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Date: Thu, 10 Feb 2022 10:43:26 +0100
From: Christian Borntraeger <borntraeger@...ux.ibm.com>
To: Janis Schoetterl-Glausch <scgl@...ux.ibm.com>,
Janosch Frank <frankja@...ux.ibm.com>,
Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc: Alexander Gordeev <agordeev@...ux.ibm.com>,
David Hildenbrand <david@...hat.com>,
Jonathan Corbet <corbet@....net>, kvm@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-s390@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
Sven Schnelle <svens@...ux.ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Heiko Carstens <hca@...ux.ibm.com>
Subject: Re: [PATCH v3 05/10] KVM: s390: Add optional storage key checking to
MEMOP IOCTL
Am 10.02.22 um 10:40 schrieb Janis Schoetterl-Glausch:
> On 2/10/22 10:29, Christian Borntraeger wrote:
>> Am 09.02.22 um 18:04 schrieb Janis Schoetterl-Glausch:
>>> User space needs a mechanism to perform key checked accesses when
>>> emulating instructions.
>>>
>>> The key can be passed as an additional argument.
>>> Having an additional argument is flexible, as user space can
>>> pass the guest PSW's key, in order to make an access the same way the
>>> CPU would, or pass another key if necessary.
>>>
>>> Signed-off-by: Janis Schoetterl-Glausch <scgl@...ux.ibm.com>
>>> Acked-by: Janosch Frank <frankja@...ux.ibm.com>
>>> Reviewed-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
>>
>> Claudio, Janosch, can you confirm that this is still valid?
>>
>>
>> Reviewed-by: Christian Borntraeger <borntraeger@...ibm.com>
>
> Not @linux.ibm.com?
Yes, of course. Old habits...
Reviewed-by: Christian Borntraeger <borntraeger@...ux.ibm.com>
>>
>> minor thing below
>>> ---
>>> arch/s390/kvm/kvm-s390.c | 30 ++++++++++++++++++++----------
>>> include/uapi/linux/kvm.h | 6 +++++-
>>> 2 files changed, 25 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>>> index cf347e1a4f17..85763ec7bc60 100644
>>> --- a/arch/s390/kvm/kvm-s390.c
>>> +++ b/arch/s390/kvm/kvm-s390.c
>>> @@ -32,6 +32,7 @@
>>> #include <linux/sched/signal.h>
>>> #include <linux/string.h>
>>> #include <linux/pgtable.h>
>>> +#include <linux/bitfield.h>
>>
>> do we still need that after the changes?
>
> No, not since we moved the key out of the flags.
>>
>>> #include <asm/asm-offsets.h>
>>> #include <asm/lowcore.h>
>>> @@ -2359,6 +2360,11 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
>>> return r;
>>> }
>>> +static bool access_key_invalid(u8 access_key)
>>> +{
>>> + return access_key > 0xf;
>>> +}
>>> +
>>> long kvm_arch_vm_ioctl(struct file *filp,
>>> unsigned int ioctl, unsigned long arg)
>>> {
>>> @@ -4690,17 +4696,19 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
>>> void *tmpbuf = NULL;
>>> int r = 0;
>>> const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION
>>> - | KVM_S390_MEMOP_F_CHECK_ONLY;
>>> + | KVM_S390_MEMOP_F_CHECK_ONLY
>>> + | KVM_S390_MEMOP_F_SKEY_PROTECTION;
>>> if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size)
>>> return -EINVAL;
>>> -
>>> if (mop->size > MEM_OP_MAX_SIZE)
>>> return -E2BIG;
>>> -
>>> if (kvm_s390_pv_cpu_is_protected(vcpu))
>>> return -EINVAL;
>>> -
>>> + if (mop->flags & KVM_S390_MEMOP_F_SKEY_PROTECTION) {
>>> + if (access_key_invalid(mop->key))
>>> + return -EINVAL;
>>> + }
>>> if (!(mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY)) {
>>> tmpbuf = vmalloc(mop->size);
>>> if (!tmpbuf)
>>> @@ -4710,11 +4718,12 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
>>> switch (mop->op) {
>>> case KVM_S390_MEMOP_LOGICAL_READ:
>>> if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) {
>>> - r = check_gva_range(vcpu, mop->gaddr, mop->ar,
>>> - mop->size, GACC_FETCH, 0);
>>> + r = check_gva_range(vcpu, mop->gaddr, mop->ar, mop->size,
>>> + GACC_FETCH, mop->key);
>>> break;
>>> }
>>> - r = read_guest(vcpu, mop->gaddr, mop->ar, tmpbuf, mop->size);
>>> + r = read_guest_with_key(vcpu, mop->gaddr, mop->ar, tmpbuf,
>>> + mop->size, mop->key);
>>> if (r == 0) {
>>> if (copy_to_user(uaddr, tmpbuf, mop->size))
>>> r = -EFAULT;
>>> @@ -4722,15 +4731,16 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
>>> break;
>>> case KVM_S390_MEMOP_LOGICAL_WRITE:
>>> if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) {
>>> - r = check_gva_range(vcpu, mop->gaddr, mop->ar,
>>> - mop->size, GACC_STORE, 0);
>>> + r = check_gva_range(vcpu, mop->gaddr, mop->ar, mop->size,
>>> + GACC_STORE, mop->key);
>>> break;
>>> }
>>> if (copy_from_user(tmpbuf, uaddr, mop->size)) {
>>> r = -EFAULT;
>>> break;
>>> }
>>> - r = write_guest(vcpu, mop->gaddr, mop->ar, tmpbuf, mop->size);
>>> + r = write_guest_with_key(vcpu, mop->gaddr, mop->ar, tmpbuf,
>>> + mop->size, mop->key);
>>> break;
>>> }
>>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>>> index b46bcdb0cab1..44558cf4c52e 100644
>>> --- a/include/uapi/linux/kvm.h
>>> +++ b/include/uapi/linux/kvm.h
>>> @@ -562,7 +562,10 @@ struct kvm_s390_mem_op {
>>> __u32 op; /* type of operation */
>>> __u64 buf; /* buffer in userspace */
>>> union {
>>> - __u8 ar; /* the access register number */
>>> + struct {
>>> + __u8 ar; /* the access register number */
>>> + __u8 key; /* access key, ignored if flag unset */
>>> + };
>>> __u32 sida_offset; /* offset into the sida */
>>> __u8 reserved[32]; /* should be set to 0 */
>>> };
>>> @@ -575,6 +578,7 @@ struct kvm_s390_mem_op {
>>> /* flags for kvm_s390_mem_op->flags */
>>> #define KVM_S390_MEMOP_F_CHECK_ONLY (1ULL << 0)
>>> #define KVM_S390_MEMOP_F_INJECT_EXCEPTION (1ULL << 1)
>>> +#define KVM_S390_MEMOP_F_SKEY_PROTECTION (1ULL << 2)
>>> /* for KVM_INTERRUPT */
>>> struct kvm_interrupt {
>
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