linux-kernel - Re: [PATCH v2 0/2] KVM: SVM: Virtual GIF

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Date:   Wed, 23 Aug 2017 18:37:50 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Janakarajan Natarajan <Janakarajan.Natarajan@....com>,
        kvm@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org
Cc:     Radim Krcmar <rkrcmar@...hat.com>, Joerg Roedel <joro@...tes.org>,
        Andy Lutomirski <luto@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Piotr Luc <piotr.luc@...el.com>, Borislav Petkov <bp@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Yazen Ghannam <yazen.ghannam@....com>
Subject: Re: [PATCH v2 0/2] KVM: SVM: Virtual GIF

On 23/08/2017 16:57, Janakarajan Natarajan wrote:
> This patchset adds support for the Virtual GIF (vGIF) feature. This
> feature allows the STGI and CLGI instructions to be executed in the
> Guest Mode and not require a #VMEXIT. With this, virtual interrupts
> can be controlled in the Guest Mode while still allowing physical
> interrupts to be intercepted by the hypervisor.
> 
> In order to provide this ability, two new bits are added to the VMCB
> at offset 60h:
> 
> * Bit 9	 - VGIF value
> 	 : 0 -> Virtual interrupts are masked
> 	 : 1 -> Virtual interrupts are unmasked
> 
> * Bit 25 - AMD Virtual GIF enabled for this guest
> 	 : 0 -> Disabled
> 	 : 1 -> Enabled
> 
> When a VMRUN is executed and Bit 25 is set, the processor uses Bit 9
> as the starting value of the virtual GIF. It then provides masking
> capability for when virtual interrupts are taken. Bit 9 is writeable
> by the hypervisor and loaded on VMRUN and saved on #VMEXIT. STGI/CLGI
> executed in the Guest Mode sets or clears the virtual GIF.
> 
> The advantage of this feature will be the greatly reduced number of
> world switches to support the STGI and CLGI instructions by the
> outermost hypervisor at Current Privilege Level (CPL) 0.
> 
> This has been tested with Xen, Hyper-V and KVM as the nested hypervisor.
> 
> v1->v2:
> 
> * Updated patch description and changed cpufeature definition to be similar
>   to AMD documentation.
> 
> * Updated NMI logic. STGI intercept added to assit in opening NMI window.
>   Suggested by Radim.

Applied, thanks.

Paolo

> Janakarajan Natarajan (2):
>   KVM: SVM: Add Virtual GIF feature definition
>   KVM: SVM: Enable Virtual GIF feature
> 
>  arch/x86/include/asm/cpufeatures.h |  1 +
>  arch/x86/include/asm/svm.h         |  6 ++++
>  arch/x86/kvm/svm.c                 | 62 +++++++++++++++++++++++++++++++++-----
>  3 files changed, 62 insertions(+), 7 deletions(-)
>