Merge tag 'kvm-x86-fixes-6.17-rc7' of https://github.com/kvm-x86/linux into HEAD

KVM x86 fixes and a selftest fix for 6.17-rcN

 - Use array_index_nospec() to sanitize the target vCPU ID when handling PV
   IPIs and yields as the ID is guest-controlled.

 - Drop a superfluous cpumask_empty() check when reclaiming SEV memory, as
   the common case, by far, is that at least one CPU will have entered the
   VM, and wbnoinvd_on_cpus_mask() will naturally handle the rare case where
   the set of have_run_cpus is empty.

 - Rename the is_signed_type() macro in kselftest_harness.h to is_signed_var()
   to fix a collision with linux/overflow.h.  The collision generates compiler
   warnings due to the two macros having different implementations.

3 files changed, 10 insertions, 9 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 8172c2042dd6..5fc437341e03 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -810,6 +810,8 @@ static int __pv_send_ipi(unsigned long *ipi_bitmap, struct kvm_apic_map *map,
 	if (min > map->max_apic_id)
 		return 0;
 
+	min = array_index_nospec(min, map->max_apic_id + 1);
+
 	for_each_set_bit(i, ipi_bitmap,
 		min((u32)BITS_PER_LONG, (map->max_apic_id - min + 1))) {
 		if (map->phys_map[min + i]) {
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 2fbdebf79fbb..0635bd71c10e 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -719,13 +719,6 @@ static void sev_clflush_pages(struct page *pages[], unsigned long npages)
 static void sev_writeback_caches(struct kvm *kvm)
 {
 	/*
-	 * Note, the caller is responsible for ensuring correctness if the mask
-	 * can be modified, e.g. if a CPU could be doing VMRUN.
-	 */
-	if (cpumask_empty(to_kvm_sev_info(kvm)->have_run_cpus))
-		return;
-
-	/*
 	 * Ensure that all dirty guest tagged cache entries are written back
 	 * before releasing the pages back to the system for use.  CLFLUSH will
 	 * not do this without SME_COHERENT, and flushing many cache lines
@@ -739,6 +732,9 @@ static void sev_writeback_caches(struct kvm *kvm)
 	 * serializing multiple calls and having responding CPUs (to the IPI)
 	 * mark themselves as still running if they are running (or about to
 	 * run) a vCPU for the VM.
+	 *
+	 * Note, the caller is responsible for ensuring correctness if the mask
+	 * can be modified, e.g. if a CPU could be doing VMRUN.
 	 */
 	wbnoinvd_on_cpus_mask(to_kvm_sev_info(kvm)->have_run_cpus);
 }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a1c49bc681c4..604490b1cb19 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9908,8 +9908,11 @@ static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id)
 	rcu_read_lock();
 	map = rcu_dereference(vcpu->kvm->arch.apic_map);
 
-	if (likely(map) && dest_id <= map->max_apic_id && map->phys_map[dest_id])
-		target = map->phys_map[dest_id]->vcpu;
+	if (likely(map) && dest_id <= map->max_apic_id) {
+		dest_id = array_index_nospec(dest_id, map->max_apic_id + 1);
+		if (map->phys_map[dest_id])
+			target = map->phys_map[dest_id]->vcpu;
+	}
 
 	rcu_read_unlock();