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Wed, 4 Aug 2021 15:40:54 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 057954C075; Wed, 4 Aug 2021 15:40:54 +0000 (GMT) Received: from localhost.localdomain (unknown [9.145.2.150]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 4 Aug 2021 15:40:53 +0000 (GMT) From: Claudio Imbrenda To: kvm@vger.kernel.org Cc: cohuck@redhat.com, borntraeger@de.ibm.com, frankja@linux.ibm.com, thuth@redhat.com, pasic@linux.ibm.com, david@redhat.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Ulrich.Weigand@de.ibm.com Subject: [PATCH v3 02/14] KVM: s390: pv: avoid stall notifications for some UVCs Date: Wed, 4 Aug 2021 17:40:34 +0200 Message-Id: <20210804154046.88552-3-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210804154046.88552-1-imbrenda@linux.ibm.com> References: <20210804154046.88552-1-imbrenda@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: P4iwglZWaB-ebKDoSOk2lpFgQvVwSk5w X-Proofpoint-ORIG-GUID: d4itgAOjKDi4UR_BWN6GP-Xfpnnw6Qwx X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-04_03:2021-08-04,2021-08-04 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 adultscore=0 impostorscore=0 clxscore=1015 mlxscore=0 malwarescore=0 suspectscore=0 priorityscore=1501 phishscore=0 spamscore=0 mlxlogscore=999 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108040089 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Fixes: 214d9bbcd3a672 ("s390/mm: provide memory management functions for protected KVM guests") --- arch/s390/kernel/uv.c | 29 +++++++++++++++++++++++------ arch/s390/kvm/pv.c | 2 +- 2 files changed, 24 insertions(+), 7 deletions(-) diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c index aeb0a15bcbb7..68a8fbafcb9c 100644 --- a/arch/s390/kernel/uv.c +++ b/arch/s390/kernel/uv.c @@ -180,7 +180,7 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr, { pte_t entry = READ_ONCE(*ptep); struct page *page; - int expected, rc = 0; + int expected, cc = 0; if (!pte_present(entry)) return -ENXIO; @@ -196,12 +196,25 @@ 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); + /* + * If the UVC does not succeed or fail immediately, we don't want to + * loop for long, or we might get stall notifications. + * On the other hand, this is a complex scenario and we are holding a lot of + * locks, so we can't easily sleep and reschedule. We try only once, + * and if the UVC returned busy or partial completion, we return + * -EAGAIN and we let the callers deal with it. + */ + cc = __uv_call(0, (u64)uvcb); page_ref_unfreeze(page, expected); - /* Return -ENXIO if the page was not mapped, -EINVAL otherwise */ - if (rc) - rc = uvcb->rc == 0x10a ? -ENXIO : -EINVAL; - return rc; + /* + * Return -ENXIO if the page was not mapped, -EINVAL for other errors. + * If busy or partially completed, return -EAGAIN. + */ + if (cc == UVC_CC_OK) + return 0; + else if (cc == UVC_CC_BUSY || cc == UVC_CC_PARTIAL) + return -EAGAIN; + return uvcb->rc == 0x10a ? -ENXIO : -EINVAL; } /* @@ -254,6 +267,10 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb) mmap_read_unlock(gmap->mm); if (rc == -EAGAIN) { + /* + * If we are here because the UVC returned busy or partial + * completion, this is just a useless check, but it is safe. + */ wait_on_page_writeback(page); } else if (rc == -EBUSY) { /* 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