Commit 42ce4325 authored by Mark Rutland's avatar Mark Rutland Committed by Marc Zyngier
Browse files

KVM: arm64: Remove kvm_arch_vcpu_run_map_fp() 



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:

* fbc7e611 ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state")
* 8eca7f6d ("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: default avatarMark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Will Deacon <will@kernel.org>
Cc: kvmarm@lists.linux.dev
Reviewed-by: default avatarMark Brown <broonie@kernel.org>
Tested-by: default avatarFuad Tabba <tabba@google.com>
Reviewed-by: default avatarFuad Tabba <tabba@google.com>
Link: https://lore.kernel.org/r/20250619134817.4075340-1-mark.rutland@arm.com


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 105485a1

arch/arm64/include/asm/kvm_host.h

+0 −1
Original line number Diff line number Diff line
@@ -1480,7 +1480,6 @@ 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);

arch/arm64/kvm/arm.c

+0 −4
Original line number Diff line number Diff line
@@ -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;

arch/arm64/kvm/fpsimd.c

+0 −26
Original line number Diff line number Diff line
@@ -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.