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Peter Anvin" , x86@kernel.org Subject: [PATCH RFC 26/39] KVM: x86/xen: grant unmap support Date: Wed, 20 Feb 2019 20:15:56 +0000 Message-Id: <20190220201609.28290-27-joao.m.martins@oracle.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20190220201609.28290-1-joao.m.martins@oracle.com> References: <20190220201609.28290-1-joao.m.martins@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9173 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=803 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902200138 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ankur Arora Grant unmap removes the grant from maptrack and marks it as not in use. We maintain a one-to-one correspondence between grant table and maptrack entries so there's no contention in allocation/free. Co-developed-by: Joao Martins Signed-off-by: Ankur Arora Signed-off-by: Joao Martins --- arch/x86/kvm/xen.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index 3603645086a7..8f06924e0dfa 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -1684,6 +1684,69 @@ static int shim_hcall_gntmap(struct kvm_xen *ld, return 0; } +static int shim_hcall_gntunmap(struct kvm_xen *xen, + struct gnttab_unmap_grant_ref *op) +{ + struct kvm_grant_map *map, unmap; + struct grant_entry_v1 **rgt; + struct grant_entry_v1 *shah; + struct kvm *rd = NULL; + domid_t domid; + u32 ref; + + domid = handle_get_domid(op->handle); + ref = handle_get_grant(op->handle); + + + rd = kvm_xen_find_vm(domid); + if (unlikely(!rd)) { + /* We already teardown all ongoing grant maps */ + op->status = GNTST_okay; + return 0; + } + + if (unlikely(ref >= gnttab_entries(rd))) { + pr_err("gnttab: bad ref %u\n", ref); + op->status = GNTST_bad_handle; + return 0; + } + + rgt = rd->arch.xen.gnttab.frames_v1; + map = maptrack_entry(rd->arch.xen.gnttab.handle, ref); + + /* + * The test_and_clear_bit (below) serializes ownership of this + * grant-entry. After we clear it, there can be a grant-map on this + * entry. So we cache the unmap entry before relinquishing ownership. + */ + unmap = *map; + + if (!test_and_clear_bit(_KVM_GNTMAP_ACTIVE, + (unsigned long *) &map->flags)) { + pr_err("gnttab: bad flags for %u (dom %u ref %u) flags %x\n", + op->handle, domid, ref, unmap.flags); + op->status = GNTST_bad_handle; + return 0; + } + + /* Give up the reference taken in get_user_pages_remote(). */ + put_page(virt_to_page(unmap.gpa)); + + shah = shared_entry(rgt, unmap.ref); + + /* + * We have cleared _KVM_GNTMAP_ACTIVE, so a simultaneous grant-map + * could update the shah and we would stomp all over it but the + * guest deserves it. + */ + if (!(unmap.flags & GNTMAP_readonly)) + clear_bit(_GTF_writing, (unsigned long *) &shah->flags); + clear_bit(_GTF_reading, (unsigned long *) &shah->flags); + + op->status = GNTST_okay; + return 0; +} + static int shim_hcall_gnttab(int op, void *p, int count) { int ret = -ENOSYS; @@ -1698,6 +1761,16 @@ static int shim_hcall_gnttab(int op, void *p, int count) ret = 0; break; } + case GNTTABOP_unmap_grant_ref: { + struct gnttab_unmap_grant_ref *ref = p; + + for (i = 0; i < count; i++) { + shim_hcall_gntunmap(xen_shim, ref + i); + ref[i].host_addr = 0; + } + ret = 0; + break; + } default: pr_info("lcall-gnttab:op default=%d\n", op); break; -- 2.11.0