[xen stable-4.16] libxl: fix guest kexec - skip cpuid policy

[patchbot@xxxxxxx]

commit 6e081438bf8ef616d0123aab7a743476d8114ef6
Author:     Jason Andryuk <jandryuk@xxxxxxxxx>
AuthorDate: Tue Feb 7 17:06:47 2023 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
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 <jandryuk@xxxxxxxxx>
    Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
    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,
                               aop_console_how);
     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);
 
 out:
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