Mailing List Archive

[xen stable-4.16] libxl: fix guest kexec - skip cpuid policy
commit 6e081438bf8ef616d0123aab7a743476d8114ef6
Author: Jason Andryuk <>
AuthorDate: Tue Feb 7 17:06:47 2023 +0100
Commit: Jan Beulich <>
CommitDate: Tue Feb 7 17:06:47 2023 +0100

libxl: fix guest kexec - skip cpuid policy

When a domain performs a kexec (soft reset), libxl__build_pre() is
called with the existing domid. Calling libxl__cpuid_legacy() on the
existing domain fails since the cpuid policy has already been set, and
the guest isn't rebuilt and doesn't kexec.

xc: error: Failed to set d1's policy (err leaf 0xffffffff, subleaf 0xffffffff, msr 0xffffffff) (17 = File exists): Internal error
libxl: error: libxl_cpuid.c:494:libxl__cpuid_legacy: Domain 1:Failed to apply CPUID policy: File exists
libxl: error: libxl_create.c:1641:domcreate_rebuild_done: Domain 1:cannot (re-)build domain: -3
libxl: error: libxl_xshelp.c:201:libxl__xs_read_mandatory: xenstore read failed: `/libxl/1/type': No such file or directory
libxl: warning: libxl_dom.c:49:libxl__domain_type: unable to get domain type for domid=1, assuming HVM

During a soft_reset, skip calling libxl__cpuid_legacy() to avoid the
issue. Before commit 34990446ca91, the libxl__cpuid_legacy() failure
would have been ignored, so kexec would continue.

Fixes: 34990446ca91 ("libxl: don't ignore the return value from xc_cpuid_apply_policy")
Signed-off-by: Jason Andryuk <>
Reviewed-by: Anthony PERARD <>
master commit: 1e454c2b5b1172e0fc7457e411ebaba61db8fc87
master date: 2023-01-26 10:58:23 +0100
tools/libs/light/libxl_create.c | 2 ++
tools/libs/light/libxl_dom.c | 2 +-
tools/libs/light/libxl_internal.h | 1 +
3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/libs/light/libxl_create.c b/tools/libs/light/libxl_create.c
index 885675591f..2e6357a9d7 100644
--- a/tools/libs/light/libxl_create.c
+++ b/tools/libs/light/libxl_create.c
@@ -2176,6 +2176,8 @@ static int do_domain_soft_reset(libxl_ctx *ctx,
cdcs->domid_out = &domid_out;

+ state->soft_reset = true;
dom_path = libxl__xs_get_dompath(gc, domid);
if (!dom_path) {
LOGD(ERROR, domid, "failed to read domain path");
diff --git a/tools/libs/light/libxl_dom.c b/tools/libs/light/libxl_dom.c
index 73fccd9243..a2bd2395fa 100644
--- a/tools/libs/light/libxl_dom.c
+++ b/tools/libs/light/libxl_dom.c
@@ -384,7 +384,7 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
/* Construct a CPUID policy, but only for brand new domains. Domains
* being migrated-in/restored have CPUID handled during the
* static_data_done() callback. */
- if (!state->restore)
+ if (!state->restore && !state->soft_reset)
rc = libxl__cpuid_legacy(ctx, domid, false, info);

diff --git a/tools/libs/light/libxl_internal.h b/tools/libs/light/libxl_internal.h
index 0b4671318c..ee6a251700 100644
--- a/tools/libs/light/libxl_internal.h
+++ b/tools/libs/light/libxl_internal.h
@@ -1407,6 +1407,7 @@ typedef struct {
/* Whether this domain is being migrated/restored, or booting fresh. Only
* applicable to the primary domain, not support domains (e.g. stub QEMU). */
bool restore;
+ bool soft_reset;
} libxl__domain_build_state;

_hidden void libxl__domain_build_state_init(libxl__domain_build_state *s);
generated by git-patchbot for /home/xen/git/xen.git#stable-4.16