-cpu haswell / broadwell have no MONITOR in features1

[Paul Goyette]

In qemu 2.9.0 if you run

    qemu-system-x86_64 -cpu Broadwell (or Haswell)

then the CPU features1 flag include the SSE3 bit, but do NOT include the MONITOR/MWAIT bit. This is so even when the host includes the features.

Additionally, running qemu in this manner results in several error messages:

warning: TCG doesn't support requested feature: CPUID.01H:ECX.fma [bit 12]
warning: TCG doesn't support requested feature: CPUID.01H:ECX.pcid [bit 17]
warning: TCG doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21]
warning: TCG doesn't support requested feature: CPUID.01H:ECX.tsc-deadline [bit 24]
warning: TCG doesn't support requested feature: CPUID.01H:ECX.avx [bit 28]
warning: TCG doesn't support requested feature: CPUID.01H:ECX.f16c [bit 29]
warning: TCG doesn't support requested feature: CPUID.01H:ECX.rdrand [bit 30]
warning: TCG doesn't support requested feature: CPUID.07H:EBX.hle [bit 4]
warning: TCG doesn't support requested feature: CPUID.07H:EBX.avx2 [bit 5]
warning: TCG doesn't support requested feature: CPUID.07H:EBX.invpcid [bit 10]
warning: TCG doesn't support requested feature: CPUID.07H:EBX.rtm [bit 11]
warning: TCG doesn't support requested feature: CPUID.07H:EBX.rdseed [bit 18]
warning: TCG doesn't support requested feature: CPUID.80000001H:ECX.3dnowprefetch

(Among possible other uses, the lack of the MONITOR feature bit causes NetBSD to fall-back on a
check-and-pause loop while an application CPU is waiting to be told to proceed by the boot CPU.)

[Thomas Huth (th-huth)]

Can you still reproduce this issue with the latest version of QEMU? Looking at https://git.qemu.org/?p=qemu.git;a=commitdiff;h=0723cc8a5558c94388 for example, it might have been fixed since QEMU v4.2...

[Paul Goyette (paul-whooppee)]

This bug seems not to be a problem, and may reflect an issue with
NetBSD. Even though the decode of the features1 register does not
include MONITOR/MWAIT, that capability is separately reported on a
separate line, further down (apologies in advance for any confusing
line-wrap):

# cpuctl identify 0
cpu0: highest basic info 0000000d
cpu0: highest hypervisor info 40000001
cpu0: highest extended info 80000008
cpu0: Running on hypervisor: QEMU(TCG)
cpu0: "Intel Core Processor (Broadwell)"
cpu0: Intel Core M-5xxx, 5th gen Core (Broadwell) (686-class), 3198.24 MHz
cpu0: family 0x6 model 0x3d stepping 0x2 (id 0x306d2)
cpu0: features 0x78bfbfd<FPU,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA>
cpu0: features 0x78bfbfd<CMOV,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2>
cpu0: features1 0xced82203<SSE3,PCLMULQDQ,SSSE3,CX16,SSE41,SSE42,MOVBE,POPCNT>
cpu0: features1 0xced82203<AES,XSAVE,OSXSAVE,RDRAND,RAZ>
cpu0: features2 0x28100800<SYSCALL/SYSRET,XD,RDTSCP,EM64T>
cpu0: features3 0x21<LAHF,LZCNT>
cpu0: features5 0x180389<FSGSBASE,BMI1,SMEP,BMI2,ERMS,ADX,SMAP>
cpu0: xsave features 0x7<x87,SSE,AVX>
cpu0: xsave instructions 0x1<XSAVEOPT>
cpu0: xsave area size: current 832, maximum 832, xgetbv enabled
cpu0: enabled xsave 0x7<x87,SSE,AVX>
cpu0: I-cache 32KB 64B/line 8-way, D-cache 32KB 64B/line 8-way
cpu0: L2 cache 4MB 64B/line 16-way
cpu0: L3 cache 16MB 64B/line 16-way
cpu0: Initial APIC ID 0
cpu0: Cluster/Package ID 0
cpu0: Core ID 0
cpu0: SMT ID 0
cpu0: MONITOR/MWAIT extensions 0x3<EMX,IBE>
cpu0: monitor-line size 0
cpu0: DSPM-eax 0x4<ARAT>
cpu0: SEF highest subleaf 00000000
cpu0: Power Management features: 0
cpu0: microcode version 0x0, platform ID 0
#

On Fri, 22 May 2020, Thomas Huth wrote:

> Can you still reproduce this issue with the latest version of QEMU?
> Looking at
> https://git.qemu.org/?p=qemu.git;a=commitdiff;h=0723cc8a5558c94388 for
> example, it might have been fixed since QEMU v4.2...
>
> ** Changed in: qemu
> Status: New => Incomplete
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1693667
>
> Title:
> -cpu haswell / broadwell have no MONITOR in features1
>
> Status in QEMU:
> Incomplete
>
> Bug description:
> In qemu 2.9.0 if you run
>
> qemu-system-x86_64 -cpu Broadwell (or Haswell)
>
> then the CPU features1 flag include the SSE3 bit, but do NOT include
> the MONITOR/MWAIT bit. This is so even when the host includes the
> features.
>
>
> Additionally, running qemu in this manner results in several error messages:
>
> warning: TCG doesn't support requested feature: CPUID.01H:ECX.fma [bit 12]
> warning: TCG doesn't support requested feature: CPUID.01H:ECX.pcid [bit 17]
> warning: TCG doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21]
> warning: TCG doesn't support requested feature: CPUID.01H:ECX.tsc-deadline [bit 24]
> warning: TCG doesn't support requested feature: CPUID.01H:ECX.avx [bit 28]
> warning: TCG doesn't support requested feature: CPUID.01H:ECX.f16c [bit 29]
> warning: TCG doesn't support requested feature: CPUID.01H:ECX.rdrand [bit 30]
> warning: TCG doesn't support requested feature: CPUID.07H:EBX.hle [bit 4]
> ...

[Launchpad Janitor (janitor)]

[Expired for QEMU because there has been no activity for 60 days.]