Saving/restoring the physmap to/from xenstore was introduced to
QEMU majorly in order to cover up the VRAM region restore issue.
The sequence of restore operations implies that we should know
the effective guest VRAM address *before* we have the VRAM region
restored (which happens later). Unfortunately, in Xen environment
VRAM memory does actually belong to a guest - not QEMU itself -
which means the position of this region is unknown beforehand and
can't be mapped into QEMU address space immediately.
Previously, recreating xenstore keys, holding the physmap, by the
toolstack helped to get this information in place at the right
moment ready to be consumed by QEMU to map the region properly.
The extraneous complexity of having those keys transferred by the
toolstack and unnecessary redundancy prompted us to propose a
solution which doesn't require any extra data in xenstore. The idea
is to defer the VRAM region mapping till the point we actually know
the effective address and able to map it. To that end, we initially
just skip the mapping request for the framebuffer if we unable to
map it now. Then, after the memory region restore phase, we perform
the mapping again, this time successfully, and update the VRAM region
metadata accordingly.
Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>
---
v5:
* Add an assertion and debug printf
v4:
* Use VGA post_load handler for vram_ptr update
v3:
* Modify qemu_ram_ptr_length similarly with qemu_map_ram_ptr
* Add a comment explaining qemu_map_ram_ptr and qemu_ram_ptr_length
semantic change for Xen
* Dropped some redundant changes
v2:
* Fix some building and coding style issues
---
exec.c | 16 +++++++++
hw/display/vga.c | 11 ++++++
xen-hvm.c | 104 ++++++++++---------------------------------------------
3 files changed, 46 insertions(+), 85 deletions(-)
diff --git a/exec.c b/exec.c
index aabb035..a1ac8cd 100644
--- a/exec.c
+++ b/exec.c
@@ -2008,6 +2008,14 @@ void *qemu_map_ram_ptr(RAMBlock *ram_block, ram_addr_t addr)
}
block->host = xen_map_cache(block->offset, block->max_length, 1);
+ if (block->host == NULL) {
+ /* In case we cannot establish the mapping right away we might
+ * still be able to do it later e.g. on a later stage of restore.
+ * We don't touch the block and return NULL here to indicate
+ * that intention.
+ */
+ return NULL;
+ }
}
return ramblock_ptr(block, addr);
}
@@ -2041,6 +2049,14 @@ static void *qemu_ram_ptr_length(RAMBlock *ram_block, ram_addr_t addr,
}
block->host = xen_map_cache(block->offset, block->max_length, 1);
+ if (block->host == NULL) {
+ /* In case we cannot establish the mapping right away we might
+ * still be able to do it later e.g. on a later stage of restore.
+ * We don't touch the block and return NULL here to indicate
+ * that intention.
+ */
+ return NULL;
+ }
}
return ramblock_ptr(block, addr);
diff --git a/hw/display/vga.c b/hw/display/vga.c
index 69c3e1d..7d85fd8 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -2035,6 +2035,12 @@ static int vga_common_post_load(void *opaque, int version_id)
{
VGACommonState *s = opaque;
+ if (xen_enabled() && !s->vram_ptr) {
+ /* update VRAM region pointer in case we've failed
+ * the last time during init phase */
+ s->vram_ptr = memory_region_get_ram_ptr(&s->vram);
+ assert(s->vram_ptr);
+ }
/* force refresh */
s->graphic_mode = -1;
vbe_update_vgaregs(s);
@@ -2165,6 +2171,11 @@ void vga_common_init(VGACommonState *s, Object *obj, bool global_vmstate)
vmstate_register_ram(&s->vram, global_vmstate ? NULL : DEVICE(obj));
xen_register_framebuffer(&s->vram);
s->vram_ptr = memory_region_get_ram_ptr(&s->vram);
+ /* VRAM pointer might still be NULL here if we are restoring on Xen.
