From: "Huang, Kai" <kai.huang@intel.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>, <kvm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, Yan Zhao <yan.y.zhao@intel.com>,
Isaku Yamahata <isaku.yamahata@intel.com>,
Michael Roth <michael.roth@amd.com>,
Yu Zhang <yu.c.zhang@linux.intel.com>,
Chao Peng <chao.p.peng@linux.intel.com>,
Fuad Tabba <tabba@google.com>,
"David Matlack" <dmatlack@google.com>
Subject: Re: [PATCH 11/16] KVM: x86/mmu: Explicitly disallow private accesses to emulated MMIO
Date: Fri, 8 Mar 2024 13:09:22 +1300 [thread overview]
Message-ID: <d0390205-e083-44e7-8046-f5754dd3bf06@intel.com> (raw)
In-Reply-To: <3acw6nkfyre4t46i5gmd4lzxxlveiaksp55hunidfhi6lr6brh@7oqn63pu3flb>
On 8/03/2024 6:10 am, Kirill A. Shutemov wrote:
> On Thu, Mar 07, 2024 at 11:49:11AM +1300, Huang, Kai wrote:
>>
>>
>> On 7/03/2024 11:43 am, Sean Christopherson wrote:
>>> On Thu, Mar 07, 2024, Kai Huang wrote:
>>>>
>>>>
>>>> On 28/02/2024 3:41 pm, Sean Christopherson wrote:
>>>>> Explicitly detect and disallow private accesses to emulated MMIO in
>>>>> kvm_handle_noslot_fault() instead of relying on kvm_faultin_pfn_private()
>>>>> to perform the check. This will allow the page fault path to go straight
>>>>> to kvm_handle_noslot_fault() without bouncing through __kvm_faultin_pfn().
>>>>>
>>>>> Signed-off-by: Sean Christopherson <seanjc@google.com>
>>>>> ---
>>>>> arch/x86/kvm/mmu/mmu.c | 5 +++++
>>>>> 1 file changed, 5 insertions(+)
>>>>>
>>>>> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
>>>>> index 5c8caab64ba2..ebdb3fcce3dc 100644
>>>>> --- a/arch/x86/kvm/mmu/mmu.c
>>>>> +++ b/arch/x86/kvm/mmu/mmu.c
>>>>> @@ -3314,6 +3314,11 @@ static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
>>>>> {
>>>>> gva_t gva = fault->is_tdp ? 0 : fault->addr;
>>>>> + if (fault->is_private) {
>>>>> + kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
>>>>> + return -EFAULT;
>>>>> + }
>>>>> +
>>>>
>>>> As mentioned in another reply in this series, unless I am mistaken, for TDX
>>>> guest the _first_ MMIO access would still cause EPT violation with MMIO GFN
>>>> being private.
>>>>
>>>> Returning to userspace cannot really help here because the MMIO mapping is
>>>> inside the guest.
>>>
>>> That's a guest bug. The guest *knows* it's a TDX VM, it *has* to know. Accessing
>>> emulated MMIO and thus taking a #VE before enabling paging is nonsensical. Either
>>> enable paging and setup MMIO regions as shared, or go straight to TDCALL.
>>
>> +Kirill,
>>
>> I kinda forgot the detail, but what I am afraid is there might be bunch of
>> existing TDX guests (since TDX guest code is upstream-ed) using unmodified
>> drivers, which doesn't map MMIO regions as shared I suppose.
>
> Unmodified drivers gets their MMIO regions mapped with ioremap() that sets
> shared bit, unless asked explicitly to make it private (encrypted).
>
Thanks for clarification. Obviously I had bad memory.
