From: Sean Christopherson <seanjc@google.com>
Date: Thu, 22 Apr 2021 02:11:25 +0000 (-0700)
Subject: KVM: SVM: Skip SEV cache flush if no ASIDs have been used
X-Git-Tag: v5.13-rc1~76^2~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=469bb32b68d5a414fea293c17b532329c6dc9612;p=thirdparty%2Flinux.git

KVM: SVM: Skip SEV cache flush if no ASIDs have been used

Skip SEV's expensive WBINVD and DF_FLUSH if there are no SEV ASIDs
waiting to be reclaimed, e.g. if SEV was never used.  This "fixes" an
issue where the DF_FLUSH fails during hardware teardown if the original
SEV_INIT failed.  Ideally, SEV wouldn't be marked as enabled in KVM if
SEV_INIT fails, but that's a problem for another day.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210422021125.3417167-16-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index fd3ffc103ed8a..a9d8d6aafdb8a 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -74,9 +74,15 @@ struct enc_region {
 	unsigned long size;
 };
 
-static int sev_flush_asids(void)
+/* Called with the sev_bitmap_lock held, or on shutdown  */
+static int sev_flush_asids(int min_asid, int max_asid)
 {
-	int ret, error = 0;
+	int ret, pos, error = 0;
+
+	/* Check if there are any ASIDs to reclaim before performing a flush */
+	pos = find_next_bit(sev_reclaim_asid_bitmap, max_asid, min_asid);
+	if (pos >= max_asid)
+		return -EBUSY;
 
 	/*
 	 * DEACTIVATE will clear the WBINVD indicator causing DF_FLUSH to fail,
@@ -103,14 +109,7 @@ static inline bool is_mirroring_enc_context(struct kvm *kvm)
 /* Must be called with the sev_bitmap_lock held */
 static bool __sev_recycle_asids(int min_asid, int max_asid)
 {
-	int pos;
-
-	/* Check if there are any ASIDs to reclaim before performing a flush */
-	pos = find_next_bit(sev_reclaim_asid_bitmap, max_sev_asid, min_asid);
-	if (pos >= max_asid)
-		return false;
-
-	if (sev_flush_asids())
+	if (sev_flush_asids(min_asid, max_asid))
 		return false;
 
 	/* The flush process will flush all reclaimable SEV and SEV-ES ASIDs */
@@ -1897,12 +1896,14 @@ void sev_hardware_teardown(void)
 	if (!sev_enabled)
 		return;
 
+	/* No need to take sev_bitmap_lock, all VMs have been destroyed. */
+	sev_flush_asids(0, max_sev_asid);
+
 	bitmap_free(sev_asid_bitmap);
 	bitmap_free(sev_reclaim_asid_bitmap);
+
 	misc_cg_set_capacity(MISC_CG_RES_SEV, 0);
 	misc_cg_set_capacity(MISC_CG_RES_SEV_ES, 0);
-
-	sev_flush_asids();
 }
 
 int sev_cpu_init(struct svm_cpu_data *sd)