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Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel
From: |
Paolo Bonzini |
Subject: |
Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT |
Date: |
Mon, 28 Sep 2020 18:46:31 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 |
On 28/09/20 14:42, Kang, Luwei wrote:
>> No, if a feature cannot be emulated, that means it cannot be
>> enabled unless it matches the host. That's generally not a problem
>> since Intel PT is usually used only with "-cpu host".
>>
> The limitation of LIP in qemu will mask off the Intel PT in KVM guest
> even with "-cpu host". e.g. This bit will be set in SnowRidge HW and
> later.
I agree that QEMU would have to learn about LIP. Unlike this patch,
however, x86_cpu_filter_features would have to fail if host LIP != guest
LIP. That is, something like
(ecx_0 & INTEL_PT_IP_LIP)) !=
(env->features[INTEL_PT_ECX_0] & INTEL_PT_IP_LIP)
where "intel-pt-lip" would be a feature in env->features[INTEL_PT_ECX_0].
> How about "-cpu cpu_model, +intel-pt" use case? The current value of
> Intel PT CPUID is a constant. Can we make the ICX CPUID as basic
> inforation(LIP is 0) and using "+intel-pt-lip" to make Intel PT work
> on the CPU which LIP is 1 on the host? As you mentioned before, Intel
> PT cannot be enabled in guest unless it matches the host.
Yes, this would work.
Paolo
- Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, (continued)
- Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, Eduardo Habkost, 2020/09/25
- Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, Paolo Bonzini, 2020/09/25
- Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, Eduardo Habkost, 2020/09/25
- Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, Paolo Bonzini, 2020/09/25
- RE: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, Kang, Luwei, 2020/09/28
- Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, Paolo Bonzini, 2020/09/28
- RE: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, Kang, Luwei, 2020/09/28
- Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, Eduardo Habkost, 2020/09/28
- RE: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, Kang, Luwei, 2020/09/28
- Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, Eduardo Habkost, 2020/09/28
- Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT,
Paolo Bonzini <=
- RE: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT, Kang, Luwei, 2020/09/28