next prev parent reply other threads:[~2024-03-08 0:09 UTC|newest]
Thread overview: 83+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-28 2:41 [PATCH 00/16] KVM: x86/mmu: Page fault and MMIO cleanups Sean Christopherson
2024-02-28 2:41 ` [PATCH 01/16] KVM: x86/mmu: Exit to userspace with -EFAULT if private fault hits emulation Sean Christopherson
2024-03-01 8:48 ` Xiaoyao Li
2024-03-07 12:52 ` Gupta, Pankaj
2024-03-12 2:59 ` Binbin Wu
2024-04-04 16:38 ` Sean Christopherson
2024-03-08 4:22 ` Yan Zhao
2024-04-04 16:45 ` Sean Christopherson
2024-02-28 2:41 ` [PATCH 02/16] KVM: x86: Remove separate "bit" defines for page fault error code masks Sean Christopherson
2024-02-29 12:44 ` Paolo Bonzini
2024-02-29 18:40 ` Sean Christopherson
2024-02-29 20:56 ` Paolo Bonzini
2024-02-29 13:43 ` Dongli Zhang
2024-02-29 15:25 ` Sean Christopherson
2024-02-28 2:41 ` [PATCH 03/16] KVM: x86: Define more SEV+ page fault error bits/flags for #NPF Sean Christopherson
2024-02-28 4:43 ` Dongli Zhang
2024-02-28 16:16 ` Sean Christopherson
2024-02-28 2:41 ` [PATCH 04/16] KVM: x86/mmu: Pass full 64-bit error code when handling page faults Sean Christopherson
2024-02-28 7:30 ` Dongli Zhang
2024-02-28 16:22 ` Sean Christopherson
2024-02-29 13:32 ` Dongli Zhang
2024-03-05 3:55 ` Xiaoyao Li
2024-02-28 2:41 ` [PATCH 05/16] KVM: x86/mmu: Use synthetic page fault error code to indicate private faults Sean Christopherson
2024-02-29 11:16 ` Huang, Kai
2024-02-29 15:17 ` Sean Christopherson
2024-03-06 9:43 ` Xu Yilun
2024-03-06 14:45 ` Sean Christopherson
2024-03-07 9:05 ` Xu Yilun
2024-03-07 14:36 ` Sean Christopherson
2024-03-12 5:34 ` Binbin Wu
2024-02-28 2:41 ` [PATCH 06/16] KVM: x86/mmu: WARN if upper 32 bits of legacy #PF error code are non-zero Sean Christopherson
2024-02-29 22:11 ` Huang, Kai
2024-02-29 23:07 ` Sean Christopherson
2024-03-12 5:44 ` Binbin Wu
2024-02-28 2:41 ` [PATCH 07/16] KVM: x86: Move synthetic PFERR_* sanity checks to SVM's #NPF handler Sean Christopherson
2024-02-29 22:19 ` Huang, Kai
2024-02-29 22:52 ` Sean Christopherson
2024-02-29 23:14 ` Huang, Kai
2024-03-12 9:44 ` Binbin Wu
2024-02-28 2:41 ` [PATCH 08/16] KVM: x86/mmu: WARN and skip MMIO cache on private, reserved page faults Sean Christopherson
2024-02-29 22:26 ` Huang, Kai
2024-02-29 23:06 ` Sean Christopherson
2024-02-29 23:21 ` Huang, Kai
2024-03-04 15:51 ` Sean Christopherson
2024-03-05 21:32 ` Huang, Kai
2024-03-06 0:25 ` Sean Christopherson
2024-02-28 2:41 ` [PATCH 09/16] KVM: x86/mmu: Move private vs. shared check above slot validity checks Sean Christopherson
2024-03-05 23:06 ` Huang, Kai
2024-03-06 0:38 ` Sean Christopherson
2024-03-06 1:22 ` Huang, Kai
2024-03-06 2:02 ` Sean Christopherson
2024-03-06 22:06 ` Huang, Kai
2024-03-06 23:49 ` Sean Christopherson
2024-03-07 0:28 ` Huang, Kai
2024-03-08 4:54 ` Xu Yilun
2024-03-08 23:28 ` Sean Christopherson
2024-03-11 4:43 ` Xu Yilun
2024-03-12 0:08 ` Sean Christopherson
2024-02-28 2:41 ` [PATCH 10/16] KVM: x86/mmu: Don't force emulation of L2 accesses to non-APIC internal slots Sean Christopherson
2024-03-07 0:03 ` Huang, Kai
2024-02-28 2:41 ` [PATCH 11/16] KVM: x86/mmu: Explicitly disallow private accesses to emulated MMIO Sean Christopherson
2024-03-06 22:35 ` Huang, Kai
2024-03-06 22:43 ` Sean Christopherson
2024-03-06 22:49 ` Huang, Kai
2024-03-06 23:01 ` Sean Christopherson
2024-03-06 23:20 ` Huang, Kai
2024-03-07 17:10 ` Kirill A. Shutemov
2024-03-08 0:09 ` Huang, Kai [this message]
2024-02-28 2:41 ` [PATCH 12/16] KVM: x86/mmu: Move slot checks from __kvm_faultin_pfn() to kvm_faultin_pfn() Sean Christopherson
2024-03-07 0:11 ` Huang, Kai
2024-02-28 2:41 ` [PATCH 13/16] KVM: x86/mmu: Handle no-slot faults at the beginning of kvm_faultin_pfn() Sean Christopherson
2024-03-07 0:48 ` Huang, Kai
2024-03-07 0:53 ` Sean Christopherson
2024-02-28 2:41 ` [PATCH 14/16] KVM: x86/mmu: Set kvm_page_fault.hva to KVM_HVA_ERR_BAD for "no slot" faults Sean Christopherson
2024-03-07 0:50 ` Huang, Kai
2024-03-07 1:01 ` Sean Christopherson
2024-02-28 2:41 ` [PATCH 15/16] KVM: x86/mmu: Initialize kvm_page_fault's pfn and hva to error values Sean Christopherson
2024-03-07 0:46 ` Huang, Kai
2024-02-28 2:41 ` [PATCH 16/16] KVM: x86/mmu: Sanity check that __kvm_faultin_pfn() doesn't create noslot pfns Sean Christopherson
2024-03-07 0:46 ` Huang, Kai
2024-04-17 12:48 ` [PATCH 00/16] KVM: x86/mmu: Page fault and MMIO cleanups Paolo Bonzini
2024-04-18 15:40 ` Sean Christopherson
2024-04-19 6:47 ` Xiaoyao Li
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