From: Claudio Imbrenda <imbrenda@linux.ibm.com>
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 [thread overview]
Message-ID: <20210804154046.88552-3-imbrenda@linux.ibm.com> (raw)
In-Reply-To: <20210804154046.88552-1-imbrenda@linux.ibm.com>
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>
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
next prev parent reply other threads:[~2021-08-04 15:41 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-04 15:40 [PATCH v3 00/14] KVM: s390: pv: implement lazy destroy Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 01/14] KVM: s390: pv: add macros for UVC CC values Claudio Imbrenda
2021-08-06 7:26 ` David Hildenbrand
2021-08-06 9:34 ` Claudio Imbrenda
2021-08-06 15:15 ` Janosch Frank
2021-08-04 15:40 ` Claudio Imbrenda [this message]
2021-08-06 7:30 ` [PATCH v3 02/14] KVM: s390: pv: avoid stall notifications for some UVCs David Hildenbrand
2021-08-06 9:33 ` Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 03/14] KVM: s390: pv: leak the ASCE page when destroy fails Claudio Imbrenda
2021-08-06 7:31 ` David Hildenbrand
2021-08-06 9:32 ` Claudio Imbrenda
2021-08-06 11:39 ` David Hildenbrand
2021-08-04 15:40 ` [PATCH v3 04/14] KVM: s390: pv: properly handle page flags for protected guests Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 05/14] KVM: s390: pv: handle secure storage violations " Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 06/14] KVM: s390: pv: handle secure storage exceptions for normal guests Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 07/14] KVM: s390: pv: refactor s390_reset_acc Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 08/14] KVM: s390: pv: usage counter instead of flag Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 09/14] KVM: s390: pv: add export before import Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 10/14] KVM: s390: pv: lazy destroy for reboot Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 11/14] KVM: s390: pv: extend lazy destroy to handle shutdown Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 12/14] KVM: s390: pv: module parameter to fence lazy destroy Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 13/14] KVM: s390: pv: add OOM notifier for " Claudio Imbrenda
2021-08-04 15:40 ` [PATCH v3 14/14] KVM: s390: pv: avoid export before import if possible Claudio Imbrenda
2021-08-06 7:10 ` [PATCH v3 00/14] KVM: s390: pv: implement lazy destroy David Hildenbrand
2021-08-06 9:30 ` Claudio Imbrenda
2021-08-06 11:30 ` David Hildenbrand
2021-08-06 13:44 ` Claudio Imbrenda
2021-08-09 8:50 ` David Hildenbrand
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