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From: Eduardo Habkost <ehabkost@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	"Kang, Luwei" <luwei.kang@intel.com>,
	"Strong, Beeman" <beeman.strong@intel.com>,
	"rth@twiddle.net" <rth@twiddle.net>
Subject: Re: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT
Date: Fri, 25 Sep 2020 16:29:56 -0400	[thread overview]
Message-ID: <20200925202956.GV3717385@habkost.net> (raw)
In-Reply-To: <036ba624-670c-d6b7-721c-ad5c9d648c1f@redhat.com>

On Fri, Sep 25, 2020 at 10:23:49PM +0200, Paolo Bonzini wrote:
> On 25/09/20 18:54, Eduardo Habkost wrote:
> > On Fri, Sep 25, 2020 at 04:42:26PM +0000, Strong, Beeman wrote:
> >> LIP=0 will differ from LIP=1 behavior only when CSbase is non-zero, which requires 32-bit code.  In that case a LIP=0 implementation will provide only the EIP offset from CSbase in IP packets (like TIP or FUP), while LIP=1 implementation will provide the full LIP (CSbase + EIP offset).
> >>
> > Thanks.  Is it possible to make KVM emulate LIP=0 behavior
> > correctly on LIP=1 hosts, or vice versa?
> 
> No, it's not possible.  KVM doesn't have a say on what the processor
> writes in the tracing packets.

Can KVM refuse to enable packet generation if CSbase is not zero
and CPUID.(EAX=14H,ECX=0)[bit 31] seen by guest is different from
host?

-- 
Eduardo



  reply	other threads:[~2020-09-25 20:31 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-24 21:38 [PATCH v1 0/3] Remove the limitation of Intel PT CPUID info Luwei Kang
2020-02-24 21:38 ` [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT Luwei Kang
2020-09-25 16:15   ` Eduardo Habkost
2020-09-25 16:42     ` Strong, Beeman
2020-09-25 16:54       ` Eduardo Habkost
2020-09-25 20:23         ` Paolo Bonzini
2020-09-25 20:29           ` Eduardo Habkost [this message]
2020-09-25 20:40             ` Paolo Bonzini
2020-09-28  5:19               ` Kang, Luwei
2020-09-28  7:35                 ` Paolo Bonzini
2020-09-28 12:42                   ` Kang, Luwei
2020-09-28 14:12                     ` Eduardo Habkost
2020-09-29  2:28                       ` Kang, Luwei
2020-09-29  3:44                         ` Eduardo Habkost
2020-09-28 16:46                     ` Paolo Bonzini
2020-09-29  2:28                       ` Kang, Luwei
2020-02-24 21:38 ` [PATCH v1 2/3] i386: Remove the CPUID limitation of " Luwei Kang
2020-02-24 21:38 ` [PATCH v1 3/3] i386: Mark the 'INTEL_PT' CPUID bit as unmigratable Luwei Kang
2020-03-30  9:56 ` [PATCH v1 0/3] Remove the limitation of Intel PT CPUID info Kang, Luwei
2020-09-18 22:02   ` Eduardo Habkost
2020-09-21  7:49     ` Kang, Luwei
2020-09-21 16:50       ` Eduardo Habkost
2020-09-23  2:52         ` Kang, Luwei
2020-09-23 14:15           ` Eduardo Habkost
2020-09-24 12:47             ` Kang, Luwei
2020-09-24 13:34               ` Eduardo Habkost
2020-09-25  8:20                 ` Kang, Luwei

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