From: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
To: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v3 01/11] KVM: MMU: avoid pte_list_desc running out in kvm_mmu_pte_write
Date: Tue, 13 Sep 2011 18:24:20 +0800 [thread overview]
Message-ID: <4E6F2F54.4030004@cn.fujitsu.com> (raw)
In-Reply-To: <4E6F2790.4020602@redhat.com>
On 09/13/2011 05:51 PM, Avi Kivity wrote:
> 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).
>
If memory is not enough, we just clear sptes on pte_write path(not prefetch spte),
the later page fault path can return -1 to let guest crash. Hmm?
next prev parent reply other threads:[~2011-09-13 10:21 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-30 2:34 [PATCH v3 01/11] KVM: MMU: avoid pte_list_desc running out in kvm_mmu_pte_write Xiao Guangrong
2011-08-30 2:34 ` [PATCH v3 02/11] KVM: x86: tag the instructions which are used to write page table Xiao Guangrong
2011-08-30 2:35 ` [PATCH v3 03/11] KVM: x86: retry non-page-table writing instruction Xiao Guangrong
2011-09-13 10:47 ` Avi Kivity
2011-09-13 18:24 ` Xiao Guangrong
2011-09-14 9:53 ` Avi Kivity
2011-09-14 10:19 ` Xiao Guangrong
2011-09-15 4:56 ` Xiao Guangrong
2011-08-30 2:35 ` [PATCH v3 04/11] KVM: x86: cleanup port-in/port-out emulated Xiao Guangrong
2011-08-30 2:35 ` [PATCH v3 05/11] KVM: MMU: do not mark accessed bit on pte write path Xiao Guangrong
2011-09-13 10:53 ` Avi Kivity
2011-09-13 18:29 ` Xiao Guangrong
2011-09-14 9:55 ` Avi Kivity
2011-09-15 13:11 ` Marcelo Tosatti
2011-08-30 2:36 ` [PATCH v3 06/11] KVM: MMU: cleanup FNAME(invlpg) Xiao Guangrong
2011-09-13 11:00 ` Avi Kivity
2011-09-13 18:31 ` Xiao Guangrong
2011-09-14 9:57 ` Avi Kivity
2011-08-30 2:36 ` [PATCH v3 07/11] KVM: MMU: fast prefetch spte on invlpg path Xiao Guangrong
2011-08-30 2:37 ` [PATCH v3 08/11] KVM: MMU: remove unnecessary kvm_mmu_free_some_pages Xiao Guangrong
2011-08-30 2:37 ` [PATCH v3 09/11] KVM: MMU: split kvm_mmu_pte_write function Xiao Guangrong
2011-08-30 2:37 ` [PATCH v3 10/11] KVM: MMU: fix detecting misaligned accessed Xiao Guangrong
2011-08-30 2:38 ` [PATCH v3 11/11] KVM: MMU: improve write flooding detected Xiao Guangrong
2011-09-13 11:07 ` Avi Kivity
2011-09-13 19:19 ` Xiao Guangrong
2011-09-14 9:59 ` Avi Kivity
2011-09-13 9:51 ` [PATCH v3 01/11] KVM: MMU: avoid pte_list_desc running out in kvm_mmu_pte_write Avi Kivity
2011-09-13 10:24 ` Xiao Guangrong [this message]
2011-09-13 10:50 ` Avi Kivity
2011-09-13 19:31 ` Xiao Guangrong
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