KVM: x86/xen: add support for 32-bit guests in SCHEDOP_poll

This patch introduces compat version of struct sched_poll for
SCHEDOP_poll sub-operation of sched_op hypercall, reads correct amount
of data (16 bytes in 32-bit case, 24 bytes otherwise) by using new
compat_sched_poll struct, copies it to sched_poll properly, and lets
rest of the code run as is.

Signed-off-by: Metin Kaya <metikaya@amazon.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 9187d024d006678e8d33ad8c1960099b5f9e5f8e..3e434dc339fb500ad1a81649f19aa1645a64fed9 100644 (file)
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1201,20 +1201,45 @@ static bool kvm_xen_schedop_poll(struct kvm_vcpu *vcpu, bool longmode,
        evtchn_port_t port, *ports;
        gpa_t gpa;
 
-       if (!longmode || !lapic_in_kernel(vcpu) ||
+       if (!lapic_in_kernel(vcpu) ||
            !(vcpu->kvm->arch.xen_hvm_config.flags & KVM_XEN_HVM_CONFIG_EVTCHN_SEND))
                return false;
 
        idx = srcu_read_lock(&vcpu->kvm->srcu);
        gpa = kvm_mmu_gva_to_gpa_system(vcpu, param, NULL);
        srcu_read_unlock(&vcpu->kvm->srcu, idx);
-
-       if (!gpa || kvm_vcpu_read_guest(vcpu, gpa, &sched_poll,
-                                       sizeof(sched_poll))) {
+       if (!gpa) {
                *r = -EFAULT;
                return true;
        }
 
+       if (IS_ENABLED(CONFIG_64BIT) && !longmode) {
+               struct compat_sched_poll sp32;
+
+               /* Sanity check that the compat struct definition is correct */
+               BUILD_BUG_ON(sizeof(sp32) != 16);
+
+               if (kvm_vcpu_read_guest(vcpu, gpa, &sp32, sizeof(sp32))) {
+                       *r = -EFAULT;
+                       return true;
+               }
+
+               /*
+                * This is a 32-bit pointer to an array of evtchn_port_t which
+                * are uint32_t, so once it's converted no further compat
+                * handling is needed.
+                */
+               sched_poll.ports = (void *)(unsigned long)(sp32.ports);
+               sched_poll.nr_ports = sp32.nr_ports;
+               sched_poll.timeout = sp32.timeout;
+       } else {
+               if (kvm_vcpu_read_guest(vcpu, gpa, &sched_poll,
+                                       sizeof(sched_poll))) {
+                       *r = -EFAULT;
+                       return true;
+               }
+       }
+
        if (unlikely(sched_poll.nr_ports > 1)) {
                /* Xen (unofficially) limits number of pollers to 128 */
                if (sched_poll.nr_ports > 128) {

diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h
index 8503d2c6891e3b1e6bebfa1bf0ac16a322920a52..ea33d80a0c51f811278541b428ba93ccb203a718 100644 (file)
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h
@@ -207,4 +207,11 @@ struct compat_vcpu_runstate_info {
     uint64_t time[4];
 } __attribute__((packed));
 
+struct compat_sched_poll {
+       /* This is actually a guest virtual address which points to ports. */
+       uint32_t ports;
+       unsigned int nr_ports;
+       uint64_t timeout;
+};
+
 #endif /* __ARCH_X86_KVM_XEN_H__ */