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SubjectRe: [PATCH v2 02/15] s390: vsie: implement AP support for second level guest
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On 27.02.2018 15:28, Tony Krowiak wrote:
> Set effective masks and CRYCB format in the shadow copy of the
> guest level 2 CRYCB.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
> ---
> arch/s390/include/asm/kvm-ap.h | 2 +
> arch/s390/kvm/kvm-ap.c | 5 +++
> arch/s390/kvm/vsie.c | 71 +++++++++++++++++++++++++++++++++-------
> 3 files changed, 66 insertions(+), 12 deletions(-)
>
> diff --git a/arch/s390/include/asm/kvm-ap.h b/arch/s390/include/asm/kvm-ap.h
> index 4e43117..ef749e7 100644
> --- a/arch/s390/include/asm/kvm-ap.h
> +++ b/arch/s390/include/asm/kvm-ap.h
> @@ -13,4 +13,6 @@
>
> void kvm_ap_set_crycb_format(struct kvm *kvm, __u32 *crycbd);
>
> +int kvm_ap_get_crycb_format(struct kvm *kvm);
> +
> #endif /* _ASM_KVM_AP */
> diff --git a/arch/s390/kvm/kvm-ap.c b/arch/s390/kvm/kvm-ap.c
> index 5305f4c..bafe63b 100644
> --- a/arch/s390/kvm/kvm-ap.c
> +++ b/arch/s390/kvm/kvm-ap.c
> @@ -11,6 +11,11 @@
>
> #include "kvm-s390.h"
>
> +int kvm_ap_get_crycb_format(struct kvm *kvm)
> +{
> + return kvm->arch.crypto.crycbd & CRYCB_FORMAT_MASK;
> +}

Why exactly do we need this function? If there are no other users, just
do it directly in the code below.

> +
> static int kvm_ap_apxa_installed(void)
> {
> int ret;
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index 8961e39..93076ba 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -18,6 +18,7 @@
> #include <asm/sclp.h>
> #include <asm/nmi.h>
> #include <asm/dis.h>
> +#include <asm/kvm-ap.h>
> #include "kvm-s390.h"
> #include "gaccess.h"
>
> @@ -137,12 +138,56 @@ static int prepare_cpuflags(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> }
>
> /*
> + * Set up the effective masks for the shadow copy of the crycb. The effective
> + * masks for guest 3 are set by performing a logical bitwise AND of the guest 3
> + * masks with the guest 2 masks.
> + */
> +static void set_crycb_emasks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> +{
> + int fmt = kvm_ap_get_crycb_format(vcpu->kvm);
> + unsigned long *mask1, *mask2;
> +
> + switch (fmt) {
> + case CRYCB_FORMAT1:
> + case CRYCB_FORMAT2:

Assume L2 gave us FORMAT0 and we are using FORMAT2. You would copy wrong
bits. See below, maybe we need conversion.

> + mask1 = (unsigned long *)vsie_page->crycb.apcb1.apm;
> + mask2 = (unsigned long *)
> + vcpu->kvm->arch.crypto.crycb->apcb1.apm;
> + bitmap_and(mask1, mask1, mask2, APCB1_MASK_SIZE);
> +
> + mask1 = (unsigned long *)vsie_page->crycb.apcb1.aqm;
> + mask2 = (unsigned long *)
> + vcpu->kvm->arch.crypto.crycb->apcb1.aqm;
> + bitmap_and(mask1, mask1, mask2, APCB1_MASK_SIZE);
> +
> + mask1 = (unsigned long *)vsie_page->crycb.apcb1.adm;
> + mask2 = (unsigned long *)
> + vcpu->kvm->arch.crypto.crycb->apcb1.adm;
> + bitmap_and(mask1, mask1, mask2, APCB1_MASK_SIZE);
> + break;
> + default:
> + mask1 = (unsigned long *)vsie_page->crycb.apcb0.apm;
> + mask2 = (unsigned long *)
> + vcpu->kvm->arch.crypto.crycb->apcb1.apm;
> + bitmap_and(mask1, mask1, mask2, APCB0_MASK_SIZE);
> +
> + mask1 = (unsigned long *)vsie_page->crycb.apcb0.aqm;
> + mask2 = (unsigned long *)
> + vcpu->kvm->arch.crypto.crycb->apcb1.aqm;
> + bitmap_and(mask1, mask1, mask2, APCB0_MASK_SIZE);
> +
> + mask1 = (unsigned long *)vsie_page->crycb.apcb0.adm;
> + mask2 = (unsigned long *)
> + vcpu->kvm->arch.crypto.crycb->apcb1.adm;
> + bitmap_and(mask1, mask1, mask2, APCB0_MASK_SIZE);
> + break;
> + }
> +}
> +
> +/*
> * 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
> */
> @@ -155,9 +200,17 @@ 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;
> + scb_s->crycbd = ((__u32)(__u64) &vsie_page->crycb);
> + kvm_ap_set_crycb_format(vcpu->kvm, &scb_s->crycbd);
> +
> + /* copy the crycb */
> + if (read_guest_real(vcpu, crycb_addr, &vsie_page->crycb,
> + sizeof(vsie_page->crycb)))
> + return set_validity_icpt(scb_s, 0x0035U);

This looks wrong. You are always copying from L2, although L2 might not
even set up a crycb for L3. You removed the important crycbd_o check.

Don't we need the following?

a) Determine the _allowed_ crycb format for L2 -> L3. (How can we tell
which format L2 is allowed to use for L3)
b) Determine the target crycb format. This is basically
vm_ap_set_crycb_format afaics.
c) Convert the given crycb to the target crycb format.

So importantly, can you clarify (as I don't have access to documentation):

- When is L2 allowed to use format-0? So when will the format not be
ignored but is actually used?

- When is L2 allowed to use fortma-2? So when will the format not be
ignored but is actually used?

- When does the SIE start interpreting AP instructions? So how can we
hinder it from doing so? Empty masks? crycb format?

> +
> + /* set up the effective masks */
> + set_crycb_emasks(vcpu, vsie_page);
> +
> /* format-1 is supported with message-security-assist extension 3 */
> if (!test_kvm_facility(vcpu->kvm, 76))
> return 0;

You now already copied the wrapping keys. So they could be !0. Please
add a comment why we don't care.

/* wrapping keys are ignored without ECB3_AES / ECB3_DEA */

> @@ -172,13 +225,7 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> 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;
>


--

Thanks,

David / dhildenb

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