Commit f88fb133 authored by Tony Krowiak's avatar Tony Krowiak Committed by Heiko Carstens
Browse files

s390/vfio-ap: make sure nib is shared 



Since the NIB is visible by HW, KVM and the (PV) guest it needs to be
in non-secure or secure but shared storage. Return code 6 is used to
indicate to a PV guest that its NIB would be on secure, unshared
storage and therefore the NIB address is invalid.

Unfortunately we have no easy way to check if a page is unshared after
vfio_pin_pages() since it will automatically export an unshared page
if the UV pin shared call did not succeed due to a page being in
unshared state.

Therefore we use the fact that UV pinning it a second time is a nop
but trying to pin an exported page is an error (0x102). If we
encounter this error, we do a vfio unpin and import the page again,
since vfio_pin_pages() exported it.

Signed-off-by: default avatarJanosch Frank <frankja@linux.ibm.com>
Signed-off-by: default avatarTony Krowiak <akrowiak@linux.ibm.com>
Acked-by: default avatarHalil Pasic <pasic@linux.ibm.com>
Tested-by: default avatarViktor Mihajlovski <mihajlov@linux.ibm.com>
Link: https://lore.kernel.org/r/20230815184333.6554-13-akrowiak@linux.ibm.com


Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent fb5040ef

drivers/s390/crypto/vfio_ap_ops.c

+30 −0
Original line number Diff line number Diff line
@@ -359,6 +359,28 @@ static int vfio_ap_validate_nib(struct kvm_vcpu *vcpu, dma_addr_t *nib) 
	return 0;

}



static int ensure_nib_shared(unsigned long addr, struct gmap *gmap)

{

	int ret;



	/*

	 * The nib has to be located in shared storage since guest and

	 * host access it. vfio_pin_pages() will do a pin shared and

	 * if that fails (possibly because it's not a shared page) it

	 * calls export. We try to do a second pin shared here so that

	 * the UV gives us an error code if we try to pin a non-shared

	 * page.

	 *

	 * If the page is already pinned shared the UV will return a success.

	 */

	ret = uv_pin_shared(addr);

	if (ret) {

		/* vfio_pin_pages() likely exported the page so let's re-import */

		gmap_convert_to_secure(gmap, addr);

	}

	return ret;

}



/**

 * vfio_ap_irq_enable - Enable Interruption for a APQN

 *
@@ -422,6 +444,14 @@ static struct ap_queue_status vfio_ap_irq_enable(struct vfio_ap_queue *q, 
	h_nib = page_to_phys(h_page) | (nib & ~PAGE_MASK);

	aqic_gisa.gisc = isc;



	/* NIB in non-shared storage is a rc 6 for PV guests */

	if (kvm_s390_pv_cpu_is_protected(vcpu) &&

	    ensure_nib_shared(h_nib & PAGE_MASK, kvm->arch.gmap)) {

		vfio_unpin_pages(&q->matrix_mdev->vdev, nib, 1);

		status.response_code = AP_RESPONSE_INVALID_ADDRESS;

		return status;

	}



	nisc = kvm_s390_gisc_register(kvm, isc);

	if (nisc < 0) {

		VFIO_AP_DBF_WARN("%s: gisc registration failed: nisc=%d, isc=%d, apqn=%#04x\n",