[Bug,209155] KVM Linux guest with more than 1 CPU panics after commit 404d5d7bff0d419fe11c7eaebca9ec8f25258f95 on old CPU (Phenom x4)

Commit Message

[e-mail] Sept. 10, 2020, 12:12 p.m. UTC

https://bugzilla.kernel.org/show_bug.cgi?id=209155

--- Comment #14 from Paul K. ([e-mail]) ---
I'm having a bit of a problem applying the patches cleanly. Working with both
v5.9-rc3 and 5.9-rc4 give the same:

Patch 1/3 goes fine:
$ patch -p1 < /net/phenom/export/home2/users/kronenpj/tmp/patch1-3.txt 
patching file arch/x86/kvm/svm/svm.c

Patch 2/3 fails on hunk #3:
$ patch -p1 < /net/phenom/export/home2/users/kronenpj/tmp/patch2-3.txt 
patching file arch/x86/kvm/svm/svm.c
Hunk #1 succeeded at 3349 (offset 2 lines).
Hunk #2 succeeded at 3504 (offset 4 lines).
Hunk #3 FAILED at 3533.
1 out of 3 hunks FAILED -- saving rejects to file arch/x86/kvm/svm/svm.c.rej

$ cat svm.c.rej 
        return exit_fastpath;

Adding that line manually and continuing with the third patch:
$ patch -p1 < /net/phenom/export/home2/users/kronenpj/tmp/patch3-3.txt 
patching file arch/x86/kvm/svm/svm.c
Hunk #2 succeeded at 3536 with fuzz 2 (offset 8 lines).

The patch against v5.9-rc4+ works as expected.

Patch

--- arch/x86/kvm/svm/svm.c
+++ arch/x86/kvm/svm/svm.c
@@ -3533,6 +3537,7 @@  static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu
*vcpu)
                svm_handle_mce(svm);

        svm_complete_interrupts(svm);
+       exit_fastpath = svm_exit_handlers_fastpath(vcpu);

        vmcb_mark_all_clean(svm->vmcb);