Re: [PATCH v9 20/22] KVM: s390: Handling of Cypto control block in VSIE

[David Hildenbrand <david@redhat.com>]

On 13.08.2018 23:48, Tony Krowiak wrote:
> From: Pierre Morel <pmorel@linux.ibm.com>
> 
> Shadowing the crypto control block now supports APCB shadowing.
> 
> AP instruction interpretation for guest 3 through ECA.28 is shadowed when
> guest 2 ECA.28 is set.
> 
> CRYCB is shadowed for APCB and wrapping keys.
> 
> CRYCB format 0 is now supported for both guests 2 and 3.
> 
> Shadow CRYCB always uses the guest 2 CRYCB format and it
> follows that:
> 
> * Guest 3 CRYCB format 0 is supported with guest 2 CRYCB format 0,1 or 2
> * Guest 3 CRYCB format 1 is supported with guest 2 CRYCB format 1 or 2
> * Guest 3 CRYCB format 2 is supported with guest 2 CRYCB format 2
> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> Acked-by: Halil Pasic <pasic@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/kvm/vsie.c |  222 ++++++++++++++++++++++++++++++++++++++++++++------
>  1 files changed, 198 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index aa30b48..e15240e 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -136,17 +136,8 @@ static int prepare_cpuflags(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>  	return 0;
>  }
>  
> -/*
> - * Create a shadow copy of the crycb block and setup key wrapping, if
> - * requested for guest 3 and enabled for guest 2.
> - *
> - * We only accept format-1 (no AP in g2), but convert it into format-2
> - * There is nothing to do for format-0.
> - *
> - * Returns: - 0 if shadowed or nothing to do
> - *          - > 0 if control has to be given to guest 2
> - */
> -static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> +/* Copy keys into shadow crycb, is only called if MSA3 is available.  */
> +static int copy_key_masks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>  {
>  	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
>  	struct kvm_s390_sie_block *scb_o = vsie_page->scb_o;
> @@ -155,30 +146,17 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>  	unsigned long *b1, *b2;
>  	u8 ecb3_flags;
>  
> -	scb_s->crycbd = 0;
> -	if (!(crycbd_o & vcpu->arch.sie_block->crycbd & CRYCB_FORMAT1))
> -		return 0;
> -	/* format-1 is supported with message-security-assist extension 3 */
> -	if (!test_kvm_facility(vcpu->kvm, 76))
> -		return 0;
>  	/* we may only allow it if enabled for guest 2 */
>  	ecb3_flags = scb_o->ecb3 & vcpu->arch.sie_block->ecb3 &
>  		     (ECB3_AES | ECB3_DEA);
>  	if (!ecb3_flags)
>  		return 0;
>  
> -	if ((crycb_addr & PAGE_MASK) != ((crycb_addr + 128) & PAGE_MASK))
> -		return set_validity_icpt(scb_s, 0x003CU);
> -	else if (!crycb_addr)
> -		return set_validity_icpt(scb_s, 0x0039U);
> -
>  	/* copy only the wrapping keys */
>  	if (read_guest_real(vcpu, crycb_addr + 72, &vsie_page->crycb, 56))
>  		return set_validity_icpt(scb_s, 0x0035U);
>  
>  	scb_s->ecb3 |= ecb3_flags;
> -	scb_s->crycbd = ((__u32)(__u64) &vsie_page->crycb) | CRYCB_FORMAT1 |
> -			CRYCB_FORMAT2;
>  
>  	/* xor both blocks in one run */
>  	b1 = (unsigned long *) vsie_page->crycb.dea_wrapping_key_mask;
> @@ -189,6 +167,202 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>  	return 0;
>  }
>  
> +/* Copy masks into apcb when g2 and g3 use format 1 */
> +static int copy_apcb1(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> +{
> +	struct kvm_s390_sie_block *scb_o = vsie_page->scb_o;
> +	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
> +	const uint32_t crycbd_o = READ_ONCE(scb_o->crycbd);
> +	const u32 crycb_o = crycbd_o & 0x7ffffff8U;

Can you pass crycb_o instead please to all applicable users from the
initial handler? Otherwise the READ_ONCE() is of no use any more.

> +	struct kvm_s390_crypto_cb *crycb_h = &vcpu->kvm->arch.sie_page2->crycb;
> +	struct kvm_s390_crypto_cb *crycb_s = &vsie_page->crycb;
> +	unsigned long *apcb_s = (unsigned long *) &crycb_s->apcb1;
> +	unsigned long *apcb_h = (unsigned long *) &crycb_h->apcb1;
> +	int i;
> +	u32 src;
> +
> +	src = crycb_o + offsetof(struct kvm_s390_crypto_cb, apcb1);
> +	if (read_guest_real(vcpu, src, apcb_s, sizeof(struct kvm_s390_apcb1)))

can you instead return -EFAULT and handle 0035U for all cases in the caller?

