s390/kvm: validate the floating-point control before restoring it (96b2d7a8) · Commits · 戴 / test

The kvm_arch_vcpu_load() does not validate whether the floating-point control (FPC) is valid. Further, the return code of the restore is not checked too. If the FPC is invalid, the restore fails and the host FPC value might remain. The correct behavior would be to clear the FPC if it is not valid. Hence, validate the FPC value and, optionally, reset the value before restoring it. Reviewed-by:

David Hildenbrand <dahi@linux.vnet.ibm.com> Signed-off-by:

Hendrik Brueckner <brueckner@linux.vnet.ibm.com> Signed-off-by:

Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kvm/kvm-s390.c

+8 −2

Original line number	Diff line number	Diff line
		@@ -1200,6 +1200,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)

		void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
		{
		__u32 fpc;

		save_fp_ctl(&vcpu->arch.host_fpregs.fpc);
		if (test_kvm_facility(vcpu->kvm, 129))
		save_vx_regs((__vector128 *)&vcpu->arch.host_vregs->vrs);
		@@ -1207,12 +1209,16 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
		save_fp_regs(vcpu->arch.host_fpregs.fprs);
		save_access_regs(vcpu->arch.host_acrs);
		if (test_kvm_facility(vcpu->kvm, 129)) {
		restore_fp_ctl(&vcpu->run->s.regs.fpc);
		fpc = vcpu->run->s.regs.fpc;
		restore_vx_regs((__vector128 *)&vcpu->run->s.regs.vrs);
		} else {
		restore_fp_ctl(&vcpu->arch.guest_fpregs.fpc);
		fpc = vcpu->arch.guest_fpregs.fpc;
		restore_fp_regs(vcpu->arch.guest_fpregs.fprs);
		}
		if (test_fp_ctl(fpc))
		/* User space provided an invalid FPC, let's clear it */
		fpc = 0;
		restore_fp_ctl(&fpc);
		restore_access_regs(vcpu->run->s.regs.acrs);
		gmap_enable(vcpu->arch.gmap);
		atomic_set_mask(CPUSTAT_RUNNING, &vcpu->arch.sie_block->cpuflags);

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