linux-kernel - Re: [PATCH 06/13] KVM: x86: pass the whole hflags field to emulator and back

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Message-ID: <jpgmw1hirbw.fsf@redhat.com>
Date:	Wed, 06 May 2015 12:49:39 -0400
From:	Bandan Das <bsd@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	rkrcmar@...hat.com, guangrong.xiao@...ux.intel.com,
	Yang Zhang <yang.z.zhang@...el.com>, wanpeng.li@...ux.intel.com
Subject: Re: [PATCH 06/13] KVM: x86: pass the whole hflags field to emulator and back

Paolo Bonzini <pbonzini@...hat.com> writes:

> On 05/05/2015 17:47, Bandan Das wrote:
>> > The hflags field will contain information about system management mode
>> > and will be useful for the emulator.  Pass the entire field rather than
>> > just the guest-mode information.
>>
>> With respect to maintaining maximum isolation between vcpu internals and
>> the emulator,
>
> Isolation is maintained.  hflags are simply parts of the processor state
> that are not visible to the guest, you can choose to include them as
> separate flags or in a single one.  Bundling them in a single flag makes
> it a bit faster to pass around many of them.
>
> While we do not need all of them in the emulator, that's in some cases a
> limitation of the emulator.  For example, if we wanted to emulate
> CLGI/STGI we would need either HF_GIF_MASK or another .  Likewise,
> HF_NMI_MASK could replace emulator_set_nmi_mask (especially in v2 of the
> series, which will add kvm_set_hflags).
>
> However, if you prefer, I can change it to "bool smm_mode" + a new
> smm_exit emulator callback.

No, this makes sense. It's better to just pass hflags then to pass
bits individually.

> Paolo
>
>> why not just "bool smm_mode" ?
>> 
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