From: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>
To: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Sean Christopherson" <sean.j.christopherson@intel.com>,
"Vitaly Kuznetsov" <vkuznets@redhat.com>,
"Wanpeng Li" <wanpengli@tencent.com>,
"Jim Mattson" <jmattson@google.com>,
"Joerg Roedel" <joro@8bytes.org>,
"Singh, Brijesh" <brijesh.singh@amd.com>,
"David Rientjes" <rientjes@google.com>
Subject: [PATCH 2/5] KVM: SVM: Guard against DEACTIVATE when performing WBINVD/DF_FLUSH
Date: Thu, 3 Oct 2019 21:17:45 +0000 [thread overview]
Message-ID: <a45e629505eeb15a96ede97c9c6484bd62195228.1570137447.git.thomas.lendacky@amd.com> (raw)
In-Reply-To: <cover.1570137447.git.thomas.lendacky@amd.com>
From: Tom Lendacky <thomas.lendacky@amd.com>
The SEV firmware DEACTIVATE command disassociates an SEV guest from an
ASID, clears the WBINVD indicator on all threads and indicates that the
SEV firmware DF_FLUSH command must be issued before the ASID can be
re-used. The SEV firmware DF_FLUSH command will return an error if a
WBINVD has not been performed on every thread before it has been invoked.
A window exists between the WBINVD and the invocation of the DF_FLUSH
command where an SEV firmware DEACTIVATE command could be invoked on
another thread, clearing the WBINVD indicator. This will cause the
subsequent SEV firmware DF_FLUSH command to fail which, in turn, results
in the SEV firmware ACTIVATE command failing for the reclaimed ASID.
This results in the SEV guest failing to start.
Use a mutex to close the WBINVD/DF_FLUSH window by obtaining the mutex
before the DEACTIVATE and releasing it after the DF_FLUSH. This ensures
that any DEACTIVATE cannot run before a DF_FLUSH has completed.
Fixes: 59414c989220 ("KVM: SVM: Add support for KVM_SEV_LAUNCH_START command")
Tested-by: David Rientjes <rientjes@google.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
arch/x86/kvm/svm.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index d371007ab109..1d217680cf83 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -418,6 +418,7 @@ enum {
#define VMCB_AVIC_APIC_BAR_MASK 0xFFFFFFFFFF000ULL
+static DEFINE_MUTEX(sev_deactivate_lock);
static DEFINE_MUTEX(sev_bitmap_lock);
static unsigned int max_sev_asid;
static unsigned int min_sev_asid;
@@ -1756,10 +1757,20 @@ static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
/* deactivate handle */
data->handle = handle;
+
+ /*
+ * Guard against a parallel DEACTIVATE command before the DF_FLUSH
+ * command has completed.
+ */
+ mutex_lock(&sev_deactivate_lock);
+
sev_guest_deactivate(data, NULL);
wbinvd_on_all_cpus();
sev_guest_df_flush(NULL);
+
+ mutex_unlock(&sev_deactivate_lock);
+
kfree(data);
decommission = kzalloc(sizeof(*decommission), GFP_KERNEL);
@@ -6318,9 +6329,18 @@ static int sev_bind_asid(struct kvm *kvm, unsigned int handle, int *error)
int asid = sev_get_asid(kvm);
int ret;
+ /*
+ * Guard against a DEACTIVATE command before the DF_FLUSH command
+ * has completed.
+ */
+ mutex_lock(&sev_deactivate_lock);
+
wbinvd_on_all_cpus();
ret = sev_guest_df_flush(error);
+
+ mutex_unlock(&sev_deactivate_lock);
+
if (ret)
return ret;
--
2.17.1
next prev parent reply other threads:[~2019-10-03 21:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-03 21:17 [PATCH 0/5] SEV fixes and performance enhancements Lendacky, Thomas
2019-10-03 21:17 ` [PATCH 1/5] KVM: SVM: Serialize access to the SEV ASID bitmap Lendacky, Thomas
2019-10-04 17:25 ` Jim Mattson
2019-10-03 21:17 ` Lendacky, Thomas [this message]
2019-10-03 21:17 ` [PATCH 3/5] KVM: SVM: Remove unneeded WBINVD and DF_FLUSH when starting SEV guests Lendacky, Thomas
2019-10-03 21:17 ` [PATCH 4/5] KVM: SVM: Convert DEACTIVATE mutex to read/write semaphore Lendacky, Thomas
2019-10-03 21:17 ` [PATCH 5/5] KVM: SVM: Reduce WBINVD/DF_FLUSH invocations Lendacky, Thomas
2019-10-09 10:08 ` [PATCH 0/5] SEV fixes and performance enhancements Paolo Bonzini
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