Re: [PATCH v2 4/6] KVM: x86: Introduce KVM_GET_SREGS2 / KVM_SET_SREGS2

From: Maxim Levitsky <mlevitsk@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org
Cc: "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jonathan Corbet <corbet@lwn.net>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>,
	"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
	<linux-kernel@vger.kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Wanpeng Li <wanpengli@tencent.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Jim Mattson <jmattson@google.com>,
	Sean Christopherson <seanjc@google.com>,
	Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH v2 4/6] KVM: x86: Introduce KVM_GET_SREGS2 / KVM_SET_SREGS2
Date: Mon, 26 Apr 2021 16:31:11 +0300	[thread overview]
Message-ID: <e887a66ea714cf244958b60e85db6f6f1336887a.camel@redhat.com> (raw)
In-Reply-To: <05161b6e-6d85-be14-9e30-e61cb742f6d0@redhat.com>

On Mon, 2021-04-26 at 15:28 +0200, Paolo Bonzini wrote:
> On 26/04/21 14:56, Maxim Levitsky wrote:
> > On Mon, 2021-04-26 at 14:32 +0200, Paolo Bonzini wrote:
> > > On 26/04/21 13:13, Maxim Levitsky wrote:
> > > > +	if (sregs2->flags & KVM_SREGS2_FLAGS_PDPTRS_VALID) {
> > > > +
> > > > +		if (!is_pae_paging(vcpu))
> > > > +			return -EINVAL;
> > > > +
> > > > +		for (i = 0 ; i < 4 ; i++)
> > > > +			kvm_pdptr_write(vcpu, i, sregs2->pdptrs[i]);
> > > > +
> > > > +		kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR);
> > > > +		mmu_reset_needed = 1;
> > > > +	}
> > > 
> > > I think this should also have
> > > 
> > > 	else {
> > > 		if (is_pae_paging(vcpu))
> > > 			return -EINVAL;
> > > 	}
> > 
> > What about the case when we migrate from qemu that doesn't use
> > this ioctl to qemu that does?
> 
> Right, that makes sense but then the "else" branch should do the same as 
> KVM_SET_SREGS.  Maybe add a "load_pdptrs" bool to __set_sregs_common?

Yes, I'll do something like that.
Thanks,
	Best regards,
		Maxim Levitsky

> 
> Paolo
>