[Qemu-devel] [PATCH for-2.9 v3 0/3] Use non-blacklisted family/model/stepping for Haswell CPU model

[Eduardo Habkost <ehabkost@redhat.com>]

I plan to merge this bug fix into 2.9.

Changes v2 -> v3:
* Rebase to latest master
* Don't touch max_x86_cpu_initfn() to reduce risk post
  hard freeze

Changes v1 -> v2:
* Coding style fixes
* Make series simpler:
  * Don't use trick: char vendor[static (CPUID_VENDOR_SZ + 1)]
    because it confuses checkpatch.pl
  * Removed patch "Add explicit array size to x86_cpu_vendor_words2str()"
* Rebased on top of my x86-next branch:
  https://github.com/ehabkost/qemu x86-next

Git branch for testing:
  https://github.com/ehabkost/qemu-hacks work/x86-rtm-blacklist

Diff from v1:

  diff --git a/target/i386/cpu.h b/target/i386/cpu.h
  index cd94726e43..647435a1d9 100644
  --- a/target/i386/cpu.h
  +++ b/target/i386/cpu.h
  @@ -1431,7 +1431,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
   void cpu_clear_apic_feature(CPUX86State *env);
   void host_cpuid(uint32_t function, uint32_t count,
                   uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t *edx);
  -void host_vendor_fms(char vendor[static (CPUID_VENDOR_SZ + 1)], int *family, int *model, int *stepping);
  +void host_vendor_fms(char *vendor, int *family, int *model, int *stepping);

   /* helper.c */
   int x86_cpu_handle_mmu_fault(CPUState *cpu, vaddr addr,
  diff --git a/target/i386/cpu.c b/target/i386/cpu.c
  index 25c6c5e115..eab1ad7935 100644
  --- a/target/i386/cpu.c
  +++ b/target/i386/cpu.c
  @@ -682,7 +682,7 @@ void host_cpuid(uint32_t function, uint32_t count,
           *edx = vec[3];
   }

  -void host_vendor_fms(char vendor[static (CPUID_VENDOR_SZ + 1)], int *family, int *model, int *stepping)
  +void host_vendor_fms(char *vendor, int *family, int *model, int *stepping)
   {
       uint32_t eax, ebx, ecx, edx;

  @@ -1570,7 +1570,8 @@ static void host_x86_cpu_class_init(ObjectClass *oc, void *data)
       xcc->kvm_required = true;
       xcc->ordering = 9;

  -    host_vendor_fms(host_cpudef.vendor, &host_cpudef.family, &host_cpudef.model, &host_cpudef.stepping);
  +    host_vendor_fms(host_cpudef.vendor, &host_cpudef.family,
  +                    &host_cpudef.model, &host_cpudef.stepping);

       cpu_x86_fill_model_id(host_cpudef.model_id);

---

A recent glibc commit[1] added a blacklist to ensure it won't use
TSX on hosts that are known to have a broken TSX implementation.

Our existing Haswell CPU model has a blacklisted
family/model/stepping combination, so it has to be updated to
make sure guests will really use TSX. This is done by patch 5/5.

However, to do this safely we need to ensure the host CPU is not
a blacklisted one, so we won't mislead guests by exposing
known-to-be-good FMS values on a known-to-be-broken host. This is
done by patch 3/5.

[1] https://sourceware.org/git/?p=glibc.git;a=commit;h=2702856bf45c82cf8e69f2064f5aa15c0ceb6359

---
Cc: dgilbert@redhat.com
Cc: fweimer@redhat.com
Cc: carlos@redhat.com
Cc: triegel@redhat.com
Cc: berrange@redhat.com
Cc: jdenemar@redhat.com
Cc: pbonzini@redhat.com

Eduardo Habkost (3):
  i386: host_vendor_fms() helper function
  i386/kvm: Blacklist TSX on known broken hosts
  i386: Change stepping of Haswell to non-blacklisted value

 include/hw/i386/pc.h |  5 +++++
 target/i386/cpu.h    |  1 +
 target/i386/cpu.c    | 21 ++++++++++++++++++++-
 target/i386/kvm.c    | 17 +++++++++++++++++
 4 files changed, 43 insertions(+), 1 deletion(-)

-- 
2.11.0.259.g40922b1