Commit 75236f5f authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: SEV: Return appropriate error codes if SEV-ES scratch setup fails 



Return appropriate error codes if setting up the GHCB scratch area for an
SEV-ES guest fails.  In particular, returning -EINVAL instead of -ENOMEM
when allocating the kernel buffer could be confusing as userspace would
likely suspect a guest issue.

Fixes: 8f423a80 ("KVM: SVM: Support MMIO for an SEV-ES guest")
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20211109222350.2266045-2-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent a955cad8

arch/x86/kvm/svm/sev.c

+17 −13
Original line number Diff line number Diff line
@@ -2530,7 +2530,7 @@ void pre_sev_run(struct vcpu_svm *svm, int cpu) 
}



#define GHCB_SCRATCH_AREA_LIMIT		(16ULL * PAGE_SIZE)

static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)

static int setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)

{

	struct vmcb_control_area *control = &svm->vmcb->control;

	struct ghcb *ghcb = svm->sev_es.ghcb;
@@ -2541,14 +2541,14 @@ static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len) 
	scratch_gpa_beg = ghcb_get_sw_scratch(ghcb);

	if (!scratch_gpa_beg) {

		pr_err("vmgexit: scratch gpa not provided\n");

		return false;

		return -EINVAL;

	}



	scratch_gpa_end = scratch_gpa_beg + len;

	if (scratch_gpa_end < scratch_gpa_beg) {

		pr_err("vmgexit: scratch length (%#llx) not valid for scratch address (%#llx)\n",

		       len, scratch_gpa_beg);

		return false;

		return -EINVAL;

	}



	if ((scratch_gpa_beg & PAGE_MASK) == control->ghcb_gpa) {
@@ -2566,7 +2566,7 @@ static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len) 
		    scratch_gpa_end > ghcb_scratch_end) {

			pr_err("vmgexit: scratch area is outside of GHCB shared buffer area (%#llx - %#llx)\n",

			       scratch_gpa_beg, scratch_gpa_end);

			return false;

			return -EINVAL;

		}



		scratch_va = (void *)svm->sev_es.ghcb;
@@ -2579,18 +2579,18 @@ static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len) 
		if (len > GHCB_SCRATCH_AREA_LIMIT) {

			pr_err("vmgexit: scratch area exceeds KVM limits (%#llx requested, %#llx limit)\n",

			       len, GHCB_SCRATCH_AREA_LIMIT);

			return false;

			return -EINVAL;

		}

		scratch_va = kzalloc(len, GFP_KERNEL_ACCOUNT);

		if (!scratch_va)

			return false;

			return -ENOMEM;



		if (kvm_read_guest(svm->vcpu.kvm, scratch_gpa_beg, scratch_va, len)) {

			/* Unable to copy scratch area from guest */

			pr_err("vmgexit: kvm_read_guest for scratch area failed\n");



			kfree(scratch_va);

			return false;

			return -EFAULT;

		}



		/*
@@ -2606,7 +2606,7 @@ static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len) 
	svm->sev_es.ghcb_sa = scratch_va;

	svm->sev_es.ghcb_sa_len = len;



	return true;

	return 0;

}



static void set_ghcb_msr_bits(struct vcpu_svm *svm, u64 value, u64 mask,
@@ -2745,10 +2745,10 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu) 
	ghcb_set_sw_exit_info_1(ghcb, 0);

	ghcb_set_sw_exit_info_2(ghcb, 0);



	ret = -EINVAL;

	switch (exit_code) {

	case SVM_VMGEXIT_MMIO_READ:

		if (!setup_vmgexit_scratch(svm, true, control->exit_info_2))

		ret = setup_vmgexit_scratch(svm, true, control->exit_info_2);

		if (ret)

			break;



		ret = kvm_sev_es_mmio_read(vcpu,
@@ -2757,7 +2757,8 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu) 
					   svm->sev_es.ghcb_sa);

		break;

	case SVM_VMGEXIT_MMIO_WRITE:

		if (!setup_vmgexit_scratch(svm, false, control->exit_info_2))

		ret = setup_vmgexit_scratch(svm, false, control->exit_info_2);

		if (ret)

			break;



		ret = kvm_sev_es_mmio_write(vcpu,
@@ -2800,6 +2801,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu) 
		vcpu_unimpl(vcpu,

			    "vmgexit: unsupported event - exit_info_1=%#llx, exit_info_2=%#llx\n",

			    control->exit_info_1, control->exit_info_2);

		ret = -EINVAL;

		break;

	default:

		ret = svm_invoke_exit_handler(vcpu, exit_code);
@@ -2812,6 +2814,7 @@ int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in) 
{

	int count;

	int bytes;

	int r;



	if (svm->vmcb->control.exit_info_2 > INT_MAX)

		return -EINVAL;
@@ -2820,8 +2823,9 @@ int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in) 
	if (unlikely(check_mul_overflow(count, size, &bytes)))

		return -EINVAL;



	if (!setup_vmgexit_scratch(svm, in, bytes))

		return -EINVAL;

	r = setup_vmgexit_scratch(svm, in, bytes);

	if (r)

		return r;



	return kvm_sev_es_string_io(&svm->vcpu, size, port, svm->sev_es.ghcb_sa,

				    count, in);