From: Xiaoyao Li <xiaoyao.li@intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Kai Huang <kai.huang@intel.com>,
Binbin Wu <binbin.wu@linux.intel.com>
Subject: Re: [PATCH 04/17] KVM: x86: Move synthetic PFERR_* sanity checks to SVM's #NPF handler
Date: Tue, 14 May 2024 12:25:51 +0800 [thread overview]
Message-ID: <55d00dc8-bfa3-4cf2-9c6a-1d81e5cfd7b3@intel.com> (raw)
In-Reply-To: <ZkJOb4zJJnOAYnTi@google.com>
On 5/14/2024 1:31 AM, Sean Christopherson wrote:
> On Mon, May 13, 2024, Xiaoyao Li wrote:
>> On 5/7/2024 11:58 PM, Paolo Bonzini wrote:
>>> From: Sean Christopherson <seanjc@google.com>
>>>
>>> Move the sanity check that hardware never sets bits that collide with KVM-
>>> define synthetic bits from kvm_mmu_page_fault() to npf_interception(),
>>> i.e. make the sanity check #NPF specific. The legacy #PF path already
>>> WARNs if _any_ of bits 63:32 are set, and the error code that comes from
>>> VMX's EPT Violatation and Misconfig is 100% synthesized (KVM morphs VMX's
>>> EXIT_QUALIFICATION into error code flags).
>>>
>>> Add a compile-time assert in the legacy #PF handler to make sure that KVM-
>>> define flags are covered by its existing sanity check on the upper bits.
>>>
>>> Opportunistically add a description of PFERR_IMPLICIT_ACCESS, since we
>>> are removing the comment that defined it.
>>>
>>> Signed-off-by: Sean Christopherson <seanjc@google.com>
>>> Reviewed-by: Kai Huang <kai.huang@intel.com>
>>> Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
>>> Message-ID: <20240228024147.41573-8-seanjc@google.com>
>>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>> ---
>>> arch/x86/include/asm/kvm_host.h | 6 ++++++
>>> arch/x86/kvm/mmu/mmu.c | 14 +++-----------
>>> arch/x86/kvm/svm/svm.c | 9 +++++++++
>>> 3 files changed, 18 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>>> index 58bbcf76ad1e..12e727301262 100644
>>> --- a/arch/x86/include/asm/kvm_host.h
>>> +++ b/arch/x86/include/asm/kvm_host.h
>>> @@ -267,7 +267,13 @@ enum x86_intercept_stage;
>>> #define PFERR_GUEST_ENC_MASK BIT_ULL(34)
>>> #define PFERR_GUEST_SIZEM_MASK BIT_ULL(35)
>>> #define PFERR_GUEST_VMPL_MASK BIT_ULL(36)
>>> +
>>> +/*
>>> + * IMPLICIT_ACCESS is a KVM-defined flag used to correctly perform SMAP checks
>>> + * when emulating instructions that triggers implicit access.
>>> + */
>>> #define PFERR_IMPLICIT_ACCESS BIT_ULL(48)
>>> +#define PFERR_SYNTHETIC_MASK (PFERR_IMPLICIT_ACCESS)
>>> #define PFERR_NESTED_GUEST_PAGE (PFERR_GUEST_PAGE_MASK | \
>>> PFERR_WRITE_MASK | \
>>> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
>>> index c72a2033ca96..5562d693880a 100644
>>> --- a/arch/x86/kvm/mmu/mmu.c
>>> +++ b/arch/x86/kvm/mmu/mmu.c
>>> @@ -4502,6 +4502,9 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
>>> return -EFAULT;
>>> #endif
>>> + /* Ensure the above sanity check also covers KVM-defined flags. */
>>
>> 1. There is no sanity check above related to KVM-defined flags yet. It has
>> to be after Patch 6.
>
> Ya, it's not just the comment, the entire changelog expects this patch to land
> after patch 6.
>>
>> 2. I somehow cannot parse the comment properly, though I know it's to ensure
>> KVM-defined PFERR_SYNTHETIC_MASK not contain any bit below 32-bits.
>
> Hmm, how about this?
>
> /*
> * Ensure that the above sanity check on hardware error code bits 63:32
> * also prevents false positives on KVM-defined flags.
