Re: [PATCH v4 2/4] KVM: SVM: Use unsigned integers when dealing with ASIDs

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On 1/31/24 17:56, Sean Christopherson wrote:
Convert all local ASID variables and parameters throughout the SEV code
from signed integers to unsigned integers.  As ASIDs are fundamentally
unsigned values, and the global min/max variables are appropriately
unsigned integers, too.

Functionally, this is a glorified nop as KVM guarantees min_sev_asid is
non-zero, and no CPU supports -1u as the _only_ asid, i.e. the signed vs.
unsigned goof won't cause problems in practice.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

Just one minor comment below, but either way...

Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>

---
  arch/x86/kvm/svm/sev.c | 18 ++++++++++--------
  arch/x86/kvm/trace.h   | 10 +++++-----
  2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 7c000088bca6..04c4c14473fd 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 +144,9 @@ 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;
+	unsigned int asid, min_asid, max_asid;
  	bool retry = true;
+	int ret;
WARN_ON(sev->misc_cg);
  	sev->misc_cg = get_current_misc_cg();
@@ -188,7 +190,7 @@ static int sev_asid_new(struct kvm_sev_info *sev)
  	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;
@@ -284,8 +286,8 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp) 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 */
@@ -2312,7 +2314,7 @@ 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 = to_kvm_svm(vcpu->kvm)->sev_info.asid;

Since you're touching this, you could switch this to:

	unsigned int asid = sev_get_asid(vcpu->kvm);

/*
  	 * Note!  The address must be a kernel address, as regular page walk
@@ -2630,7 +2632,7 @@ 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 83843379813e..b82e6ed4f024 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -732,13 +732,13 @@ 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(
@@ -747,7 +747,7 @@ 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)
  );




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