17.09.2024 19:00, Vitaly Kuznetsov пишет:
Putting HYPERV_FEAT_SYNDBG entry under "#ifdef CONFIG_SYNDBG" in
'kvm_hyperv_properties' array is wrong: as HYPERV_FEAT_SYNDBG is not
the highest feature number, the result is an empty (zeroed) entry in
the array (and not a skipped entry!). hyperv_feature_supported() is
designed to check that all CPUID bits are set but for a zeroed
feature in 'kvm_hyperv_properties' it returns 'true' so QEMU considers
HYPERV_FEAT_SYNDBG as always supported, regardless of whether KVM host
actually supports it.
To fix the issue, leave HYPERV_FEAT_SYNDBG's definition in
'kvm_hyperv_properties' array, there's nothing wrong in having it defined
even when 'CONFIG_SYNDBG' is not set. Instead, put "hv-syndbg" CPU property
under '#ifdef CONFIG_SYNDBG' to alter the existing behavior when the flag
is silently skipped in !CONFIG_SYNDBG builds.
Leave an 'assert' sentinel in hyperv_feature_supported() making sure there
are no 'holes' or improperly defined features in 'kvm_hyperv_properties'.
Fixes: d8701185f40c ("hw: hyperv: Initial commit for Synthetic Debugging
device")
Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index ada581c5d6ea..4009fcfd6b29 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
...
@@ -3924,13 +3929,11 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
kvm_msr_entry_add(cpu, HV_X64_MSR_TSC_EMULATION_STATUS,
env->msr_hv_tsc_emulation_status);
}
-#ifdef CONFIG_SYNDBG
if (hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNDBG) &&
has_msr_hv_syndbg_options) {
kvm_msr_entry_add(cpu, HV_X64_MSR_SYNDBG_OPTIONS,
hyperv_syndbg_query_options());
}
-#endif
This change broke a minimal build:
$ ../configure --without-default-features --without-default-devices
--target-list=x86_64-softmmu --enable-kvm
...
FAILED: qemu-system-x86_64
cc -m64 @qemu-system-x86_64.rsp
/usr/bin/ld: libqemu-x86_64-softmmu.a.p/target_i386_kvm_kvm.c.o: in function
`kvm_put_msrs':
target/i386/kvm/kvm.c:4039:(.text+0x83ae): undefined reference to
`hyperv_syndbg_query_options'
collect2: error: ld returned 1 exit status
Why this particular #ifdef has been removed?
Thanks,
/mjt