+ We try to get it again later at post-load phase. */
+#ifdef DEBUG_VGA_MEM
+ printf("vga: vram ptr: %p\n", s->vram_ptr);
+#endif
s->get_bpp = vga_get_bpp;
s->get_offsets = vga_get_offsets;
s->get_resolution = vga_get_resolution;
diff --git a/xen-hvm.c b/xen-hvm.c
index 5043beb..8bedd9b 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -317,7 +317,6 @@ static int xen_add_to_physmap(XenIOState *state,
XenPhysmap *physmap = NULL;
hwaddr pfn, start_gpfn;
hwaddr phys_offset = memory_region_get_ram_addr(mr);
- char path[80], value[17];
const char *mr_name;
if (get_physmapping(state, start_addr, size)) {
@@ -340,6 +339,22 @@ go_physmap:
DPRINTF("mapping vram to %"HWADDR_PRIx" - %"HWADDR_PRIx"\n",
start_addr, start_addr + size);
+ mr_name = memory_region_name(mr);
+
+ physmap = g_malloc(sizeof(XenPhysmap));
+
+ physmap->start_addr = start_addr;
+ physmap->size = size;
+ physmap->name = mr_name;
+ physmap->phys_offset = phys_offset;
+
+ QLIST_INSERT_HEAD(&state->physmap, physmap, list);
+
+ if (runstate_check(RUN_STATE_INMIGRATE)) {
+ /* If we are migrating the region has been already mapped */
+ return 0;
+ }
+
pfn = phys_offset >> TARGET_PAGE_BITS;
start_gpfn = start_addr >> TARGET_PAGE_BITS;
for (i = 0; i < size >> TARGET_PAGE_BITS; i++) {
@@ -350,49 +365,17 @@ go_physmap:
if (rc) {
DPRINTF("add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, errno);
+
+ QLIST_REMOVE(physmap, list);
+ g_free(physmap);
return -rc;
}
}
- mr_name = memory_region_name(mr);
-
- physmap = g_malloc(sizeof (XenPhysmap));
-
- physmap->start_addr = start_addr;
- physmap->size = size;
- physmap->name = mr_name;
- physmap->phys_offset = phys_offset;
-
- QLIST_INSERT_HEAD(&state->physmap, physmap, list);
-
xc_domain_pin_memory_cacheattr(xen_xc, xen_domid,
start_addr >> TARGET_PAGE_BITS,
(start_addr + size - 1) >> TARGET_PAGE_BITS,
XEN_DOMCTL_MEM_CACHEATTR_WB);
-
- snprintf(path, sizeof(path),
- "/local/domain/0/device-model/%d/physmap/%"PRIx64"/start_addr",
- xen_domid, (uint64_t)phys_offset);
- snprintf(value, sizeof(value), "%"PRIx64, (uint64_t)start_addr);
- if (!xs_write(state->xenstore, 0, path, value, strlen(value))) {
- return -1;
- }
- snprintf(path, sizeof(path),
- "/local/domain/0/device-model/%d/physmap/%"PRIx64"/size",
- xen_domid, (uint64_t)phys_offset);
- snprintf(value, sizeof(value), "%"PRIx64, (uint64_t)size);
- if (!xs_write(state->xenstore, 0, path, value, strlen(value))) {
- return -1;
- }
- if (mr_name) {
- snprintf(path, sizeof(path),
- "/local/domain/0/device-model/%d/physmap/%"PRIx64"/name",
- xen_domid, (uint64_t)phys_offset);
- if (!xs_write(state->xenstore, 0, path, mr_name, strlen(mr_name))) {
- return -1;
- }
- }
-
return 0;
}
@@ -1152,54 +1135,6 @@ static void xen_exit_notifier(Notifier *n, void *data)
xs_daemon_close(state->xenstore);
}
-static void xen_read_physmap(XenIOState *state)
-{
- XenPhysmap *physmap = NULL;
- unsigned int len, num, i;
- char path[80], *value = NULL;
- char **entries = NULL;
-
- snprintf(path, sizeof(path),
- "/local/domain/0/device-model/%d/physmap", xen_domid);
- entries = xs_directory(state->xenstore, 0, path, &num);
- if (entries == NULL)
- return;
-
- for (i = 0; i < num; i++) {
- physmap = g_malloc(sizeof (XenPhysmap));
- physmap->phys_offset = strtoull(entries[i], NULL, 16);
- snprintf(path, sizeof(path),
- "/local/domain/0/device-model/%d/physmap/%s/start_addr",
- xen_domid, entries[i]);
- value = xs_read(state->xenstore, 0, path, &len);
- if (value == NULL) {
- g_free(physmap);
- continue;
- }
- physmap->start_addr = strtoull(value, NULL, 16);
- free(value);
-
- snprintf(path, sizeof(path),
- "/local/domain/0/device-model/%d/physmap/%s/size",
- xen_domid, entries[i]);
- value = xs_read(state->xenstore, 0, path, &len);
- if (value == NULL) {
- g_free(physmap);
- continue;
- }
- physmap->size = strtoull(value, NULL, 16);
- free(value);
-
- snprintf(path, sizeof(path),
- "/local/domain/0/device-model/%d/physmap/%s/name",
- xen_domid, entries[i]);
- physmap->name = xs_read(state->xenstore, 0, path, &len);
-
- QLIST_INSERT_HEAD(&state->physmap, physmap, list);
- }
- free(entries);
-}
-
static void xen_wakeup_notifier(Notifier *notifier, void *data)
{
xc_set_hvm_param(xen_xc, xen_domid, HVM_PARAM_ACPI_S_STATE, 0);
@@ -1339,7 +1274,6 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion **ram_memory)
