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From: "Tian, Kevin" <kevin.tian@intel.com>
To: Paolo Bonzini <pbonzini@redhat.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: "seanjc@google.com" <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: Sat, 11 Dec 2021 03:23:23 +0000	[thread overview]
Message-ID: <BN9PR11MB52764C77E9BF0E44C27265838C729@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <87c26050-9242-e6fb-3fce-b6bde815f76a@redhat.com>

> From: Paolo Bonzini
> Sent: Saturday, December 11, 2021 9:32 AM
> 
> On 12/11/21 01:10, Thomas Gleixner wrote:
> >      2) When the guest triggers #NM is takes an VMEXIT and the host
> >         does:
> >
> >                  rdmsrl(MSR_XFD_ERR, vcpu->arch.guest_fpu.xfd_err);
> >
> >         injects the #NM and goes on.
> >
> >      3) When the guest writes to MSR_XFD_ERR it takes an VMEXIT and
> >         the host does:
> >
> >             vcpu->arch.guest_fpu.xfd_err = msrval;
> >             wrmsrl(MSR_XFD_ERR, msrval);
> 
> No wrmsrl here I think, the host value is 0 and should stay so.  Instead
> the wrmsrl will happen the next time the VCPU loop is entred.
> 

To elaborate I guess the reason is because MSR_XFD_ERR should 
always contain host value 0 after preemption is enabled, while 
WRMSR emulation is called with preemption enabled. Then we 
just need wait for the next time the vcpu loop is entered to 
restore the guest value after preemption is disabled. 😊

Thanks
Kevin

  reply	other threads:[~2021-12-11  3:23 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 [this message]
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
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

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