Merge tag 'kvm-x86-svm-6.9' of https://github.com/kvm-x86/linux into HEAD

KVM SVM changes for 6.9:

 - Add support for systems that are configured with SEV and SEV-ES+ enabled,
   but have all ASIDs assigned to SEV-ES+ guests, which effectively makes SEV
   unusuable.  Cleanup ASID handling to make supporting this scenario less
   brittle/ugly.

 - Return -EINVAL instead of -EBUSY if userspace attempts to invoke
   KVM_SEV{,ES}_INIT on an SEV+ guest.  The operation is simply invalid, and
   not related to resource contention in any way.

2 files changed, 39 insertions, 29 deletions

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index ae0ac12382b92..e5a4d9b0e79fd 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -84,9 +84,10 @@ struct enc_region {
 };
 
 /* Called with the sev_bitmap_lock held, or on shutdown  */
-static int sev_flush_asids(int min_asid, int max_asid)
+static int sev_flush_asids(unsigned int min_asid, unsigned int max_asid)
 {
-	int ret, asid, error = 0;
+	int ret, error = 0;
+	unsigned int asid;
 
 	/* Check if there are any ASIDs to reclaim before performing a flush */
 	asid = find_next_bit(sev_reclaim_asid_bitmap, nr_asids, min_asid);
@@ -116,7 +117,7 @@ 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)
+static bool __sev_recycle_asids(unsigned int min_asid, unsigned int max_asid)
 {
 	if (sev_flush_asids(min_asid, max_asid))
 		return false;
@@ -143,8 +144,20 @@ static void sev_misc_cg_uncharge(struct kvm_sev_info *sev)
 
 static int sev_asid_new(struct kvm_sev_info *sev)
 {
-	int asid, min_asid, max_asid, ret;
+	/*
+	 * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid.
+	 * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1.
+	 * Note: min ASID can end up larger than the max if basic SEV support is
+	 * effectively disabled by disallowing use of ASIDs for SEV guests.
+	 */
+	unsigned int min_asid = sev->es_active ? 1 : min_sev_asid;
+	unsigned int max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid;
+	unsigned int asid;
 	bool retry = true;
+	int ret;
+
+	if (min_asid > max_asid)
+		return -ENOTTY;
 
 	WARN_ON(sev->misc_cg);
 	sev->misc_cg = get_current_misc_cg();
@@ -157,12 +170,6 @@ static int sev_asid_new(struct kvm_sev_info *sev)
 
 	mutex_lock(&sev_bitmap_lock);
 
-	/*
-	 * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid.
-	 * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1.
-	 */
-	min_asid = sev->es_active ? 1 : min_sev_asid;
-	max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid;
 again:
 	asid = find_next_zero_bit(sev_asid_bitmap, max_asid + 1, min_asid);
 	if (asid > max_asid) {
@@ -179,7 +186,8 @@ again:
 
 	mutex_unlock(&sev_bitmap_lock);
 
-	return asid;
+	sev->asid = asid;
+	return 0;
 e_uncharge:
 	sev_misc_cg_uncharge(sev);
 	put_misc_cg(sev->misc_cg);
@@ -187,7 +195,7 @@ e_uncharge:
 	return ret;
 }
 
-static int sev_get_asid(struct kvm *kvm)
+static unsigned int sev_get_asid(struct kvm *kvm)
 {
 	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
 
@@ -247,21 +255,19 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
 {
 	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
 	struct sev_platform_init_args init_args = {0};
-	int asid, ret;
+	int ret;
 
 	if (kvm->created_vcpus)
 		return -EINVAL;
 
-	ret = -EBUSY;
 	if (unlikely(sev->active))
-		return ret;
+		return -EINVAL;
 
 	sev->active = true;
 	sev->es_active = argp->id == KVM_SEV_ES_INIT;
-	asid = sev_asid_new(sev);
-	if (asid < 0)
+	ret = sev_asid_new(sev);
+	if (ret)
 		goto e_no_asid;
-	sev->asid = asid;
 
 	init_args.probe = false;
 	ret = sev_platform_init(&init_args);
@@ -287,8 +293,8 @@ e_no_asid:
 
 static int sev_bind_asid(struct kvm *kvm, unsigned int handle, int *error)
 {
+	unsigned int asid = sev_get_asid(kvm);
 	struct sev_data_activate activate;
-	int asid = sev_get_asid(kvm);
 	int ret;
 
 	/* activate ASID on the given handle */
@@ -2240,8 +2246,10 @@ void __init sev_hardware_setup(void)
 		goto out;
 	}
 
-	sev_asid_count = max_sev_asid - min_sev_asid + 1;
-	WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count));
+	if (min_sev_asid <= max_sev_asid) {
+		sev_asid_count = max_sev_asid - min_sev_asid + 1;
+		WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count));
+	}
 	sev_supported = true;
 
 	/* SEV-ES support requested? */
@@ -2272,7 +2280,9 @@ void __init sev_hardware_setup(void)
 out:
 	if (boot_cpu_has(X86_FEATURE_SEV))
 		pr_info("SEV %s (ASIDs %u - %u)\n",
-			sev_supported ? "enabled" : "disabled",
+			sev_supported ? min_sev_asid <= max_sev_asid ? "enabled" :
+								       "unusable" :
+								       "disabled",
 			min_sev_asid, max_sev_asid);
 	if (boot_cpu_has(X86_FEATURE_SEV_ES))
 		pr_info("SEV-ES %s (ASIDs %u - %u)\n",
@@ -2320,7 +2330,7 @@ int sev_cpu_init(struct svm_cpu_data *sd)
  */
 static void sev_flush_encrypted_page(struct kvm_vcpu *vcpu, void *va)
 {
-	int asid = to_kvm_svm(vcpu->kvm)->sev_info.asid;
+	unsigned int asid = sev_get_asid(vcpu->kvm);
 
 	/*
 	 * Note!  The address must be a kernel address, as regular page walk
@@ -2638,7 +2648,7 @@ void sev_es_unmap_ghcb(struct vcpu_svm *svm)
 void pre_sev_run(struct vcpu_svm *svm, int cpu)
 {
 	struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, cpu);
-	int asid = sev_get_asid(svm->vcpu.kvm);
+	unsigned int asid = sev_get_asid(svm->vcpu.kvm);
 
 	/* Assign the asid allocated with this SEV guest */
 	svm->asid = asid;
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 88659de4d2a71..c6b4b1728006d 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -735,13 +735,13 @@ TRACE_EVENT(kvm_nested_intr_vmexit,
  * Tracepoint for nested #vmexit because of interrupt pending
  */
 TRACE_EVENT(kvm_invlpga,
-	    TP_PROTO(__u64 rip, int asid, u64 address),
+	    TP_PROTO(__u64 rip, unsigned int asid, u64 address),
 	    TP_ARGS(rip, asid, address),
 
 	TP_STRUCT__entry(
-		__field(	__u64,	rip	)
-		__field(	int,	asid	)
-		__field(	__u64,	address	)
+		__field(	__u64,		rip	)
+		__field(	unsigned int,	asid	)
+		__field(	__u64,		address	)
 	),
 
 	TP_fast_assign(
@@ -750,7 +750,7 @@ TRACE_EVENT(kvm_invlpga,
 		__entry->address	=	address;
 	),
 
-	TP_printk("rip: 0x%016llx asid: %d address: 0x%016llx",
+	TP_printk("rip: 0x%016llx asid: %u address: 0x%016llx",
 		  __entry->rip, __entry->asid, __entry->address)
 );