So you might be able to not pass vsie_page in here.

Same applies to the other handlers below. (and also above)

> +		return set_validity_icpt(scb_s, 0x0035U);
> +
> +	for (i = 0; i < sizeof(struct kvm_s390_apcb1); i += sizeof(*apcb_s))
> +		*apcb_s &= *apcb_h;
> +
> +	return 0;
> +}
> +
> +/*
> + * Copy masks into apcb when g2 use format 1 and g3 use format 0
> + * In this case the shadow APCB uses format 1
> + */
> +static int copy_apcb01(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> +{
> +	struct kvm_s390_sie_block *scb_o = vsie_page->scb_o;
> +	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
> +	const uint32_t crycbd_o = READ_ONCE(scb_o->crycbd);
> +	const u32 crycb_o = crycbd_o & 0x7ffffff8U;
> +	struct kvm_s390_apcb1 *apcb_h = &vcpu->kvm->arch.sie_page2->crycb.apcb1;
> +	struct kvm_s390_apcb1 *apcb_s = &vsie_page->crycb.apcb1;
> +	u32 src;
> +
> +	memset(apcb_s, 0, sizeof(*apcb_s));
> +
> +	src = crycb_o + offsetof(struct kvm_s390_crypto_cb, apcb0.apm[0]);
> +	if (read_guest_real(vcpu, src, &apcb_s->apm[0], sizeof(__u64)))
> +		return set_validity_icpt(scb_s, 0x0035U);
> +
> +	src = crycb_o + offsetof(struct kvm_s390_crypto_cb, apcb0.aqm[0]);
> +	if (read_guest_real(vcpu, src, &apcb_s->aqm[0], sizeof(__u64)))
> +		return set_validity_icpt(scb_s, 0x0035U);
> +
> +	src = crycb_o + offsetof(struct kvm_s390_crypto_cb, apcb0.adm[0]);
> +	if (read_guest_real(vcpu, src, &apcb_s->adm[0], sizeof(__u64)))
> +		return set_validity_icpt(scb_s, 0x0035U);
> +
> +	apcb_s->apm[0] &= apcb_h->apm[0];
> +	apcb_s->aqm[0] &= apcb_h->aqm[0];
> +	apcb_s->adm[0] &= apcb_h->adm[0];
> +
> +	return 0;
> +}
> +
> +/* Copy masks into apcb when g2 and g3 use format 0 */
> +static int copy_apcb0(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> +{
> +	struct kvm_s390_sie_block *scb_o = vsie_page->scb_o;
> +	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
> +	const uint32_t crycbd_o = READ_ONCE(scb_o->crycbd);
> +	const u32 crycb_o = crycbd_o & 0x7ffffff8U;
> +	struct kvm_s390_apcb0 *apcb_h = &vcpu->kvm->arch.sie_page2->crycb.apcb0;
> +	struct kvm_s390_apcb0 *apcb_s = &vsie_page->crycb.apcb0;
> +	u32 src;
> +
> +	src = crycb_o + offsetof(struct kvm_s390_crypto_cb, apcb0.apm[0]);
> +	if (read_guest_real(vcpu, src, &apcb_s->apm[0], sizeof(__u64)))
> +		return set_validity_icpt(scb_s, 0x0035U);
> +
> +	src = crycb_o + offsetof(struct kvm_s390_crypto_cb, apcb0.aqm[0]);
> +	if (read_guest_real(vcpu, src, &apcb_s->aqm[0], sizeof(__u64)))
> +		return set_validity_icpt(scb_s, 0x0035U);
> +
> +	src = crycb_o + offsetof(struct kvm_s390_crypto_cb, apcb0.adm[0]);
> +	if (read_guest_real(vcpu, src, &apcb_s->adm[0], sizeof(__u64)))
> +		return set_validity_icpt(scb_s, 0x0035U);
> +
> +	apcb_s->apm[0] &= apcb_h->apm[0];
> +	apcb_s->aqm[0] &= apcb_h->aqm[0];
> +	apcb_s->adm[0] &= apcb_h->adm[0];
> +
> +	return 0;
> +}
> +
> +/* Shadowing APCB depends on G2 and G3 CRYCB format */
> +static int copy_apcb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
> +		     int g2_fmt, int g3_fmt)
> +{
> +	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
> +	int ret = 0;
> +
> +	switch (g2_fmt) {
> +	case CRYCB_FORMAT0:
> +		switch (g3_fmt) {
> +		case  CRYCB_FORMAT0:
> +			ret = copy_apcb0(vcpu, vsie_page);
> +			break;
> +		default:
> +			return set_validity_icpt(scb_s, 0x0020U);

return -EINVAL and handle it in the caller (like I suggested with -EFAULT).

