From: Paolo Bonzini <pbonzini@redhat.com>
To: Jim Mattson <jmattson@google.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
Mohammed Gamal <mgamal@redhat.com>,
kvm list <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH v3 7/9] KVM: VMX: Add guest physical address check in EPT violation and misconfig
Date: Fri, 23 Oct 2020 19:16:41 +0200 [thread overview]
Message-ID: <f40e5d23-88b6-01c0-60f9-5419dac703a2@redhat.com> (raw)
In-Reply-To: <CALMp9eQ8C0pp5yP4tLsckVWq=j3Xb=e4M7UVZz67+pngaXJJUw@mail.gmail.com>
On 23/10/20 18:59, Jim Mattson wrote:
>> The problem is that page fault error code bits cannot be reconstructed
>> from bits 0..2 of the EPT violation exit qualification, if bit 8 is
>> clear in the exit qualification (that is, if the access causing the EPT
>> violation is to a paging-structure entry). In that case bits 0..2 refer
>> to the paging-structure access rather than to the final access. In fact
>> advanced information is not available at all for paging-structure access
>> EPT violations.
>
> True, but the in-kernel emulator can only handle a very small subset
> of the available instructions.
>
> If bit 8 is set in the exit qualification, we should use the advanced
> VM-exit information. If it's clear, we should just do a software page
> walk of the guest's x86 page tables.
The information that we need is _not_ that provided by the advanced
VM-exit information (or by a page walk). If a page is neither writable
nor executable, the advanced information doesn't say if the injected #PF
should be a W=1 or a F=1 fault. We need the information in bits 0..2 of
the exit qualification for the final access, which however is not
available for the paging-structure access.
If bit 8 is set, however, we need not use the emulator indeed, as the
W/F/U bits are all available from either the exit qualification or in
the SS access rights. The access.flat test in kvm-unit-tests covers all
this, so it will be easy to check the theory.
Paolo
> The in-kernel emulator should
> only be used as a last resort on hardware that doesn't support the
> advanced VM-exit information for EPT violations.
>
next prev parent reply other threads:[~2020-10-23 17:16 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-10 15:48 [PATCH v3 0/9] KVM: Support guest MAXPHYADDR < host MAXPHYADDR Mohammed Gamal
2020-07-10 15:48 ` [PATCH v3 1/9] KVM: x86: Add helper functions for illegal GPA checking and page fault injection Mohammed Gamal
2020-07-10 15:48 ` [PATCH v3 2/9] KVM: x86: mmu: Move translate_gpa() to mmu.c Mohammed Gamal
2020-07-10 15:48 ` [PATCH v3 3/9] KVM: x86: mmu: Add guest physical address check in translate_gpa() Mohammed Gamal
2020-07-10 17:41 ` Paolo Bonzini
2020-07-10 15:48 ` [PATCH v3 4/9] KVM: x86: rename update_bp_intercept to update_exception_bitmap Mohammed Gamal
2020-07-10 16:15 ` Jim Mattson
2020-07-10 15:48 ` [PATCH v3 5/9] KVM: x86: update exception bitmap on CPUID changes Mohammed Gamal
2020-07-10 16:25 ` Jim Mattson
2020-07-10 15:48 ` [PATCH v3 6/9] KVM: VMX: introduce vmx_need_pf_intercept Mohammed Gamal
2020-07-10 15:48 ` [PATCH v3 7/9] KVM: VMX: Add guest physical address check in EPT violation and misconfig Mohammed Gamal
2020-07-13 18:32 ` Sean Christopherson
2020-07-15 23:00 ` Sean Christopherson
2020-08-17 17:22 ` Sean Christopherson
2020-08-17 18:01 ` Paolo Bonzini
2020-10-09 16:17 ` Jim Mattson
2020-10-14 23:44 ` Jim Mattson
2020-10-23 3:14 ` Sean Christopherson
2020-10-23 9:22 ` Paolo Bonzini
2020-10-23 16:59 ` Jim Mattson
2020-10-23 17:16 ` Paolo Bonzini [this message]
2020-10-23 17:23 ` Jim Mattson
2020-10-23 17:43 ` Paolo Bonzini
2021-01-15 19:35 ` Jim Mattson
2021-01-20 21:16 ` Jim Mattson
2021-01-27 20:57 ` Jim Mattson
2021-06-21 18:31 ` Jim Mattson
2020-07-10 15:48 ` [PATCH v3 8/9] KVM: VMX: optimize #PF injection when MAXPHYADDR does not match Mohammed Gamal
2020-07-10 15:48 ` [PATCH v3 9/9] KVM: x86: SVM: VMX: Make GUEST_MAXPHYADDR < HOST_MAXPHYADDR support configurable Mohammed Gamal
2020-07-10 17:40 ` Paolo Bonzini
2020-07-10 16:30 ` [PATCH v3 0/9] KVM: Support guest MAXPHYADDR < host MAXPHYADDR Jim Mattson
2020-07-10 17:06 ` Paolo Bonzini
2020-07-10 17:13 ` Jim Mattson
2020-07-10 17:16 ` Paolo Bonzini
2020-07-10 17:26 ` Sean Christopherson
2020-07-10 17:26 ` Jim Mattson
2020-07-10 17:40 ` Paolo Bonzini
2020-07-10 17:49 ` Paolo Bonzini
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