All of lore.kernel.org
 help / color / mirror / Atom feed
From: "Tian, Kevin" <kevin.tian@intel.com>
To: "Christopherson,, Sean" <seanjc@google.com>,
	"Liu, Jing2" <jing2.liu@intel.com>
Cc: "x86@kernel.org" <x86@kernel.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	"linux-kselftest@vger.kernel.org"
	<linux-kselftest@vger.kernel.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"bp@alien8.de" <bp@alien8.de>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"corbet@lwn.net" <corbet@lwn.net>,
	"shuah@kernel.org" <shuah@kernel.org>,
	"Nakajima, Jun" <jun.nakajima@intel.com>,
	"jing2.liu@linux.intel.com" <jing2.liu@linux.intel.com>,
	"Zeng, Guang" <guang.zeng@intel.com>,
	"Wang, Wei W" <wei.w.wang@intel.com>,
	"Zhong, Yang" <yang.zhong@intel.com>
Subject: RE: [PATCH v3 22/22] kvm: x86: Disable interception for IA32_XFD on demand
Date: Wed, 29 Dec 2021 07:16:10 +0000	[thread overview]
Message-ID: <BN9PR11MB5276CE5635898CE13BFC57FC8C449@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: Ycu0KVq9PfuygKKx@google.com

> From: Tian, Kevin
> Sent: Wednesday, December 29, 2021 11:35 AM
> >
> > Speaking of nested, interception of #NM in
> vmx_update_exception_bitmap()
> > is wrong
> > with respect to nested guests.  Until XFD is supported for L2, which I didn't
> > see
> > in this series, #NM should not be intercepted while L2 is running.
> 
> Can you remind what additional thing is required to support XFD for L2?

ok, at least we require additional work on when to disable write interception.
It can be done only when both L0 and L1 make the same decision, just like 
what we did for many other VMCS settings...

> If only about performance I prefer to the current conservative approach
> as the first step. As explained earlier, #NM should be rare if the guest
> doesn't run AMX applications at all. Adding nested into this picture doesn't
> make things a lot worser.

All your comments incorporated except this one. As said always trapping
#NM for L2 is not a big problem, as long as it's rare and don't break function.
Usually a relatively static scheme is safer than a dynamic one in case of
anything overlooked for the initial implementation. 😊

