Re: [PATCH v2] i386: Add the support for AMD EPYC 3rd generation processors

[Pankaj Gupta]

Hi Babu,

I confirm I can see both the ssbd & irbs features in guest with the
below patch. There was some issue at my end, Sorry! for the confusion.
Can you please post the official patch for inclusion.

Best regards,
Pankaj

On Mon, Mar 1, 2021 at 9:38 PM Babu Moger <babu.moger@amd.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
> > Sent: Monday, March 1, 2021 2:22 PM
> > To: Moger, Babu <Babu.Moger@amd.com>
> > Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>; Paolo Bonzini
> > <pbonzini@redhat.com>; richard.henderson@linaro.org; Eduardo Habkost
> > <ehabkost@redhat.com>; Qemu Developers <qemu-devel@nongnu.org>
> > Subject: Re: [PATCH v2] i386: Add the support for AMD EPYC 3rd generation
> > processors
> >
> > > > Hi Babu,
> > > >
> > > > I tried to test below patch for AMD EPYC Rome CPU and I got below error
> > [1]:
> > > >
> > > > Also, I noticed SSBD CPU flag for guest was still available even
> > > > without this patch, I noticed that for the guest, AMD_SSBD not got set.
> > > >
> > > > Guest:
> > > > 0x80000008 0x00: eax=0x00003028 ebx=0x00009205 ecx=0x00002003
> > > > edx=0x00000000
> > > >
> > > > [1]
> > > > [    0.008000] unchecked MSR access error: WRMSR to 0x48 (tried to
> > > > write 0x0000000000000000) at rIP: 0xffffffff9245c9e4
> > > > (native_write_msr+0x4/0x20)
> > > > [    0.008000]  [<ffffffff9243a6c5>] ? x86_spec_ctrl_setup_ap+0x35/0x50
> > > > [    0.008000]  [<ffffffff92439423>] ? identify_secondary_cpu+0x53/0x80
> > > > [    0.008000]  [<ffffffff9244adfa>] ? start_secondary+0x6a/0x1b0
> > > >
> > > > 0.011970] unchecked MSR access error: RDMSR from 0x48 at rIP:
> > > > 0xffffffff9245c772 (native_read_msr+0x2/0x40)
> > >
> > > I did not see any problem with these patches.
> > > My guest setup.
> > > # lscpu |grep -o ssbd
> > > ssbd
> > > [root@rome-vm ~]# uname -r
> > > 4.18.0-147.el8.x86_64
> > > [root@rome-vm ~]# cat /etc/redhat-release Red Hat Enterprise Linux
> > > release 8.1 (Ootpa) # wrmsr 0x48 7 [root@rome-vm ~]# rdmsr 0x48
> > > 7
> > >
> > >
> > > My host os.
> > > # uname -r
> > > 4.18.0-193.el8.x86_64
> > > [root@rome images]# cat /etc/redhat-release Red Hat Enterprise Linux
> > > release 8.2 Beta (Ootpa)
> > >
> > > Also, I only see ssbd feature when add this patch(EPYC-Rome-v2).
> > > Otherwise, I don’t see ssbd feature.
> >
> > Thanks for checking!
> > Can you also see the ibrs feature inside guest with this patch?
>
> Yes, The feature is available with this patch. Otherwise it is not available.
> [root@rome-vm ~]# lscpu |grep -o ibrs
> ibrs
>
> >
> > Thanks,
> > Pankaj
> > >
> > > Thanks
> > > Babu
> > >
> > >
> > > >
> > > > Thanks,
> > > > Pankaj
> > > >
> > > > > > It is normally added as v2 for compatibility. Like this.
> > > > >
> > > > > o.k. Thanks!
> > > > > I will test this tomorrow.
> > > > >
> > > > > >
> > > > > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c index
> > > > > > 24db7ed892..f721d0db78 100644
> > > > > > --- a/target/i386/cpu.c
> > > > > > +++ b/target/i386/cpu.c
> > > > > > @@ -4179,6 +4179,20 @@ static X86CPUDefinition builtin_x86_defs[] =
> > {
> > > > > >          .xlevel = 0x8000001E,
> > > > > >          .model_id = "AMD EPYC-Rome Processor",
> > > > > >          .cache_info = &epyc_rome_cache_info,
> > > > > > +        .versions = (X86CPUVersionDefinition[]) {
> > > > > > +            { .version = 1 },
> > > > > > +            {
> > > > > > +                .version = 2,
> > > > > > +                .props = (PropValue[]) {
> > > > > > +                    { "ibrs", "on" },
> > > > > > +                    { "amd-ssbd", "on" },
> > > > > > +                    { "model-id",
> > > > > > +                      "AMD EPYC-Rome Processor" },
> > > > > > +                    { /* end of list */ }
> > > > > > +                }
> > > > > > +            },
> > > > > > +            { /* end of list */ }
> > > > > > +        }
> > > > > >      },
> > > > > >      {
> > > > > >          .name = "EPYC-Milan",