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Re: [Qemu-devel] [PATCH v3 6/9] i386/cpu: Add CPUID.1F generation suppor
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCH v3 6/9] i386/cpu: Add CPUID.1F generation support for multi-dies PCMachine |
Date: |
Wed, 19 Jun 2019 20:21:37 -0300 |
I've just noticed one thing I don't understand:
On Wed, Jun 12, 2019 at 04:41:01PM +0800, Like Xu wrote:
> The CPUID.1F as Intel V2 Extended Topology Enumeration Leaf would be
> exposed if guests want to emulate multiple software-visible die within
> each package. Per Intel's SDM, the 0x1f is a superset of 0xb, thus they
> can be generated by almost same code as 0xb except die_offset setting.
>
> If the number of dies per package is less than 2, the qemu will not
> expose CPUID.1F regardless of whether the host supports CPUID.1F.
>
> Signed-off-by: Like Xu <address@hidden>
> ---
> target/i386/cpu.c | 37 +++++++++++++++++++++++++++++++++++++
> target/i386/cpu.h | 4 ++++
> target/i386/kvm.c | 12 ++++++++++++
> 3 files changed, 53 insertions(+)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 09e20a2c3b..127aff74a6 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -4437,6 +4437,42 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
> uint32_t count,
> *ecx |= CPUID_TOPOLOGY_LEVEL_INVALID;
> }
>
> + assert(!(*eax & ~0x1f));
> + *ebx &= 0xffff; /* The count doesn't need to be reliable. */
> + break;
> + case 0x1F:
> + /* V2 Extended Topology Enumeration Leaf */
> + if (env->nr_dies < 2 || !cpu->enable_cpuid_0x1f) {
> + *eax = *ebx = *ecx = *edx = 0;
Why exactly do you need cpu->enable_cpuid_0x1f? When would it
make sense to set dies > 1 but disable CPUID.1F?
> + break;
> + }
[...]
--
Eduardo
- [Qemu-devel] [PATCH v3 2/9] hw/i386: Adjust nr_dies with configured smp_dies for PCMachine, (continued)
- [Qemu-devel] [PATCH v3 2/9] hw/i386: Adjust nr_dies with configured smp_dies for PCMachine, Like Xu, 2019/06/12
- [Qemu-devel] [PATCH v3 5/9] tests/x86-cpuid: Update testcases in test_topo_bits() with multiple dies, Like Xu, 2019/06/12
- [Qemu-devel] [PATCH v3 3/9] i386/cpu: Consolidate die-id validity in smp context, Like Xu, 2019/06/12
- [Qemu-devel] [PATCH v3 4/9] i386: Update new x86_apicid parsing rules with die_offset support, Like Xu, 2019/06/12
- [Qemu-devel] [PATCH v3 6/9] i386/cpu: Add CPUID.1F generation support for multi-dies PCMachine, Like Xu, 2019/06/12
- [Qemu-devel] [PATCH v3 8/9] machine: Refactor smp_parse() in vl.c as MachineClass::smp_parse(), Like Xu, 2019/06/12
- [Qemu-devel] [PATCH v3 9/9] vl.c: Add -smp, dies=* command line support and update doc, Like Xu, 2019/06/12
- [Qemu-devel] [PATCH v3 1/9] i386: Add die-level cpu topology to x86CPU on PCMachine, Like Xu, 2019/06/12
- Re: [Qemu-devel] [PATCH v3 0/9] Introduce cpu die topology and enable CPUID.1F for i386, Like Xu, 2019/06/18