> */
>
Maybe it's just myself inability, I still cannot interpret it well.
Can't we put it above the sanity check of error code, and just with a
comment like
/*
* Ensure KVM-defined flags not occupied any bits below 32-bits,
* that are used by hardware.
* /
next prev parent reply other threads:[~2024-05-14 4:25 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 15:58 [PATCH v2 00/17] KVM: x86/mmu: Page fault and MMIO cleanups Paolo Bonzini
2024-05-07 15:58 ` [PATCH 01/17] KVM: x86/mmu: Exit to userspace with -EFAULT if private fault hits emulation Paolo Bonzini
2024-05-13 5:25 ` Xiaoyao Li
2024-05-07 15:58 ` [PATCH 02/17] KVM: x86: Remove separate "bit" defines for page fault error code masks Paolo Bonzini
2024-05-13 5:29 ` Xiaoyao Li
2024-05-07 15:58 ` [PATCH 03/17] KVM: x86: Define more SEV+ page fault error bits/flags for #NPF Paolo Bonzini
2024-05-07 15:58 ` [PATCH 04/17] KVM: x86: Move synthetic PFERR_* sanity checks to SVM's #NPF handler Paolo Bonzini
2024-05-13 5:50 ` Xiaoyao Li
2024-05-13 17:31 ` Sean Christopherson
2024-05-14 4:25 ` Xiaoyao Li [this message]
2024-05-14 15:32 ` Sean Christopherson
2024-05-15 1:03 ` Xiaoyao Li
2024-05-07 15:58 ` [PATCH 05/17] KVM: x86/mmu: Pass full 64-bit error code when handling page faults Paolo Bonzini
2024-05-07 15:58 ` [PATCH 06/17] KVM: x86/mmu: WARN if upper 32 bits of legacy #PF error code are non-zero Paolo Bonzini
2024-05-07 15:58 ` [PATCH 07/17] KVM: x86/mmu: Use synthetic page fault error code to indicate private faults Paolo Bonzini
2024-05-13 5:56 ` Xiaoyao Li
2024-05-07 15:58 ` [PATCH 08/17] KVM: x86/mmu: check for invalid async page faults involving private memory Paolo Bonzini
2024-05-07 15:58 ` [PATCH 09/17] KVM: x86/mmu: WARN and skip MMIO cache on private, reserved page faults Paolo Bonzini
2024-05-13 6:15 ` Xiaoyao Li
2024-05-07 15:58 ` [PATCH 10/17] KVM: x86/mmu: Move private vs. shared check above slot validity checks Paolo Bonzini
2024-05-13 6:22 ` Xiaoyao Li
2024-05-07 15:58 ` [PATCH 11/17] KVM: x86/mmu: Don't force emulation of L2 accesses to non-APIC internal slots Paolo Bonzini
2024-05-07 15:58 ` [PATCH 12/17] KVM: x86/mmu: Explicitly disallow private accesses to emulated MMIO Paolo Bonzini
2024-05-13 6:26 ` Xiaoyao Li
2024-05-07 15:58 ` [PATCH 13/17] KVM: x86/mmu: Move slot checks from __kvm_faultin_pfn() to kvm_faultin_pfn() Paolo Bonzini
2024-05-13 6:27 ` Xiaoyao Li
2024-05-07 15:58 ` [PATCH 14/17] KVM: x86/mmu: Handle no-slot faults at the beginning of kvm_faultin_pfn() Paolo Bonzini
2024-05-13 6:28 ` Xiaoyao Li
2024-05-07 15:58 ` [PATCH 15/17] KVM: x86/mmu: Set kvm_page_fault.hva to KVM_HVA_ERR_BAD for "no slot" faults Paolo Bonzini
2024-05-13 6:28 ` Xiaoyao Li
2024-05-07 15:58 ` [PATCH 16/17] KVM: x86/mmu: Initialize kvm_page_fault's pfn and hva to error values Paolo Bonzini
2024-05-13 6:29 ` Xiaoyao Li
2024-05-07 15:58 ` [PATCH 17/17] KVM: x86/mmu: Sanity check that __kvm_faultin_pfn() doesn't create noslot pfns Paolo Bonzini
2024-05-13 6:40 ` Xiaoyao Li
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