[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[PULL 16/62] i386/xen: manage and save/restore Xen guest long_mode setti
From: |
Paolo Bonzini |
Subject: |
[PULL 16/62] i386/xen: manage and save/restore Xen guest long_mode setting |
Date: |
Thu, 2 Mar 2023 13:29:43 +0100 |
From: David Woodhouse <dwmw@amazon.co.uk>
Xen will "latch" the guest's 32-bit or 64-bit ("long mode") setting when
the guest writes the MSR to fill in the hypercall page, or when the guest
sets the event channel callback in HVM_PARAM_CALLBACK_IRQ.
KVM handles the former and sets the kernel's long_mode flag accordingly.
The latter will be handled in userspace. Keep them in sync by noticing
when a hypercall is made in a mode that doesn't match qemu's idea of
the guest mode, and resyncing from the kernel. Do that same sync right
before serialization too, in case the guest has set the hypercall page
but hasn't yet made a system call.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
---
hw/i386/kvm/xen_overlay.c | 62 +++++++++++++++++++++++++++++++++++++++
hw/i386/kvm/xen_overlay.h | 4 +++
target/i386/kvm/xen-emu.c | 12 ++++++++
3 files changed, 78 insertions(+)
diff --git a/hw/i386/kvm/xen_overlay.c b/hw/i386/kvm/xen_overlay.c
index a2441e2b4e4a..8685d879594e 100644
--- a/hw/i386/kvm/xen_overlay.c
+++ b/hw/i386/kvm/xen_overlay.c
@@ -44,6 +44,7 @@ struct XenOverlayState {
MemoryRegion shinfo_mem;
void *shinfo_ptr;
uint64_t shinfo_gpa;
+ bool long_mode;
};
struct XenOverlayState *xen_overlay_singleton;
@@ -96,9 +97,21 @@ static void xen_overlay_realize(DeviceState *dev, Error
**errp)
s->shinfo_ptr = memory_region_get_ram_ptr(&s->shinfo_mem);
s->shinfo_gpa = INVALID_GPA;
+ s->long_mode = false;
memset(s->shinfo_ptr, 0, XEN_PAGE_SIZE);
}
+static int xen_overlay_pre_save(void *opaque)
+{
+ /*
+ * Fetch the kernel's idea of long_mode to avoid the race condition
+ * where the guest has set the hypercall page up in 64-bit mode but
+ * not yet made a hypercall by the time migration happens, so qemu
+ * hasn't yet noticed.
+ */
+ return xen_sync_long_mode();
+}
+
static int xen_overlay_post_load(void *opaque, int version_id)
{
XenOverlayState *s = opaque;
@@ -107,6 +120,9 @@ static int xen_overlay_post_load(void *opaque, int
version_id)
xen_overlay_do_map_page(&s->shinfo_mem, s->shinfo_gpa);
xen_overlay_set_be_shinfo(s->shinfo_gpa >> XEN_PAGE_SHIFT);
}
+ if (s->long_mode) {
+ xen_set_long_mode(true);
+ }
return 0;
}
@@ -121,9 +137,11 @@ static const VMStateDescription xen_overlay_vmstate = {
.version_id = 1,
.minimum_version_id = 1,
.needed = xen_overlay_is_needed,
+ .pre_save = xen_overlay_pre_save,
.post_load = xen_overlay_post_load,
.fields = (VMStateField[]) {
VMSTATE_UINT64(shinfo_gpa, XenOverlayState),
+ VMSTATE_BOOL(long_mode, XenOverlayState),
VMSTATE_END_OF_LIST()
}
};
@@ -208,3 +226,47 @@ void *xen_overlay_get_shinfo_ptr(void)
return s->shinfo_ptr;
}
+
+int xen_sync_long_mode(void)
+{
+ int ret;
+ struct kvm_xen_hvm_attr xa = {
+ .type = KVM_XEN_ATTR_TYPE_LONG_MODE,
+ };
+
+ if (!xen_overlay_singleton) {
+ return -ENOENT;
+ }
+
+ ret = kvm_vm_ioctl(kvm_state, KVM_XEN_HVM_GET_ATTR, &xa);
+ if (!ret) {
+ xen_overlay_singleton->long_mode = xa.u.long_mode;
+ }
+
+ return ret;
+}
+
+int xen_set_long_mode(bool long_mode)
+{
+ int ret;
+ struct kvm_xen_hvm_attr xa = {
+ .type = KVM_XEN_ATTR_TYPE_LONG_MODE,
+ .u.long_mode = long_mode,
+ };
+
+ if (!xen_overlay_singleton) {
+ return -ENOENT;
+ }
+
+ ret = kvm_vm_ioctl(kvm_state, KVM_XEN_HVM_SET_ATTR, &xa);
