linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Paolo Bonzini <pbonzini@redhat.com>
To: "Tian, Kevin" <kevin.tian@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Zhong, Yang" <yang.zhong@intel.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"bp@alien8.de" <bp@alien8.de>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>
Cc: "Christopherson,, Sean" <seanjc@google.com>,
	"Nakajima, Jun" <jun.nakajima@intel.com>,
	"jing2.liu@linux.intel.com" <jing2.liu@linux.intel.com>,
	"Liu, Jing2" <jing2.liu@intel.com>
Subject: Re: [PATCH 15/19] kvm: x86: Save and restore guest XFD_ERR properly
Date: Sun, 12 Dec 2021 10:10:19 +0100	[thread overview]
Message-ID: <a2e954bf-22bc-669b-e39e-dd941d330fa1@redhat.com> (raw)
In-Reply-To: <BL1PR11MB5271FDCE84F4D25D0241D5998C739@BL1PR11MB5271.namprd11.prod.outlook.com>

On 12/12/21 02:50, Tian, Kevin wrote:
>>
>> If there are other XFD controlled facilities in the future, then it will
>> be NR_USED_XFD_CONTROLLED_FACILITIES * 2 VMEXITs per thread which
>> uses
>> them. Not the end of the world either.
>>
>> Looking at the targeted application space it's pretty unlikely that
>> tasks which utilize AMX are going to be so short lived that the overhead
>> of these VMEXITs really matters.
>>
>> This of course can be revisited when there is a sane use case, but
>> optimizing for it prematurely does not buy us anything else than
>> pointless complexity.
> It may affect guest which still uses CR0.TS to do lazy save. But likely
> modern OSes all move to eager save approach so always trapping #NM
> should be fine.

You also don't need to trap #NM if CPUID includes no dynamic bits, 
because then XFD will never be nonzero.

Paolo

  reply	other threads:[~2021-12-12  9:10 UTC|newest]

