linux-kernel - [PATCH 2/7] KVM: SVM: Use unsigned integers when dealing with ASIDs

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Message-ID: <20240318221002.2712738-3-pbonzini@redhat.com>
Date: Mon, 18 Mar 2024 18:09:57 -0400
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc: seanjc@...gle.com,
	Tom Lendacky <thomas.lendacky@....com>
Subject: [PATCH 2/7] KVM: SVM: Use unsigned integers when dealing with ASIDs

From: Sean Christopherson <seanjc@...gle.com>

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.

Opportunistically use sev_get_asid() in sev_flush_encrypted_page() instead
of open coding an equivalent.

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
Link: https://lore.kernel.org/r/20240131235609.4161407-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 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..eeef43c795d8 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 = 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 88659de4d2a7..c6b4b1728006 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)
 );
 
-- 
2.43.0