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Date: Tue, 18 Jan 2022 10:52:06 +0100
From: Janis Schoetterl-Glausch <scgl@...ux.ibm.com>
To: Christian Borntraeger <borntraeger@...ux.ibm.com>,
Janosch Frank <frankja@...ux.ibm.com>,
Heiko Carstens <hca@...ux.ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>
Cc: Janis Schoetterl-Glausch <scgl@...ux.ibm.com>,
David Hildenbrand <david@...hat.com>,
Claudio Imbrenda <imbrenda@...ux.ibm.com>,
Alexander Gordeev <agordeev@...ux.ibm.com>,
kvm@...r.kernel.org, linux-s390@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH v1 06/10] KVM: s390: Add vm IOCTL for key checked guest absolute memory access
Channel I/O honors storage keys and is performed on absolute memory.
For I/O emulation user space therefore needs to be able to do key
checked accesses.
The vm IOCTL supports read/write accesses, as well as checking
if an access would succeed.
Signed-off-by: Janis Schoetterl-Glausch <scgl@...ux.ibm.com>
Acked-by: Janosch Frank <frankja@...ux.ibm.com>
---
arch/s390/kvm/gaccess.c | 72 +++++++++++++++++++++++++++++++++++
arch/s390/kvm/gaccess.h | 6 +++
arch/s390/kvm/kvm-s390.c | 81 ++++++++++++++++++++++++++++++++++++++++
include/uapi/linux/kvm.h | 2 +
4 files changed, 161 insertions(+)
diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index efe33cda38b6..db1d9a494f77 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -795,6 +795,35 @@ static int low_address_protection_enabled(struct kvm_vcpu *vcpu,
return 1;
}
+static int vm_check_access_key(struct kvm *kvm, char access_key,
+ enum gacc_mode mode, gpa_t gpa)
+{
+ unsigned long hva;
+ unsigned char storage_key, access_control;
+ bool fetch_protected;
+ int r;
+
+ if (access_key == 0)
+ return 0;
+
+ hva = gfn_to_hva(kvm, gpa_to_gfn(gpa));
+ if (kvm_is_error_hva(hva))
+ return PGM_ADDRESSING;
+
+ mmap_read_lock(current->mm);
+ r = get_guest_storage_key(current->mm, hva, &storage_key);
+ mmap_read_unlock(current->mm);
+ if (r)
+ return r;
+ access_control = FIELD_GET(_PAGE_ACC_BITS, storage_key);
+ if (access_control == access_key)
+ return 0;
+ fetch_protected = storage_key & _PAGE_FP_BIT;
+ if ((mode == GACC_FETCH || mode == GACC_IFETCH) && !fetch_protected)
+ return 0;
+ return PGM_PROTECTION;
+}
+
static bool fetch_prot_override_applicable(struct kvm_vcpu *vcpu, enum gacc_mode mode,
union asce asce)
{
@@ -990,6 +1019,26 @@ access_guest_page_with_key(struct kvm *kvm, enum gacc_mode mode, gpa_t gpa,
return 0;
}
+int access_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, void *data,
+ unsigned long len, enum gacc_mode mode, char key)
+{
+ int offset = offset_in_page(gpa);
+ int fragment_len;
+ int rc;
+
+ while (min(PAGE_SIZE - offset, len) > 0) {
+ fragment_len = min(PAGE_SIZE - offset, len);
+ rc = access_guest_page_with_key(kvm, mode, gpa, data, fragment_len, key);
+ if (rc)
+ return rc;
+ offset = 0;
+ len -= fragment_len;
+ data += fragment_len;
+ gpa += fragment_len;
+ }
+ return 0;
+}
+
int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
void *data, unsigned long len, enum gacc_mode mode,
char access_key)
@@ -1131,6 +1180,29 @@ int check_gva_range(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar,
return rc;
}
+/**
+ * check_gpa_range - test a range of guest physical addresses for accessibility
+ * @kvm: virtual machine instance
+ * @gpa: guest physical address
+ * @length: length of test range
+ * @mode: access mode to test, relevant for storage keys
+ * @access_key: access key to mach the storage keys with
+ */
+int check_gpa_range(struct kvm *kvm, unsigned long gpa, unsigned long length,
+ enum gacc_mode mode, char access_key)
+{
+ unsigned int fragment_len;
+ int rc = 0;
+
+ while (length && !rc) {
+ fragment_len = min(PAGE_SIZE - offset_in_page(gpa), length);
