From: Paul Durrant <paul@xen.org>
To: Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Sean Christopherson <seanjc@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
David Woodhouse <dwmw2@infradead.org>,
Paul Durrant <paul@xen.org>, Shuah Khan <shuah@kernel.org>,
kvm@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: [PATCH v12 18/20] KVM: pfncache: check the need for invalidation under read lock first
Date: Mon, 15 Jan 2024 12:57:05 +0000 [thread overview]
Message-ID: <20240115125707.1183-19-paul@xen.org> (raw)
In-Reply-To: <20240115125707.1183-1-paul@xen.org>
From: Paul Durrant <pdurrant@amazon.com>
Taking a write lock on a pfncache will be disruptive if the cache is
heavily used (which only requires a read lock). Hence, in the MMU notifier
callback, take read locks on caches to check for a match; only taking a
write lock to actually perform an invalidation (after a another check).
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
---
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
v10:
- New in this version.
---
virt/kvm/pfncache.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index ae822bff812f..70394d7c9a38 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -29,14 +29,30 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, unsigned long start,
spin_lock(&kvm->gpc_lock);
list_for_each_entry(gpc, &kvm->gpc_list, list) {
- write_lock_irq(&gpc->lock);
+ read_lock_irq(&gpc->lock);
/* Only a single page so no need to care about length */
if (gpc->valid && !is_error_noslot_pfn(gpc->pfn) &&
gpc->uhva >= start && gpc->uhva < end) {
- gpc->valid = false;
+ read_unlock_irq(&gpc->lock);
+
+ /*
+ * There is a small window here where the cache could
+ * be modified, and invalidation would no longer be
+ * necessary. Hence check again whether invalidation
+ * is still necessary once the write lock has been
+ * acquired.
+ */
+
+ write_lock_irq(&gpc->lock);
+ if (gpc->valid && !is_error_noslot_pfn(gpc->pfn) &&
+ gpc->uhva >= start && gpc->uhva < end)
+ gpc->valid = false;
+ write_unlock_irq(&gpc->lock);
+ continue;
}
- write_unlock_irq(&gpc->lock);
+
+ read_unlock_irq(&gpc->lock);
}
spin_unlock(&kvm->gpc_lock);
}
--
2.39.2
next prev parent reply other threads:[~2024-01-15 13:09 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-15 12:56 [PATCH v12 00/20] KVM: xen: update shared_info and vcpu_info handling Paul Durrant
2024-01-15 12:56 ` [PATCH v12 01/20] KVM: pfncache: Add a map helper function Paul Durrant
2024-01-15 12:56 ` [PATCH v12 02/20] KVM: pfncache: remove unnecessary exports Paul Durrant
2024-01-15 12:56 ` [PATCH v12 03/20] KVM: xen: mark guest pages dirty with the pfncache lock held Paul Durrant
2024-02-07 3:17 ` Sean Christopherson
2024-02-07 3:26 ` David Woodhouse
2024-02-07 15:15 ` Sean Christopherson
2024-02-07 8:48 ` Paul Durrant
2024-01-15 12:56 ` [PATCH v12 04/20] KVM: pfncache: add a mark-dirty helper Paul Durrant
2024-02-07 3:20 ` Sean Christopherson
2024-02-07 8:47 ` Paul Durrant
2024-02-09 15:58 ` Sean Christopherson
2024-02-09 16:05 ` Paul Durrant
2024-01-15 12:56 ` [PATCH v12 05/20] KVM: pfncache: remove KVM_GUEST_USES_PFN usage Paul Durrant
2024-01-15 12:56 ` [PATCH v12 06/20] KVM: pfncache: stop open-coding offset_in_page() Paul Durrant