Try to not pass vsie_page down here. (same applies to copy_key_masks())

> +		}
> +		break;
> +	case CRYCB_FORMAT1:
> +		switch (g3_fmt) {
> +		case CRYCB_FORMAT1:
> +		case CRYCB_FORMAT0:	/* Fall through to copy APCB */
> +			ret = copy_apcb0(vcpu, vsie_page);
> +			break;
> +		default:
> +			return set_validity_icpt(scb_s, 0x0020U);
> +		}
> +		break;
> +	case CRYCB_FORMAT2:
> +		switch (g3_fmt) {
> +		case CRYCB_FORMAT0:
> +		case CRYCB_FORMAT1:
> +			ret = copy_apcb01(vcpu, vsie_page);
> +			break;
> +		case CRYCB_FORMAT2:
> +			ret = copy_apcb1(vcpu, vsie_page);
> +			break;
> +		}
> +		break;
> +	default:
> +	/*
> +	 * Guest 2 format is valid or we can not get to here.
> +	 */
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +/*
> + * Create a shadow copy of the crycb block.
> + * - Setup key wrapping, if requested for guest 3 and enabled for guest 2.
> + * - Shadow APCB if requested by guest 3 and enabled for guest 2 through
> + *   ECA_APIE.
> + *
> + * We only accept format-1 (no AP in g2), but convert it into format-2
> + * There is nothing to do for format-0.
> + *
> + * Returns: - 0 if shadowed or nothing to do
> + *          - > 0 if control has to be given to guest 2
> + *          - < 0 if something went wrong on copy
> + */
> +static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> +{
> +	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
> +	struct kvm_s390_sie_block *scb_o = vsie_page->scb_o;
> +	const uint32_t crycbd_o = READ_ONCE(scb_o->crycbd);
> +	const u32 crycb_addr = crycbd_o & 0x7ffffff8U;
> +	int g2_fmt = vcpu->arch.sie_block->crycbd & CRYCB_FORMAT_MASK;
> +	int g3_fmt = crycbd_o & CRYCB_FORMAT_MASK;

you can make these two const, too.

> +	int g2_apie, g2_msa3, g3_apie, g3_msa3;

you can initialize these all directly and make them const.

> +	int size, ret;
> +
> +	/* crycb should not cross a page boundary */
> +	size = (g3_fmt == CRYCB_FORMAT2) ? 0x100 : 0x80;
> +	if ((crycb_addr & PAGE_MASK) != ((crycb_addr + size) & PAGE_MASK))
> +		return set_validity_icpt(scb_s, 0x003CU);

You are changing the order of checks compared to existing code. E.g. if
we will not be using the crycbo (as !g3_apie and !g3_msa3), you are
still injecting a validity - existing code won't do that.

Also, you would allow to accept a CRYCB_FORMAT2 here (and perform a
check) although the emulated machine might not even be aware of that
(e.g. !g2_apie and ! g2_msa3)

I don't like such subtle changes. If existing code is wrong, please fix
it first (and explain why it is the right thing to do) or stick to
existing handling as close as possible. Not having access to the
documentation makes me rely on the existing code (and assume it is correct).

> +
> +	g2_apie = vcpu->arch.sie_block->eca & ECA_APIE;
> +	g3_apie = scb_o->eca & g2_apie;
> +
> +	g2_msa3 = test_kvm_facility(vcpu->kvm, 76);
> +	g3_msa3 = (g3_fmt != CRYCB_FORMAT0) & g2_msa3;

We should also consider (ECB3_AES | ECB3_DEA) here. because if both are
not set, there is logically no g3_msa3. (existing code does that)

> +
> +	scb_s->crycbd = 0;
> +	/* If no AP instructions and no keys we just set crycbd to 0 */
> +	if (!(g3_apie || g3_msa3))
> +		return 0;
> +
> +	if (!crycb_addr)
> +		return set_validity_icpt(scb_s, 0x0039U);
> +
> +	if (g3_apie) {
> +		ret = copy_apcb(vcpu, vsie_page, g2_fmt, g3_fmt);
> +		if (ret)
> +			return ret;
> +		scb_s->eca |= g3_apie;
> +	}
> +
> +	if (g3_msa3)
> +		ret = copy_key_masks(vcpu, vsie_page);
> +
> +	if (!ret)
> +		scb_s->crycbd = ((__u32)(__u64) &vsie_page->crycb) | g2_fmt;
> +
> +	return ret;
> +}
> +
>  /* shadow (round up/down) the ibc to avoid validity icpt */
>  static void prepare_ibc(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>  {
> 


-- 

Thanks,

David / dhildenb