+ rc = vm_check_access_key(kvm, access_key, mode, gpa);
+ length -= fragment_len;
+ gpa += fragment_len;
+ }
+ return rc;
+}
+
/**
* kvm_s390_check_low_addr_prot_real - check for low-address protection
* @vcpu: virtual cpu
diff --git a/arch/s390/kvm/gaccess.h b/arch/s390/kvm/gaccess.h
index 0d4416178bb6..d89178b92d51 100644
--- a/arch/s390/kvm/gaccess.h
+++ b/arch/s390/kvm/gaccess.h
@@ -194,6 +194,12 @@ int check_gva_range(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar,
unsigned long length, enum gacc_mode mode,
char access_key);
+int check_gpa_range(struct kvm *kvm, unsigned long gpa, unsigned long length,
+ enum gacc_mode mode, char access_key);
+
+int access_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, void *data,
+ unsigned long len, enum gacc_mode mode, char key);
+
int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
void *data, unsigned long len, enum gacc_mode mode,
char access_key);
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c4acdb025ff1..8dab956f84a6 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2390,6 +2390,78 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
return r;
}
+static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
+{
+ static const __u8 zeros[sizeof(mop->reserved)] = {0};
+ void __user *uaddr = (void __user *)mop->buf;
+ u64 supported_flags;
+ void *tmpbuf = NULL;
+ char access_key;
+ int r, srcu_idx;
+
+ access_key = FIELD_GET(KVM_S390_MEMOP_F_SKEYS_ACC, mop->flags);
+ supported_flags = KVM_S390_MEMOP_F_SKEYS_ACC
+ | KVM_S390_MEMOP_F_CHECK_ONLY;
+ if (mop->flags & ~supported_flags)
+ return -EINVAL;
+ if (mop->size > MEM_OP_MAX_SIZE)
+ return -E2BIG;
+ if (kvm_s390_pv_is_protected(kvm))
+ return -EINVAL;
+ if (memcmp(mop->reserved, zeros, sizeof(zeros)) != 0)
+ return -EINVAL;
+
+ if (!(mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY)) {
+ tmpbuf = vmalloc(mop->size);
+ if (!tmpbuf)
+ return -ENOMEM;
+ }
+
+ srcu_idx = srcu_read_lock(&kvm->srcu);
+
+ if (kvm_is_error_gpa(kvm, mop->gaddr)) {
+ r = PGM_ADDRESSING;
+ goto out_unlock;
+ }
+
+ switch (mop->op) {
+ case KVM_S390_MEMOP_ABSOLUTE_READ: {
+ if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) {
+ r = check_gpa_range(kvm, mop->gaddr, mop->size, GACC_FETCH, access_key);
+ } else {
+ r = access_guest_abs_with_key(kvm, mop->gaddr, tmpbuf,
+ mop->size, GACC_FETCH, access_key);
+ if (r == 0) {
+ if (copy_to_user(uaddr, tmpbuf, mop->size))
+ r = -EFAULT;
+ }
+ }
+ break;
+ }
+ case KVM_S390_MEMOP_ABSOLUTE_WRITE: {
+ if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) {
+ r = check_gpa_range(kvm, mop->gaddr, mop->size, GACC_STORE, access_key);
+ } else {
+ if (copy_from_user(tmpbuf, uaddr, mop->size)) {
+ r = -EFAULT;
+ break;
+ }
+ r = access_guest_abs_with_key(kvm, mop->gaddr, tmpbuf,
+ mop->size, GACC_STORE, access_key);
+ }
+ break;
+ }
+ default:
+ r = -EINVAL;
+ }
+
+out_unlock:
+ srcu_read_unlock(&kvm->srcu, srcu_idx);
+
+ vfree(tmpbuf);
+ return r;
+}
+
long kvm_arch_vm_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
@@ -2514,6 +2586,15 @@ long kvm_arch_vm_ioctl(struct file *filp,
}
break;
}
+ case KVM_S390_MEM_OP: {
+ struct kvm_s390_mem_op mem_op;
+
+ if (copy_from_user(&mem_op, argp, sizeof(mem_op)) == 0)
+ r = kvm_s390_vm_mem_op(kvm, &mem_op);
+ else
+ r = -EFAULT;
+ break;
+ }
default:
r = -ENOTTY;
}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index e3f450b2f346..dd04170287fd 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -572,6 +572,8 @@ struct kvm_s390_mem_op {
#define KVM_S390_MEMOP_LOGICAL_WRITE 1
#define KVM_S390_MEMOP_SIDA_READ 2
#define KVM_S390_MEMOP_SIDA_WRITE 3
+#define KVM_S390_MEMOP_ABSOLUTE_READ 4
+#define KVM_S390_MEMOP_ABSOLUTE_WRITE 5
/* 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)
--
2.32.0
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