Re: [Qemu-devel] [PATCH v2] target/i386: Introduce Denverton CPU model

[Eduardo Habkost]

On Wed, Jul 17, 2019 at 01:39:01PM +0800, Tao Xu wrote:
> Hi Eduardo,
> 
> Could I ask a question about introducing a old CPU model? Maybe not so old
> because it was launched in 2017. It is the former generation (Atom Server)
> of Snowridge and if this cpu model be added, qemu may can migrate guest
> between Denverton CPU and Snowridge CPU.
> 
> I am wondering which way is more appropriate, because maybe there are a few
> Denverton machines using old microcodes:
> 
> 1. Just like this patch, introduce one version cpu cpu model.
> 
> 2. Introduce multi versions of cpu model, cover old microcodes, may be 3
> versions.

What exactly are the differences between the old and new
microcodes?  Is it always possible to install a new microcode on
machines that are not up to date?

Both options look good to me.  I think it's OK to just declare
old microcode versions as not supported by QEMU, but I won't
complain if you decide to add multiple versions.

> 
> On 7/17/2019 12:57 PM, Tao Xu wrote:
> > Denverton is the Atom Processor of Intel Harrisonville platform.
> > 
> > For more information:
> > https://ark.intel.com/content/www/us/en/ark/products/\
> > codename/63508/denverton.html
> > 
> > Signed-off-by: Tao Xu <address@hidden>
> > ---
> > 
> > Changes in v2:
> > 
> >      - Renamed as Denverton instead of Denverton-Server, because there
> >        is only server for Denverton
> >      - Remove vmx from cpu model
> > ---
> >   target/i386/cpu.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 45 insertions(+)
> > 
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index 805ce95247..38000dd975 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -2471,6 +2471,51 @@ static X86CPUDefinition builtin_x86_defs[] = {
> >           .xlevel = 0x80000008,
> >           .model_id = "Intel Xeon Processor (Icelake)",
> >       },
> > +    {
> > +        .name = "Denverton",
> > +        .level = 21,
> > +        .vendor = CPUID_VENDOR_INTEL,
> > +        .family = 6,
> > +        .model = 95,
> > +        .stepping = 1,
> > +        .features[FEAT_1_EDX] =
> > +            CPUID_FP87 | CPUID_VME | CPUID_DE | CPUID_PSE | CPUID_TSC |
> > +            CPUID_MSR | CPUID_PAE | CPUID_MCE | CPUID_CX8 | CPUID_APIC |
> > +            CPUID_SEP | CPUID_MTRR | CPUID_PGE | CPUID_MCA | CPUID_CMOV |
> > +            CPUID_PAT | CPUID_PSE36 | CPUID_CLFLUSH | CPUID_MMX | 
> > CPUID_FXSR |
> > +            CPUID_SSE | CPUID_SSE2,
> > +        .features[FEAT_1_ECX] =
> > +            CPUID_EXT_SSE3 | CPUID_EXT_PCLMULQDQ | CPUID_EXT_MONITOR |
> > +            CPUID_EXT_SSSE3 | CPUID_EXT_CX16 | CPUID_EXT_SSE41 |
> > +            CPUID_EXT_SSE42 | CPUID_EXT_X2APIC | CPUID_EXT_MOVBE |
> > +            CPUID_EXT_POPCNT | CPUID_EXT_TSC_DEADLINE_TIMER |
> > +            CPUID_EXT_AES | CPUID_EXT_XSAVE | CPUID_EXT_RDRAND,
> > +        .features[FEAT_8000_0001_EDX] =
> > +            CPUID_EXT2_SYSCALL | CPUID_EXT2_NX | CPUID_EXT2_PDPE1GB |
> > +            CPUID_EXT2_RDTSCP | CPUID_EXT2_LM,
> > +        .features[FEAT_8000_0001_ECX] =
> > +            CPUID_EXT3_LAHF_LM | CPUID_EXT3_3DNOWPREFETCH,
> > +        .features[FEAT_7_0_EBX] =
> > +            CPUID_7_0_EBX_FSGSBASE | CPUID_7_0_EBX_SMEP | 
> > CPUID_7_0_EBX_ERMS |
> > +            CPUID_7_0_EBX_MPX | CPUID_7_0_EBX_RDSEED | CPUID_7_0_EBX_SMAP |
> > +            CPUID_7_0_EBX_CLFLUSHOPT | CPUID_7_0_EBX_SHA_NI,
> > +        .features[FEAT_7_0_EDX] =
> > +            CPUID_7_0_EDX_SPEC_CTRL | CPUID_7_0_EDX_ARCH_CAPABILITIES |
> > +            CPUID_7_0_EDX_SPEC_CTRL_SSBD,
> > +        /*
> > +         * Missing: XSAVES (not supported by some Linux versions,
> > +         * including v4.1 to v4.12).
> > +         * KVM doesn't yet expose any XSAVES state save component,
> > +         * and the only one defined in Skylake (processor tracing)
> > +         * probably will block migration anyway.
> > +         */
> > +        .features[FEAT_XSAVE] =
> > +            CPUID_XSAVE_XSAVEOPT | CPUID_XSAVE_XSAVEC | 
> > CPUID_XSAVE_XGETBV1,
> > +        .features[FEAT_6_EAX] =
> > +            CPUID_6_EAX_ARAT,
> > +        .xlevel = 0x80000008,
> > +        .model_id = "Intel Atom Processor (Denverton)",
> > +    },
> >       {
> >           .name = "SnowRidge-Server",
> >           .level = 27,
> > --
> > 2.20.1
> > 
> > 
> 

-- 
Eduardo