[PATCH v1 16/44] KVM: arm64: Do not map the host fpsimd state to hyp in pKVM

[Fuad Tabba <tabba@google.com>]

pKVM maintains its own state for tracking the host fpsimd state.
Therefore, no need to map and share the host's view with it.

Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/arm64/include/asm/kvm_host.h |  2 --
 arch/arm64/kvm/fpsimd.c           | 31 ++++---------------------------
 arch/arm64/kvm/reset.c            |  1 -
 3 files changed, 4 insertions(+), 30 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 3d12fc2aeb9e..cdbbfa3246c1 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -642,7 +642,6 @@ struct kvm_vcpu_arch {
 	struct kvm_guest_debug_arch external_debug_state;
 
 	struct user_fpsimd_state *host_fpsimd_state;	/* hyp VA */
-	struct task_struct *parent_task;
 
 	struct {
 		/* {Break,watch}point registers */
@@ -1214,7 +1213,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
-void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu);
 
 static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
 {
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index f297e89e4810..e3d9ec4ab9d0 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -14,19 +14,6 @@
 #include <asm/kvm_mmu.h>
 #include <asm/sysreg.h>
 
-void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu)
-{
-	struct task_struct *p = vcpu->arch.parent_task;
-	struct user_fpsimd_state *fpsimd;
-
-	if (!is_protected_kvm_enabled() || !p)
-		return;
-
-	fpsimd = &p->thread.uw.fpsimd_state;
-	kvm_unshare_hyp(fpsimd, fpsimd + 1);
-	put_task_struct(p);
-}
-
 /*
  * Called on entry to KVM_RUN unless this vcpu previously ran at least
  * once and the most recent prior KVM_RUN for this vcpu was called from
@@ -38,11 +25,12 @@ void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu)
  */
 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
 {
-	int ret;
-
 	struct user_fpsimd_state *fpsimd = &current->thread.uw.fpsimd_state;
+	int ret;
 
-	kvm_vcpu_unshare_task_fp(vcpu);
+	/* pKVM has its own tracking of the host fpsimd state. */
+	if (is_protected_kvm_enabled())
+		return 0;
 
 	/* Make sure the host task fpsimd state is visible to hyp: */
 	ret = kvm_share_hyp(fpsimd, fpsimd + 1);
@@ -51,17 +39,6 @@ int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
 
 	vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
 
-	/*
-	 * We need to keep current's task_struct pinned until its data has been
-	 * unshared with the hypervisor to make sure it is not re-used by the
-	 * kernel and donated to someone else while already shared -- see
-	 * kvm_vcpu_unshare_task_fp() for the matching put_task_struct().
-	 */
-	if (is_protected_kvm_enabled()) {
-		get_task_struct(current);
-		vcpu->arch.parent_task = current;
-	}
-
 	return 0;
 }
 
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 29ae68f60bef..3d8064bf67c8 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -139,7 +139,6 @@ void kvm_arm_vcpu_destroy(struct kvm_vcpu *vcpu)
 {
 	void *sve_state = vcpu->arch.sve_state;
 
-	kvm_vcpu_unshare_task_fp(vcpu);
 	kvm_unshare_hyp(vcpu, vcpu + 1);
 	if (sve_state)
 		kvm_unshare_hyp(sve_state, sve_state + vcpu_sve_state_size(vcpu));
-- 
2.44.0.478.gd926399ef9-goog