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

[Avi Kivity <avi@redhat.com>]

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?

!! 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).

-- 
error compiling committee.c: too many arguments to function