From: Paul Durrant <paul@xen.org>
To: David Woodhouse <dwmw2@infradead.org>,
Paul Durrant <paul@xen.org>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.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>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v9 15/15] KVM: xen: allow vcpu_info content to be 'safely' copied
Date: Wed, 22 Nov 2023 12:18:22 +0000 [thread overview]
Message-ID: <20231122121822.1042-16-paul@xen.org> (raw)
In-Reply-To: <20231122121822.1042-1-paul@xen.org>
From: Paul Durrant <pdurrant@amazon.com>
If the guest sets an explicit vcpu_info GPA then, for any of the first 32
vCPUs, the content of the default vcpu_info in the shared_info page must be
copied into the new location. Because this copy may race with event
delivery (which updates the 'evtchn_pending_sel' field in vcpu_info) there
needs to be a way to defer that until the copy is complete.
Happily there is already a shadow of 'evtchn_pending_sel' in kvm_vcpu_xen
that is used in atomic context if the vcpu_info PFN cache has been
invalidated so that the update of vcpu_info can be deferred until the
cache can be refreshed (on vCPU thread's the way back into guest context).
Also use this shadow if the vcpu_info cache has been *deactivated*, so that
the VMM can safely copy the vcpu_info content and then re-activate the
cache with the new GPA. To do this, stop considering an inactive vcpu_info
cache as a hard error in kvm_xen_set_evtchn_fast().
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
---
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
v8:
- Update commit comment.
v6:
- New in this version.
---
arch/x86/kvm/xen.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index eff405eead1c..cfd5051e0800 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1742,9 +1742,6 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm)
WRITE_ONCE(xe->vcpu_idx, vcpu->vcpu_idx);
}
- if (!vcpu->arch.xen.vcpu_info_cache.active)
- return -EINVAL;
-
if (xe->port >= max_evtchn_port(kvm))
return -EINVAL;
--
2.39.2
prev parent reply other threads:[~2023-11-22 12:30 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-22 12:18 [PATCH v9 00/15] KVM: xen: update shared_info and vcpu_info handling Paul Durrant
2023-11-22 12:18 ` [PATCH v9 01/15] KVM: pfncache: Add a map helper function Paul Durrant
2023-11-22 12:18 ` [PATCH v9 02/15] KVM: pfncache: remove unnecessary exports Paul Durrant
2023-11-22 12:18 ` [PATCH v9 03/15] KVM: xen: mark guest pages dirty with the pfncache lock held Paul Durrant
2023-11-22 12:18 ` [PATCH v9 04/15] KVM: pfncache: add a mark-dirty helper Paul Durrant
2023-11-22 12:24 ` David Woodhouse
2023-11-22 13:04 ` Paul Durrant
2023-11-22 12:18 ` [PATCH v9 05/15] KVM: pfncache: remove KVM_GUEST_USES_PFN usage Paul Durrant
2023-11-22 12:18 ` [PATCH v9 06/15] KVM: pfncache: stop open-coding offset_in_page() Paul Durrant
2023-11-22 12:18 ` [PATCH v9 07/15] KVM: pfncache: include page offset in uhva and use it consistently Paul Durrant
2023-11-22 12:18 ` [PATCH v9 08/15] KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA Paul Durrant
2023-11-22 12:25 ` David Woodhouse
2023-11-22 12:18 ` [PATCH v9 09/15] KVM: xen: allow shared_info to be mapped by fixed HVA Paul Durrant
2023-11-22 12:18 ` [PATCH v9 10/15] KVM: xen: allow vcpu_info " Paul Durrant
2023-11-22 12:18 ` [PATCH v9 11/15] KVM: selftests / xen: map shared_info using HVA rather than GFN Paul Durrant
2023-11-22 12:18 ` [PATCH v9 12/15] KVM: selftests / xen: re-map vcpu_info using HVA rather than GPA Paul Durrant
2023-11-22 12:18 ` [PATCH v9 13/15] KVM: xen: advertize the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA capability Paul Durrant
2023-11-22 12:18 ` [PATCH v9 14/15] KVM: xen: split up kvm_xen_set_evtchn_fast() Paul Durrant
2023-11-22 12:18 ` Paul Durrant [this message]
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