linux-kernel - Re: [PATCH v3 01/11] KVM: MMU: avoid pte_list_desc running out in kvm_mmu_pte

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Message-ID: <4E6F2790.4020602@redhat.com>
Date:	Tue, 13 Sep 2011 12:51:12 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v3 01/11] KVM: MMU: avoid pte_list_desc running out in
 kvm_mmu_pte_write

On 08/30/2011 05:34 AM, Xiao Guangrong wrote:
> kvm_mmu_pte_write is unsafe since we need to alloc pte_list_desc in the
> function when spte is prefetched, unfortunately, we can not know how many
> spte need to be prefetched on this path, that means we can use out of the
> free  pte_list_desc object in the cache, and BUG_ON() is triggered, also some
> path does not fill the cache, such as INS instruction emulated that does not
> trigger page fault
>
> @@ -3716,10 +3735,6 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code,
>   		goto out;
>   	}
>
> -	r = mmu_topup_memory_caches(vcpu);
> -	if (r)
> -		goto out;
> -
>   	er = x86_emulate_instruction(vcpu, cr2, 0, insn, insn_len);
>

Suppose we are out of memory, can't this get us in an endless loop?

return -ENOMEM breaks as out (and kills the guest, likely).

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

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