goto err;
}
xen_be_register_common();
- xen_read_physmap(state);
/* Disable ACPI build because Xen handles it */
pcms->acpi_build_enabled = false;
--
2.7.4
On Wed, Mar 15, 2017 at 04:01:19PM +0000, Igor Druzhinin wrote: > Saving/restoring the physmap to/from xenstore was introduced to > QEMU majorly in order to cover up the VRAM region restore issue. > The sequence of restore operations implies that we should know > the effective guest VRAM address *before* we have the VRAM region > restored (which happens later). Unfortunately, in Xen environment > VRAM memory does actually belong to a guest - not QEMU itself - > which means the position of this region is unknown beforehand and > can't be mapped into QEMU address space immediately. > > Previously, recreating xenstore keys, holding the physmap, by the > toolstack helped to get this information in place at the right > moment ready to be consumed by QEMU to map the region properly. > > The extraneous complexity of having those keys transferred by the > toolstack and unnecessary redundancy prompted us to propose a > solution which doesn't require any extra data in xenstore. The idea > is to defer the VRAM region mapping till the point we actually know > the effective address and able to map it. To that end, we initially > just skip the mapping request for the framebuffer if we unable to > map it now. Then, after the memory region restore phase, we perform > the mapping again, this time successfully, and update the VRAM region > metadata accordingly. > > Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com> I've tried to migrate a guest with this patch, but once migrated, the screen is black (via VNC, keyboard is working fine). I haven't try to migrate a guest from QEMU without this patch to a QEMU with it. -- Anthony PERARD
On 16/03/17 12:26, Anthony PERARD wrote: > On Wed, Mar 15, 2017 at 04:01:19PM +0000, Igor Druzhinin wrote: >> Saving/restoring the physmap to/from xenstore was introduced to >> QEMU majorly in order to cover up the VRAM region restore issue. >> The sequence of restore operations implies that we should know >> the effective guest VRAM address *before* we have the VRAM region >> restored (which happens later). Unfortunately, in Xen environment >> VRAM memory does actually belong to a guest - not QEMU itself - >> which means the position of this region is unknown beforehand and >> can't be mapped into QEMU address space immediately. >> >> Previously, recreating xenstore keys, holding the physmap, by the >> toolstack helped to get this information in place at the right >> moment ready to be consumed by QEMU to map the region properly. >> >> The extraneous complexity of having those keys transferred by the >> toolstack and unnecessary redundancy prompted us to propose a >> solution which doesn't require any extra data in xenstore. The idea >> is to defer the VRAM region mapping till the point we actually know >> the effective address and able to map it. To that end, we initially >> just skip the mapping request for the framebuffer if we unable to >> map it now. Then, after the memory region restore phase, we perform >> the mapping again, this time successfully, and update the VRAM region >> metadata accordingly. >> >> Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com> > > I've tried to migrate a guest with this patch, but once migrated, the > screen is black (via VNC, keyboard is working fine). > > I haven't try to migrate a guest from QEMU without this patch to a QEMU > with it. > Hmm. It works for me - I've tried to migrate between identical QEMUs with this patch on localhost. Save/restore also works fine. What do you mean 'the screen is black'? Could you describe your actions so I could try to reproduce it? Igor
