,
 	return r;
 }
 
-static void kvm_s390_set_crycb_format(struct kvm *kvm)
+/*
+ * 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_format_crycb(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_ap_apxa_installed())
 		kvm->arch.crypto.crycbd |= CRYCB_FORMAT2;
 	else
 		kvm->arch.crypto.crycbd |= CRYCB_FORMAT1;
+
+	/* Enable AES/DEA protected key functions by default */
+	kvm->arch.crypto.aes_kw = 1;
+	kvm->arch.crypto.dea_kw = 1;
+	get_random_bytes(kvm->arch.crypto.crycb->aes_wrapping_key_mask,
+			 sizeof(kvm->arch.crypto.crycb->aes_wrapping_key_mask));
+	get_random_bytes(kvm->arch.crypto.crycb->dea_wrapping_key_mask,
+			 sizeof(kvm->arch.crypto.crycb->dea_wrapping_key_mask));
 }
 
 static u64 kvm_s390_get_initial_cpuid(void)
@@ -1896,19 +1917,17 @@ static u64 kvm_s390_get_initial_cpuid(void)
 
 static void kvm_s390_crypto_init(struct kvm *kvm)
 {
-	if (!test_kvm_facility(kvm, 76))
+	/*
+	 * If neither the AP instructions nor the message security assist
+	 * extension 3 (MSAX3) are installed, there is no need to initialize a
+	 * crypto control block (CRYCB) for the guest.
+	 */
+	if (!kvm_ap_instructions_available() && !test_kvm_facility(kvm, 76))
 		return;
 
 	kvm->arch.crypto.crycb = &kvm->arch.sie_page2->crycb;
-	kvm_s390_set_crycb_format(kvm);
-
-	/* Enable AES/DEA protected key functions by default */
-	kvm->arch.crypto.aes_kw = 1;
-	kvm->arch.crypto.dea_kw = 1;
-	get_random_bytes(kvm->arch.crypto.crycb->aes_wrapping_key_mask,
-			 sizeof(kvm->arch.crypto.crycb->aes_wrapping_key_mask));
-	get_random_bytes(kvm->arch.crypto.crycb->dea_wrapping_key_mask,
-			 sizeof(kvm->arch.crypto.crycb->dea_wrapping_key_mask));
+	kvm->arch.crypto.crycbd = (__u32)(unsigned long) kvm->arch.crypto.crycb;
+	kvm_s390_format_crycb(kvm);
 }
 
 static void sca_dispose(struct kvm *kvm)
@@ -2430,17 +2449,24 @@ 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 a crypto control block designation (CRYCBD) has not been
+	 * initialized
+	 */
+	if (vcpu->kvm->arch.crypto.crycbd == 0)
 		return;
 
-	vcpu->arch.sie_block->ecb3 &= ~(ECB3_AES | ECB3_DEA);
+	vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
 
-	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;
+	/* If MSAX3 is installed, set up protected key support */
+	if (test_kvm_facility(vcpu->kvm, 76)) {
+		vcpu->arch.sie_block->ecb3 &= ~(ECB3_AES | ECB3_DEA);
 
-	vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
+		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;
+	}
 }
 
 void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu)
-- 
1.7.1