Thread overview: 80+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-08  0:03 [PATCH 00/19] AMX Support in KVM Yang Zhong
2021-12-08  0:03 ` [PATCH 01/19] x86/fpu: Extend prctl() with guest permissions Yang Zhong
2021-12-14  0:16   ` Thomas Gleixner
2021-12-08  0:03 ` [PATCH 02/19] x86/fpu: Prepare KVM for dynamically enabled states Yang Zhong
2021-12-13  9:12   ` Paolo Bonzini
2021-12-13 12:00     ` Thomas Gleixner
2021-12-13 12:45       ` Paolo Bonzini
2021-12-13 19:50         ` Thomas Gleixner
2021-12-08  0:03 ` [PATCH 03/19] kvm: x86: Fix xstate_required_size() to follow XSTATE alignment rule Yang Zhong
2021-12-08  0:03 ` [PATCH 04/19] kvm: x86: Check guest xstate permissions when KVM_SET_CPUID2 Yang Zhong
2021-12-08  0:03 ` [PATCH 05/19] x86/fpu: Move xfd initialization out of __fpstate_reset() to the callers Yang Zhong
2021-12-10 22:33   ` Thomas Gleixner
2021-12-08  0:03 ` [PATCH 06/19] x86/fpu: Add reallocation mechanims for KVM Yang Zhong
2021-12-08  0:03 ` [PATCH 07/19] kvm: x86: Propagate fpstate reallocation error to userspace Yang Zhong
2021-12-10 15:44   ` Paolo Bonzini
2021-12-08  0:03 ` [PATCH 08/19] x86/fpu: Move xfd_update_state() to xstate.c and export symbol Yang Zhong
2021-12-10 22:44   ` Thomas Gleixner
2021-12-08  0:03 ` [PATCH 09/19] kvm: x86: Prepare reallocation check Yang Zhong
2021-12-13  9:16   ` Paolo Bonzini
2021-12-14  7:06     ` Tian, Kevin
2021-12-14 10:16       ` Paolo Bonzini
2021-12-14 14:41         ` Liu, Jing2
2021-12-15  7:09           ` Tian, Kevin
2021-12-08  0:03 ` [PATCH 10/19] kvm: x86: Emulate WRMSR of guest IA32_XFD Yang Zhong
2021-12-10 16:02   ` Paolo Bonzini
2021-12-13  7:51     ` Liu, Jing2
2021-12-13  9:01       ` Paolo Bonzini
2021-12-14 10:26     ` Yang Zhong
2021-12-14 11:24       ` Paolo Bonzini
2021-12-10 23:09   ` Thomas Gleixner
2021-12-13 15:06   ` Paolo Bonzini
2021-12-13 19:45     ` Thomas Gleixner
2021-12-13 21:23       ` Thomas Gleixner
2021-12-14  7:16         ` Tian, Kevin
2021-12-08  0:03 ` [PATCH 11/19] kvm: x86: Check fpstate reallocation in XSETBV emulation Yang Zhong
2021-12-08  0:03 ` [PATCH 12/19] x86/fpu: Prepare KVM for bringing XFD state back in-sync Yang Zhong
2021-12-10 23:11   ` Thomas Gleixner
2021-12-08  0:03 ` [PATCH 13/19] kvm: x86: Disable WRMSR interception for IA32_XFD on demand Yang Zhong
2021-12-08  7:23   ` Liu, Jing2
2021-12-08  0:03 ` [PATCH 14/19] x86/fpu: Prepare for KVM XFD_ERR handling Yang Zhong
2021-12-10 16:16   ` Paolo Bonzini
2021-12-10 23:20   ` Thomas Gleixner
2021-12-08  0:03 ` [PATCH 15/19] kvm: x86: Save and restore guest XFD_ERR properly Yang Zhong
2021-12-10 16:23   ` Paolo Bonzini
2021-12-10 22:01   ` Paolo Bonzini
2021-12-12 13:10     ` Yang Zhong
2021-12-11  0:10   ` Thomas Gleixner
2021-12-11  1:31     ` Paolo Bonzini
2021-12-11  3:23       ` Tian, Kevin
2021-12-11 13:10       ` Thomas Gleixner
2021-12-11  3:07     ` Tian, Kevin
2021-12-11 13:29       ` Thomas Gleixner
2021-12-12  1:50         ` Tian, Kevin
2021-12-12  9:10           ` Paolo Bonzini [this message]
2021-12-08  0:03 ` [PATCH 16/19] kvm: x86: Introduce KVM_{G|S}ET_XSAVE2 ioctl Yang Zhong
2021-12-10 16:25   ` Paolo Bonzini
2021-12-10 16:30   ` Paolo Bonzini
2021-12-10 22:13     ` Paolo Bonzini
2021-12-13  8:23       ` Wang, Wei W
2021-12-13  9:24         ` Paolo Bonzini
2021-12-14  6:06           ` Wang, Wei W
2021-12-14  6:18             ` Paolo Bonzini
2021-12-15  2:39               ` Wang, Wei W
2021-12-15 13:42                 ` Paolo Bonzini
2021-12-16  8:25                   ` Wang, Wei W
2021-12-16 10:28                     ` Paolo Bonzini
2021-12-20 17:54       ` State Component 18 and Palette 1 (Re: [PATCH 16/19] kvm: x86: Introduce KVM_{G|S}ET_XSAVE2 ioctl) Nakajima, Jun
2021-12-22 14:44         ` Paolo Bonzini
2021-12-22 23:47           ` Nakajima, Jun
2021-12-22 14:52         ` Dave Hansen
2021-12-22 23:51           ` Nakajima, Jun
2021-12-13 10:10     ` [PATCH 16/19] kvm: x86: Introduce KVM_{G|S}ET_XSAVE2 ioctl Thomas Gleixner
2021-12-13 10:43       ` Paolo Bonzini
2021-12-13 12:40         ` Thomas Gleixner
2021-12-08  0:03 ` [PATCH 17/19] docs: virt: api.rst: Document the new KVM_{G, S}ET_XSAVE2 ioctls Yang Zhong
2021-12-08  0:03 ` [PATCH 18/19] kvm: x86: AMX XCR0 support for guest Yang Zhong
2021-12-10 16:30   ` Paolo Bonzini
2021-12-08  0:03 ` [PATCH 19/19] kvm: x86: Add AMX CPUIDs support Yang Zhong
2021-12-10 21:52   ` Paolo Bonzini
2021-12-11 21:20 ` [PATCH 00/19] AMX Support in KVM Thomas Gleixner

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=a2e954bf-22bc-669b-e39e-dd941d330fa1@redhat.com \
    --to=pbonzini@redhat.com \
    --cc=bp@alien8.de \
    --cc=dave.hansen@linux.intel.com \
    --cc=jing2.liu@intel.com \
    --cc=jing2.liu@linux.intel.com \
    --cc=jun.nakajima@intel.com \
    --cc=kevin.tian@intel.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=seanjc@google.com \
    --cc=tglx@linutronix.de \
    --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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).