From: Eric Farman <farman@linux.ibm.com>
To: Christian Borntraeger <borntraeger@linux.ibm.com>,
Janosch Frank <frankja@linux.ibm.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
David Hildenbrand <david@redhat.com>
Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Sven Schnelle <svens@linux.ibm.com>,
Eric Farman <farman@linux.ibm.com>
Subject: [PATCH] KVM: s390: vsie: retry SIE instruction on host intercepts
Date: Fri, 1 Mar 2024 21:43:42 +0100 [thread overview]
Message-ID: <20240301204342.3217540-1-farman@linux.ibm.com> (raw)
It's possible that SIE exits for work that the host needs to perform
rather than something that is intended for the guest.
A Linux guest will ignore this intercept code since there is nothing
for it to do, but a more robust solution would rewind the PSW back to
the SIE instruction. This will transparently resume the guest once
the host completes its work, without the guest needing to process
what is effectively a NOP and re-issue SIE itself.
Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
arch/s390/kvm/vsie.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 8f0f944f81c2..63aae70a6790 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -1306,10 +1306,24 @@ static int vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
if (rc == -EAGAIN)
rc = 0;
- if (rc || scb_s->icptcode || signal_pending(current) ||
+
+ /*
+ * Exit the loop if the guest needs to process the intercept
+ */
+ if (rc || scb_s->icptcode)
+ break;
+
+ /*
+ * Exit the loop if the host needs to process an intercept,
+ * but rewind the PSW to re-enter SIE once that's completed
+ * instead of passing a "no action" intercept to the guest.
+ */
+ if (signal_pending(current) ||
kvm_s390_vcpu_has_irq(vcpu, 0) ||
- kvm_s390_vcpu_sie_inhibited(vcpu))
+ kvm_s390_vcpu_sie_inhibited(vcpu)) {
+ kvm_s390_rewind_psw(vcpu, 4);
break;
+ }
cond_resched();
}
@@ -1428,8 +1442,10 @@ int kvm_s390_handle_vsie(struct kvm_vcpu *vcpu)
return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
if (signal_pending(current) || kvm_s390_vcpu_has_irq(vcpu, 0) ||
- kvm_s390_vcpu_sie_inhibited(vcpu))
+ kvm_s390_vcpu_sie_inhibited(vcpu)) {
+ kvm_s390_rewind_psw(vcpu, 4);
return 0;
+ }
vsie_page = get_vsie_page(vcpu->kvm, scb_addr);
if (IS_ERR(vsie_page))
--
2.40.1
next reply other threads:[~2024-03-01 20:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-01 20:43 Eric Farman [this message]
2024-03-04 8:35 ` [PATCH] KVM: s390: vsie: retry SIE instruction on host intercepts David Hildenbrand
2024-03-04 8:44 ` Christian Borntraeger
2024-03-04 15:37 ` Eric Farman
2024-04-29 10:18 ` Christian Borntraeger
2024-04-30 19:31 ` Eric Farman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240301204342.3217540-1-farman@linux.ibm.com \
--to=farman@linux.ibm.com \
--cc=agordeev@linux.ibm.com \
--cc=borntraeger@linux.ibm.com \
--cc=david@redhat.com \
--cc=frankja@linux.ibm.com \
--cc=gor@linux.ibm.com \
--cc=hca@linux.ibm.com \
--cc=imbrenda@linux.ibm.com \
--cc=kvm@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=svens@linux.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).