+ if (!ret) {
+ xen_overlay_singleton->long_mode = xa.u.long_mode;
+ }
+
+ return ret;
+}
+
+bool xen_is_long_mode(void)
+{
+ return xen_overlay_singleton && xen_overlay_singleton->long_mode;
+}
diff --git a/hw/i386/kvm/xen_overlay.h b/hw/i386/kvm/xen_overlay.h
index 00cff05bb0fd..5c46a0b03659 100644
--- a/hw/i386/kvm/xen_overlay.h
+++ b/hw/i386/kvm/xen_overlay.h
@@ -17,4 +17,8 @@ void xen_overlay_create(void);
int xen_overlay_map_shinfo_page(uint64_t gpa);
void *xen_overlay_get_shinfo_ptr(void);
+int xen_sync_long_mode(void);
+int xen_set_long_mode(bool long_mode);
+bool xen_is_long_mode(void);
+
#endif /* QEMU_XEN_OVERLAY_H */
diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
index ebea27caf634..be6d85f2cb7b 100644
--- a/target/i386/kvm/xen-emu.c
+++ b/target/i386/kvm/xen-emu.c
@@ -20,6 +20,8 @@
#include "trace.h"
#include "sysemu/runstate.h"
+#include "hw/i386/kvm/xen_overlay.h"
+
#include "hw/xen/interface/version.h"
#include "hw/xen/interface/sched.h"
@@ -282,6 +284,16 @@ int kvm_xen_handle_exit(X86CPU *cpu, struct kvm_xen_exit
*exit)
return -1;
}
+ /*
+ * The kernel latches the guest 32/64 mode when the MSR is used to fill
+ * the hypercall page. So if we see a hypercall in a mode that doesn't
+ * match our own idea of the guest mode, fetch the kernel's idea of the
+ * "long mode" to remain in sync.
+ */
+ if (exit->u.hcall.longmode != xen_is_long_mode()) {
+ xen_sync_long_mode();
+ }
+
if (!do_kvm_xen_handle_exit(cpu, exit)) {
/*
* Some hypercalls will be deliberately "implemented" by returning
--
2.39.1
- [PULL 06/62] i386/kvm: Set Xen vCPU ID in KVM, (continued)
- [PULL 06/62] i386/kvm: Set Xen vCPU ID in KVM, Paolo Bonzini, 2023/03/02
- [PULL 07/62] xen-platform: exclude vfio-pci from the PCI platform unplug, Paolo Bonzini, 2023/03/02
- [PULL 08/62] xen-platform: allow its creation with XEN_EMULATE mode, Paolo Bonzini, 2023/03/02
- [PULL 09/62] i386/xen: handle guest hypercalls, Paolo Bonzini, 2023/03/02
- [PULL 10/62] i386/xen: implement HYPERVISOR_xen_version, Paolo Bonzini, 2023/03/02
- [PULL 11/62] i386/xen: implement HYPERVISOR_sched_op, SCHEDOP_shutdown, Paolo Bonzini, 2023/03/02
- [PULL 12/62] i386/xen: Implement SCHEDOP_poll and SCHEDOP_yield, Paolo Bonzini, 2023/03/02
- [PULL 13/62] hw/xen: Add xen_overlay device for emulating shared xenheap pages, Paolo Bonzini, 2023/03/02
- [PULL 15/62] i386/xen: add pc_machine_kvm_type to initialize XEN_EMULATE mode, Paolo Bonzini, 2023/03/02
- [PULL 14/62] xen: Permit --xen-domid argument when accel is KVM, Paolo Bonzini, 2023/03/02
- [PULL 16/62] i386/xen: manage and save/restore Xen guest long_mode setting,
Paolo Bonzini <=
- [PULL 19/62] i386/xen: implement HYPERVISOR_hvm_op, Paolo Bonzini, 2023/03/02
- [PULL 21/62] i386/xen: handle VCPUOP_register_vcpu_info, Paolo Bonzini, 2023/03/02
- [PULL 25/62] i386/xen: implement HVMOP_set_evtchn_upcall_vector, Paolo Bonzini, 2023/03/02
- [PULL 26/62] i386/xen: implement HVMOP_set_param, Paolo Bonzini, 2023/03/02
- [PULL 18/62] i386/xen: implement XENMEM_add_to_physmap_batch, Paolo Bonzini, 2023/03/02
- [PULL 20/62] i386/xen: implement HYPERVISOR_vcpu_op, Paolo Bonzini, 2023/03/02
- [PULL 17/62] i386/xen: implement HYPERVISOR_memory_op, Paolo Bonzini, 2023/03/02
- [PULL 36/62] hw/xen: Implement EVTCHNOP_bind_interdomain, Paolo Bonzini, 2023/03/02
- [PULL 32/62] hw/xen: Implement EVTCHNOP_bind_virq, Paolo Bonzini, 2023/03/02
- [PULL 27/62] hw/xen: Add xen_evtchn device for event channel emulation, Paolo Bonzini, 2023/03/02