Re: [PATCHv2 3/4] Add HYPER-V apic access MSRs.

[Vadim Rozenfeld <vrozenfe@redhat.com>]

On Sun, 2010-01-17 at 14:20 +0200, Avi Kivity wrote:
> On 01/17/2010 11:03 AM, Gleb Natapov wrote:
> 
> > Signed-off-by: Gleb Natapov<gleb@redhat.com>
> > Signed-off-by: Vadim Rozenfeld<vrozenfe@redhat.com>
> >    
> 
> Changelog entry.
> 
> >
> >   struct kvm_mem_alias {
> > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> > index ba8c045..4b224f9 100644
> > --- a/arch/x86/kvm/lapic.c
> > +++ b/arch/x86/kvm/lapic.c
> > @@ -1246,3 +1246,34 @@ int kvm_x2apic_msr_read(struct kvm_vcpu *vcpu, u32 msr, u64 *data)
> >
> >   	return 0;
> >   }
> > +
> > +int kvm_hv_vapic_msr_write(struct kvm_vcpu *vcpu, u32 reg, u64 data)
> > +{
> > +	struct kvm_lapic *apic = vcpu->arch.apic;
> > +
> > +	if (!irqchip_in_kernel(vcpu->kvm))
> > +		return 1;
> > +
> > +	/* if this is ICR write vector before command */
> > +	if (reg == APIC_ICR)
> > +		apic_reg_write(apic, APIC_ICR2, (u32)(data>>  32));
> > +	return apic_reg_write(apic, reg, (u32)data);
> > +}
> > +
> > +int kvm_hv_vapic_msr_read(struct kvm_vcpu *vcpu, u32 reg, u64 *data)
> > +{
> > +	struct kvm_lapic *apic = vcpu->arch.apic;
> > +	u32 low, high = 0;
> > +
> > +	if (!irqchip_in_kernel(vcpu->kvm))
> > +		return 1;
> > +
> > +	if (apic_reg_read(apic, reg, 4,&low))
> > +		return 1;
> > +	if (reg == APIC_ICR)
> > +		apic_reg_read(apic, APIC_ICR2, 4,&high);
> > +
> > +	*data = (((u64)high)<<  32) | low;
> > +
> > +	return 0;
> > +}
> >    
> 
> I prefer putting this in x86.c (maybe later split into hyperv.c).
> 
> > diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> > index 40010b0..d081cb6 100644
> > --- a/arch/x86/kvm/lapic.h
> > +++ b/arch/x86/kvm/lapic.h
> > @@ -48,4 +48,12 @@ void kvm_lapic_sync_to_vapic(struct kvm_vcpu *vcpu);
> >
> >   int kvm_x2apic_msr_write(struct kvm_vcpu *vcpu, u32 msr, u64 data);
> >   int kvm_x2apic_msr_read(struct kvm_vcpu *vcpu, u32 msr, u64 *data);
> > +
> > +int kvm_hv_vapic_msr_write(struct kvm_vcpu *vcpu, u32 msr, u64 data);
> > +int kvm_hv_vapic_msr_read(struct kvm_vcpu *vcpu, u32 msr, u64 *data);
> > +
> > +static inline bool kvm_hv_vapic_enabled(struct kvm_vcpu *vcpu)
> > +{
> > +	return !!(vcpu->arch.hv_vapic&  HV_X64_MSR_APIC_ASSIST_PAGE_ENABLE);
> > +}
> >    
> 
> Are you sure that vapic enabled is equivalent to apic assist page enable?
At least, when it is disable, the EOI interception mechanism won't
work.   
> 
> !! not required.
> 
> >   #endif
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index db0b2b1..2fe555c 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -632,6 +632,7 @@ static u32 msrs_to_save[] = {
> >   #endif
> >   	MSR_IA32_TSC, MSR_IA32_PERF_STATUS, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA,
> >   	HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
> > +	HV_X64_MSR_APIC_ASSIST_PAGE,
> >   };
> >
> >    
> 
> Will be dropped by msr validation.
> 
> >   static unsigned num_msrs_to_save;
> > @@ -1063,10 +1064,37 @@ static int set_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> >
> >   static int set_msr_hyperv(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> >   {
> > -	pr_unimpl(vcpu, "HYPER-V unimplemented wrmsr: 0x%x data 0x%llx\n",
> > -		  msr, data);
> > +	switch (msr) {
> > +	case HV_X64_MSR_APIC_ASSIST_PAGE: {
> > +		unsigned long vaddr;
> > +		void *addr;
> > +		struct page *page;
> > +		vcpu->arch.hv_vapic = data;
> > +		if (!kvm_hv_vapic_enabled(vcpu))
> > +			break;
> > +		vaddr = gfn_to_hva(vcpu->kvm, data>>
> > +				  HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT);
> > +		if (kvm_is_error_hva(vaddr))
> > +			return 1;
> > +		page = virt_to_page(vaddr);
> >    
> 
> virt_to_page() takes a kernel address, not a user address.  This is 
> get_user_pages().  But I think the whole thing is done better with 
> put_user().
> 
> > +		addr = kmap_atomic(page, KM_USER0);
> > +		clear_user_page(addr, vaddr, page);
> > +		kunmap_atomic(addr, KM_USER0);
> >    
> 
> Surprising that clear_user_page needs kmap_atomic() (but true).
>