Thanks
Kevin

  parent reply	other threads:[~2021-12-29  7:18 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-22 12:40 [PATCH v3 00/22] AMX Support in KVM Jing Liu
2021-12-22 12:40 ` [PATCH v3 01/22] x86/fpu: Extend fpu_xstate_prctl() with guest permissions Jing Liu
2021-12-22 12:40 ` [PATCH v3 02/22] x86/fpu: Prepare guest FPU for dynamically enabled FPU features Jing Liu
2021-12-22 12:40 ` [PATCH v3 03/22] kvm: x86: Fix xstate_required_size() to follow XSTATE alignment rule Jing Liu
2021-12-22 12:40 ` [PATCH v3 04/22] kvm: x86: Exclude unpermitted xfeatures at KVM_GET_SUPPORTED_CPUID Jing Liu
2021-12-22 12:40 ` [PATCH v3 05/22] kvm: x86: Check permitted dynamic xfeatures at KVM_SET_CPUID2 Jing Liu
2021-12-28 23:38   ` Sean Christopherson
2021-12-29  2:18     ` Tian, Kevin
2021-12-22 12:40 ` [PATCH v3 06/22] x86/fpu: Make XFD initialization in __fpstate_reset() a function argument Jing Liu
2021-12-22 12:40 ` [PATCH v3 07/22] x86/fpu: Add guest support to xfd_enable_feature() Jing Liu
2021-12-22 12:40 ` [PATCH v3 08/22] x86/fpu: Provide fpu_update_guest_perm_features() for guest Jing Liu
2021-12-22 12:40 ` [PATCH v3 09/22] kvm: x86: Enable dynamic XSAVE features at KVM_SET_CPUID2 Jing Liu
2021-12-28 23:54   ` Sean Christopherson
2021-12-29  2:23     ` Tian, Kevin
2021-12-22 12:40 ` [PATCH v3 10/22] x86/fpu: Provide fpu_update_guest_xfd() for IA32_XFD emulation Jing Liu
2021-12-22 12:40 ` [PATCH v3 11/22] kvm: x86: Add emulation for IA32_XFD Jing Liu
2021-12-22 12:40 ` [PATCH v3 12/22] x86/fpu: Prepare xfd_err in struct fpu_guest Jing Liu
2021-12-22 12:40 ` [PATCH v3 13/22] kvm: x86: Intercept #NM for saving IA32_XFD_ERR Jing Liu
2021-12-29  0:09   ` Sean Christopherson
2021-12-29  2:52     ` Tian, Kevin
2021-12-29 17:37       ` Sean Christopherson
2021-12-29  6:50     ` Tian, Kevin
2021-12-29  8:13     ` Tian, Kevin
2021-12-22 12:40 ` [PATCH v3 14/22] kvm: x86: Emulate IA32_XFD_ERR for guest Jing Liu
2021-12-22 12:40 ` [PATCH v3 15/22] kvm: x86: Disable RDMSR interception of IA32_XFD_ERR Jing Liu
2021-12-22 12:40 ` [PATCH v3 16/22] kvm: x86: Add XCR0 support for Intel AMX Jing Liu
2021-12-29  0:21   ` Sean Christopherson
2021-12-29  3:01     ` Tian, Kevin
2021-12-22 12:40 ` [PATCH v3 17/22] kvm: x86: Add CPUID " Jing Liu
2021-12-22 12:40 ` [PATCH v3 18/22] x86/fpu: Add uabi_size to guest_fpu Jing Liu
2021-12-22 12:40 ` [PATCH v3 19/22] kvm: x86: Get/set expanded xstate buffer Jing Liu
2021-12-29  0:38   ` Sean Christopherson
2021-12-29  2:57     ` Wang, Wei W
2021-12-29  6:36       ` Tian, Kevin
2021-12-22 12:40 ` [PATCH v3 20/22] kvm: selftests: Add support for KVM_CAP_XSAVE2 Jing Liu
2021-12-22 12:40 ` [PATCH v3 21/22] x86/fpu: Provide fpu_sync_guest_vmexit_xfd_state() Jing Liu
2021-12-22 12:40 ` [PATCH v3 22/22] kvm: x86: Disable interception for IA32_XFD on demand Jing Liu
2021-12-29  1:04   ` Sean Christopherson
2021-12-29  3:35     ` Tian, Kevin
2021-12-29  7:16     ` Tian, Kevin [this message]
2021-12-29 17:26       ` Sean Christopherson
2021-12-30  1:28         ` Tian, Kevin
2021-12-30  7:04         ` Tian, Kevin
2021-12-31  9:42         ` Tian, Kevin
2021-12-29  7:37     ` Tian, Kevin
2022-01-04 18:32     ` Paolo Bonzini
2022-01-04 18:58       ` Sean Christopherson

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=BN9PR11MB5276CE5635898CE13BFC57FC8C449@BN9PR11MB5276.namprd11.prod.outlook.com \
    --to=kevin.tian@intel.com \
    --cc=bp@alien8.de \
    --cc=corbet@lwn.net \
    --cc=dave.hansen@linux.intel.com \
    --cc=guang.zeng@intel.com \
    --cc=jing2.liu@intel.com \
    --cc=jing2.liu@linux.intel.com \
    --cc=jun.nakajima@intel.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-kselftest@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=pbonzini@redhat.com \
    --cc=seanjc@google.com \
    --cc=shuah@kernel.org \
    --cc=tglx@linutronix.de \
    --cc=wei.w.wang@intel.com \
    --cc=x86@kernel.org \
    --cc=yang.zhong@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.