[PATCH v2 01/13] KVM: s390: pv: avoid stall notifications for some UVCs

Claudio Imbrenda
2021-07-28T14:27:37Z

Improve make_secure_pte to avoid stalls when the system is heavily
overcommitted. This was especially problematic in kvm_s390_pv_unpack,
because of the loop over all pages that needed unpacking.

Also fix kvm_s390_pv_init_vm to avoid stalls when the system is heavily
overcommitted.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
arch/s390/kernel/uv.c | 11 ++++++++---
arch/s390/kvm/pv.c | 2 +-
2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index aeb0a15bcbb7..fd0faa51c1bb 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -196,11 +196,16 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr,
if (!page_ref_freeze(page, expected))
return -EBUSY;
set_bit(PG_arch_1, &page->flags);
- rc = uv_call(0, (u64)uvcb);
+ rc = __uv_call(0, (u64)uvcb);
page_ref_unfreeze(page, expected);
- /* Return -ENXIO if the page was not mapped, -EINVAL otherwise */
- if (rc)
+ /*
+ * Return -ENXIO if the page was not mapped, -EINVAL for other errors.
+ * If busy or partially completed, return -EAGAIN.
+ */
+ if (rc == 1)
rc = uvcb->rc == 0x10a ? -ENXIO : -EINVAL;
+ else if (rc > 1)
+ rc = -EAGAIN;
return rc;
}

diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index c8841f476e91..e007df11a2fe 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -196,7 +196,7 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
uvcb.conf_base_stor_origin = (u64)kvm->arch.pv.stor_base;
uvcb.conf_virt_stor_origin = (u64)kvm->arch.pv.stor_var;

- cc = uv_call(0, (u64)&uvcb);
+ cc = uv_call_sched(0, (u64)&uvcb);
*rc = uvcb.header.rc;
*rrc = uvcb.header.rrc;
KVM_UV_EVENT(kvm, 3, "PROTVIRT CREATE VM: handle %llx len %llx rc %x rrc %x",
--
2.31.1