linux-kernel - Re: [PATCH 6/8] KVM: SVM: Report emulated SVM features to userspace

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Message-ID: <20100423142119.GF31537@amd.com>
Date:	Fri, 23 Apr 2010 16:21:19 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	Alexander Graf <agraf@...e.de>
CC:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...nel.org
Subject: Re: [PATCH 6/8] KVM: SVM: Report emulated SVM features to userspace

On Fri, Apr 23, 2010 at 03:55:15PM +0200, Alexander Graf wrote:
> 
> On 22.04.2010, at 12:33, Joerg Roedel wrote:
> > static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
> > {
> > +	switch (func) {
> > +	case 0x8000000A:
> > +		entry->eax = 1; /* SVM revision 1 */
> > +		entry->ebx = 8; /* Lets support 8 ASIDs in case we add proper
> > +				   ASID emulation to nested SVM */
> 
> I completely forgot what we do now. What do we do? It shouldn't be too
> hard to keep a table around and just assign 8 host ASIDs to the guest.
> If possible lazily, so we can just flush the whole thing when we run
> out of entries.

Currently we have no ASID emulation. We just assign a new asid at every
vmrun/vmexit. But I have a rough idea of how we can emulate ASIDs for
the L2 guest with an per-vcpu ASID cache.

> It's basically the same as my VSID mapping on ppc64 actually. See
> arch/powerpc/kvm/book3s_64_mmu_host.c and search for "slb".

Thanks, will have a look there.

> > +		entry->ecx = 0; /* Reserved */
> > +		entry->edx = 0; /* Do not support any additional features */
> 
> What about nnpt? Hasn't that been accepted yet?

I am currently working on it. If all goes well I can submit a new
version next week.

	Joerg


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