On 16/03/17 12:54, Igor Druzhinin wrote: > On 16/03/17 12:26, Anthony PERARD wrote: >> On Wed, Mar 15, 2017 at 04:01:19PM +0000, Igor Druzhinin wrote: >>> Saving/restoring the physmap to/from xenstore was introduced to >>> QEMU majorly in order to cover up the VRAM region restore issue. >>> The sequence of restore operations implies that we should know >>> the effective guest VRAM address *before* we have the VRAM region >>> restored (which happens later). Unfortunately, in Xen environment >>> VRAM memory does actually belong to a guest - not QEMU itself - >>> which means the position of this region is unknown beforehand and >>> can't be mapped into QEMU address space immediately. >>> >>> Previously, recreating xenstore keys, holding the physmap, by the >>> toolstack helped to get this information in place at the right >>> moment ready to be consumed by QEMU to map the region properly. >>> >>> The extraneous complexity of having those keys transferred by the >>> toolstack and unnecessary redundancy prompted us to propose a >>> solution which doesn't require any extra data in xenstore. The idea >>> is to defer the VRAM region mapping till the point we actually know >>> the effective address and able to map it. To that end, we initially >>> just skip the mapping request for the framebuffer if we unable to >>> map it now. Then, after the memory region restore phase, we perform >>> the mapping again, this time successfully, and update the VRAM region >>> metadata accordingly. >>> >>> Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com> >> >> I've tried to migrate a guest with this patch, but once migrated, the >> screen is black (via VNC, keyboard is working fine). >> >> I haven't try to migrate a guest from QEMU without this patch to a QEMU >> with it. >> > > Hmm. It works for me - I've tried to migrate between identical QEMUs > with this patch on localhost. Save/restore also works fine. > > What do you mean 'the screen is black'? Could you describe your actions > so I could try to reproduce it? Ok. I could track down the issue - starting from v4 the patch doesn't work for cirrus. The reason is that post_load handler is different for cirrus and doesn't call the parent handler from common vga code. I manage to fix it by updating the corresponding handler by duplicating the code. But is it a good solution? Would it be better to have the common handler called in this function instead? > > Igor > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > https://lists.xen.org/xen-devel >
On Thu, Mar 16, 2017 at 02:06:21PM +0000, Igor Druzhinin wrote: > On 16/03/17 12:54, Igor Druzhinin wrote: > > On 16/03/17 12:26, Anthony PERARD wrote: > >> I've tried to migrate a guest with this patch, but once migrated, the > >> screen is black (via VNC, keyboard is working fine). > >> > > Hmm. It works for me - I've tried to migrate between identical QEMUs > > with this patch on localhost. Save/restore also works fine. > > > Ok. I could track down the issue - starting from v4 the patch doesn't > work for cirrus. The reason is that post_load handler is different for > cirrus and doesn't call the parent handler from common vga code. > > I manage to fix it by updating the corresponding handler by duplicating > the code. But is it a good solution? Would it be better to have the > common handler called in this function instead? :(, vga_common_post_load have a misleading name. Yes, I think it would be better to have a common post_load been called by every vga cards. -- Anthony PERARD
On Thu, Mar 16, 2017 at 02:46:56PM +0000, Anthony PERARD wrote: > On Thu, Mar 16, 2017 at 02:06:21PM +0000, Igor Druzhinin wrote: > > On 16/03/17 12:54, Igor Druzhinin wrote: > > > On 16/03/17 12:26, Anthony PERARD wrote: > > >> I've tried to migrate a guest with this patch, but once migrated, the > > >> screen is black (via VNC, keyboard is working fine). > > >> > > > Hmm. It works for me - I've tried to migrate between identical QEMUs > > > with this patch on localhost. Save/restore also works fine. > > > > > Ok. I could track down the issue - starting from v4 the patch doesn't > > work for cirrus. The reason is that post_load handler is different for > > cirrus and doesn't call the parent handler from common vga code. > > > > I manage to fix it by updating the corresponding handler by duplicating > > the code. But is it a good solution? Would it be better to have the > > common handler called in this function instead? > > :(, vga_common_post_load have a misleading name. Yes, I think it would > be better to have a common post_load been called by every vga cards. The issue is probably more complicated than I thought, as vga_common_post_load is probably not called because cirrus does not use vmstate_vga_common struct. -- Anthony PERARD
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