2024-01-15 12:56 ` [PATCH v12 07/20] KVM: pfncache: include page offset in uhva and use it consistently Paul Durrant
2024-01-15 12:56 ` [PATCH v12 08/20] KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA Paul Durrant
2024-02-07 4:03 ` Sean Christopherson
2024-02-07 4:13 ` David Woodhouse
2024-02-14 16:01 ` Sean Christopherson
2024-02-14 16:09 ` Paul Durrant
2024-02-14 15:21 ` Paul Durrant
2024-02-14 16:20 ` Sean Christopherson
2024-02-14 16:33 ` Paul Durrant
2024-01-15 12:56 ` [PATCH v12 09/20] KVM: xen: separate initialization of shared_info cache and content Paul Durrant
2024-01-15 12:56 ` [PATCH v12 10/20] KVM: xen: re-initialize shared_info if guest (32/64-bit) mode is set Paul Durrant
2024-01-15 12:56 ` [PATCH v12 11/20] KVM: xen: allow shared_info to be mapped by fixed HVA Paul Durrant
2024-02-07 4:10 ` Sean Christopherson
2024-02-07 8:53 ` Paul Durrant
2024-02-08 8:52 ` Paul Durrant
2024-02-08 16:48 ` Sean Christopherson
2024-02-08 16:51 ` Paul Durrant
2024-02-08 17:26 ` David Woodhouse
2024-02-09 16:01 ` Sean Christopherson
2024-01-15 12:56 ` [PATCH v12 12/20] KVM: xen: allow vcpu_info " Paul Durrant
2024-01-15 12:57 ` [PATCH v12 13/20] KVM: selftests / xen: map shared_info using HVA rather than GFN Paul Durrant
2024-02-07 4:14 ` Sean Christopherson
2024-02-07 8:54 ` Paul Durrant
2024-02-07 14:58 ` Sean Christopherson
2024-01-15 12:57 ` [PATCH v12 14/20] KVM: selftests / xen: re-map vcpu_info using HVA rather than GPA Paul Durrant
2024-01-15 12:57 ` [PATCH v12 15/20] KVM: xen: advertize the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA capability Paul Durrant
2024-01-15 12:57 ` [PATCH v12 16/20] KVM: xen: split up kvm_xen_set_evtchn_fast() Paul Durrant
2024-01-15 12:57 ` [PATCH v12 17/20] KVM: xen: don't block on pfncache locks in kvm_xen_set_evtchn_fast() Paul Durrant
2024-02-07 4:17 ` Sean Christopherson
2024-02-07 4:21 ` David Woodhouse
2024-01-15 12:57 ` Paul Durrant [this message]
2024-02-07 4:22 ` [PATCH v12 18/20] KVM: pfncache: check the need for invalidation under read lock first Sean Christopherson
2024-02-07 4:27 ` David Woodhouse
2024-02-07 4:47 ` Sean Christopherson
2024-02-07 4:59 ` David Woodhouse
2024-02-07 15:10 ` Sean Christopherson
2024-01-15 12:57 ` [PATCH v12 19/20] KVM: xen: allow vcpu_info content to be 'safely' copied Paul Durrant
2024-01-15 12:57 ` [PATCH v12 20/20] KVM: pfncache: rework __kvm_gpc_refresh() to fix locking issues Paul Durrant
2024-01-25 15:03 ` [PATCH v12 00/20] KVM: xen: update shared_info and vcpu_info handling Paul Durrant
2024-01-25 20:07 ` David Woodhouse
2024-01-26 1:19 ` Sean Christopherson
2024-02-02 17:37 ` Paul Durrant
2024-02-02 22:03 ` Sean Christopherson
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=20240115125707.1183-19-paul@xen.org \
--to=paul@xen.org \
--cc=bp@alien8.de \
--cc=corbet@lwn.net \
--cc=dave.hansen@linux.intel.com \
--cc=dwmw2@infradead.org \
--cc=hpa@zytor.com \
--cc=kvm@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=seanjc@google.com \
--cc=shuah@kernel.org \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/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 NNTP newsgroup(s).