linux-kernel - Re: [kvm-devel] [PATCH 7/8] MMU: add TDP support to the KVM MMU

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Date:	Thu, 07 Feb 2008 16:04:54 +0200
From:	Izik Eidus <izike@...ranet.com>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	Avi Kivity <avi@...ranet.com>, kvm-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [kvm-devel] [PATCH 7/8] MMU: add TDP support to the KVM MMU

Joerg Roedel wrote:
> On Thu, Feb 07, 2008 at 03:27:19PM +0200, Izik Eidus wrote:
>   
>> Joerg Roedel wrote:
>>     
>>> This patch contains the changes to the KVM MMU necessary for support of the
>>> Nested Paging feature in AMD Barcelona and Phenom Processors.
>>>  
>>>       
>> good patch, it look like things will be very fixable with it
>>
>>     
>>> Signed-off-by: Joerg Roedel <joerg.roedel@....com>
>>> ---
>>> arch/x86/kvm/mmu.c |   79 ++++++++++++++++++++++++++++++++++++++++++++++++++--
>>> arch/x86/kvm/mmu.h |    6 ++++
>>> 2 files changed, 82 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>>> index 5e76963..5304d55 100644
>>> --- a/arch/x86/kvm/mmu.c
>>> +++ b/arch/x86/kvm/mmu.c
>>> @@ -1081,6 +1081,7 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
>>> 	int i;
>>> 	gfn_t root_gfn;
>>> 	struct kvm_mmu_page *sp;
>>> +	int metaphysical = 0;
>>>  	root_gfn = vcpu->arch.cr3 >> PAGE_SHIFT;
>>> @@ -1089,14 +1090,20 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
>>> 		hpa_t root = vcpu->arch.mmu.root_hpa;
>>>  		ASSERT(!VALID_PAGE(root));
>>> +		if (tdp_enabled)
>>> +			metaphysical = 1;
>>> 		sp = kvm_mmu_get_page(vcpu, root_gfn, 0,
>>> -				      PT64_ROOT_LEVEL, 0, ACC_ALL, NULL, NULL);
>>> +				      PT64_ROOT_LEVEL, metaphysical,
>>> +				      ACC_ALL, NULL, NULL);
>>> 		root = __pa(sp->spt);
>>> 		++sp->root_count;
>>> 		vcpu->arch.mmu.root_hpa = root;
>>> 		return;
>>> 	}
>>> #endif
>>> +	metaphysical = !is_paging(vcpu);
>>> +	if (tdp_enabled)
>>> +		metaphysical = 1;
>>> 	for (i = 0; i < 4; ++i) {
>>> 		hpa_t root = vcpu->arch.mmu.pae_root[i];
>>> @@ -1110,7 +1117,7 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
>>> 		} else if (vcpu->arch.mmu.root_level == 0)
>>> 			root_gfn = 0;
>>> 		sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30,
>>> -				      PT32_ROOT_LEVEL, !is_paging(vcpu),
>>> +				      PT32_ROOT_LEVEL, metaphysical,
>>> 				      ACC_ALL, NULL, NULL);
>>> 		root = __pa(sp->spt);
>>> 		++sp->root_count;
>>> @@ -1144,6 +1151,36 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
>>> 			     error_code & PFERR_WRITE_MASK, gfn);
>>> }
>>> +static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
>>> +				u32 error_code)
>>>  
>>>       
>> you probably mean gpa_t ?
>>     
>
> Yes. But the function is assigned to a function pointer. And the type of
> that pointer expects gva_t there. So I named the parameter gpa to
> describe that a guest physical address is meant there.
>
>   
>>> +{
>>> +	struct page *page;
>>> +	int r;
>>> +
>>> +	ASSERT(vcpu);
>>> +	ASSERT(VALID_PAGE(vcpu->arch.mmu.root_hpa));
>>> +
>>> +	r = mmu_topup_memory_caches(vcpu);
>>> +	if (r)
>>> +		return r;
>>> +
>>> +	down_read(&current->mm->mmap_sem);
>>> +	page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);
>>> +	if (is_error_page(page)) {
>>> +		kvm_release_page_clean(page);
>>> +		up_read(&current->mm->mmap_sem);
>>> +		return 1;
>>> +	}
>>>  
>>>       
>> i dont know if it worth checking it here,
>> in the worth case we will map the error page and the host will be safe
>>     
>
> Looking at the nonpaging_map function it is the right place to check for
> the error page.
>   

thinking about it again you are right, (for some reason i was thinking 
about old kvm code that was replace already)
the is_error_page should be here.

> Joerg Roedel
>
>   


-- 
woof.

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