Commit 64330073 authored by Marc Zyngier's avatar Marc Zyngier
Browse files

Merge branch kvm-arm64/fpsimd-doc into kvmarm-master/next 



* kvm-arm64/fpsimd-doc:
  : .
  : FPSIMD documentation update, courtesy of Mark Brown
  : .
  arm64/fpsimd: Clarify the purpose of using last in fpsimd_save()
  KVM: arm64: Add some more comments in kvm_hyp_handle_fpsimd()
  KVM: arm64: Add comments for context flush and sync callbacks

Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parents 2bb48074 432110cd

arch/arm64/kernel/fpsimd.c

+7 −1
Original line number Diff line number Diff line
@@ -348,7 +348,13 @@ static void task_fpsimd_load(void) 


/*

 * Ensure FPSIMD/SVE storage in memory for the loaded context is up to

 * date with respect to the CPU registers.

 * date with respect to the CPU registers. Note carefully that the

 * current context is the context last bound to the CPU stored in

 * last, if KVM is involved this may be the guest VM context rather

 * than the host thread for the VM pointed to by current. This means

 * that we must always reference the state storage via last rather

 * than via current, other than the TIF_ flags which KVM will

 * carefully maintain for us.

 */

static void fpsimd_save(void)

{

arch/arm64/kvm/fpsimd.c

+10 −4
Original line number Diff line number Diff line
@@ -84,6 +84,11 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) 
		vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;

}



/*

 * Called just before entering the guest once we are no longer

 * preemptable. Syncs the host's TIF_FOREIGN_FPSTATE with the KVM

 * mirror of the flag used by the hypervisor.

 */

void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)

{

	if (test_thread_flag(TIF_FOREIGN_FPSTATE))
@@ -93,10 +98,11 @@ void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu) 
}



/*

 * If the guest FPSIMD state was loaded, update the host's context

 * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu

 * so that they will be written back if the kernel clobbers them due to

 * kernel-mode NEON before re-entry into the guest.

 * Called just after exiting the guest. If the guest FPSIMD state

 * was loaded, update the host's context tracking data mark the CPU

 * FPSIMD regs as dirty and belonging to vcpu so that they will be

 * written back if the kernel clobbers them due to kernel-mode NEON

 * before re-entry into the guest.

 */

void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)

{

arch/arm64/kvm/hyp/include/hyp/switch.h

+4 −0
Original line number Diff line number Diff line
@@ -173,6 +173,8 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code) 
		return false;



	/* Valid trap.  Switch the context: */



	/* First disable enough traps to allow us to update the registers */

	if (has_vhe()) {

		reg = CPACR_EL1_FPEN;

		if (sve_guest)
@@ -188,11 +190,13 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code) 
	}

	isb();



	/* Write out the host state if it's in the registers */

	if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {

		__fpsimd_save_state(vcpu->arch.host_fpsimd_state);

		vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;

	}



	/* Restore the guest state */

	if (sve_guest)

		__hyp_sve_restore_guest(vcpu);

	else