[PATCH] KVM: arm64: Remove kvm_arch_vcpu_run_map_fp()

[Mark Rutland]

Historically KVM hyp code saved the host's FPSIMD state into the hosts's
fpsimd_state memory, and so it was necessary to map this into the hyp
Stage-1 mappings before running a vCPU.

This is no longer necessary as of commits:

* fbc7e61195e2 ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state")
* 8eca7f6d5100 ("KVM: arm64: Remove host FPSIMD saving for non-protected KVM")

Since those commits, we eagerly save the host's FPSIMD state before
calling into hyp to run a vCPU, and hyp code never reads nor writes the
host's fpsimd_state memory. There's no longer any need to map the host's
fpsimd_state memory into the hyp Stage-1, and kvm_arch_vcpu_run_map_fp()
is unnecessary but benign.

Remove kvm_arch_vcpu_run_map_fp(). Currently there is no code to perform
a corresponding unmap, and we never mapped the host's SVE or SME state
into the hyp Stage-1, so no other code needs to be removed.

Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Fuad Tabba <tabba at google.com>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Mark Brown <broonie at kernel.org>
Cc: Oliver Upton <oliver.upton at linux.dev>
Cc: Will Deacon <will at kernel.org>
Cc: kvmarm at lists.linux.dev
---
 arch/arm64/include/asm/kvm_host.h |  1 -
 arch/arm64/kvm/arm.c              |  4 ----
 arch/arm64/kvm/fpsimd.c           | 26 --------------------------
 3 files changed, 31 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 5ccca509dff1a..f7ad74404202b 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1482,7 +1482,6 @@ int kvm_vm_ioctl_get_reg_writable_masks(struct kvm *kvm,
 					struct reg_mask_range *range);
 
 /* Guest/host FPSIMD coordination helpers */
-int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu);
 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);
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index de2b4e9c9f9fb..1502faa460863 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -825,10 +825,6 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
 	if (!kvm_arm_vcpu_is_finalized(vcpu))
 		return -EPERM;
 
-	ret = kvm_arch_vcpu_run_map_fp(vcpu);
-	if (ret)
-		return ret;
-
 	if (likely(vcpu_has_run_once(vcpu)))
 		return 0;
 
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 8f6c8f57c6b9c..15e17aca1dec0 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -14,32 +14,6 @@
 #include <asm/kvm_mmu.h>
 #include <asm/sysreg.h>
 
-/*
- * 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
- * the same task as current (highly likely).
- *
- * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu),
- * such that on entering hyp the relevant parts of current are already
- * mapped.
- */
-int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
-{
-	struct user_fpsimd_state *fpsimd = &current->thread.uw.fpsimd_state;
-	int ret;
-
-	/* 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);
-	if (ret)
-		return ret;
-
-	return 0;
-}
-
 /*
  * Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
  * The actual loading is done by the FPSIMD access trap taken to hyp.
-- 
2.30.2