From: Sean Christopherson <seanjc@google.com>
To: Xiaoyao Li <xiaoyao.li@intel.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: Mon, 13 May 2024 10:31:27 -0700 [thread overview]
Message-ID: <ZkJOb4zJJnOAYnTi@google.com> (raw)
In-Reply-To: <3b6bc6ac-276f-4a83-8972-68b98db672c7@intel.com>
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.
*/
next prev parent reply other threads:[~2024-05-13 17:31 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 [this message]
2024-05-14 4:25 ` Xiaoyao Li
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ZkJOb4zJJnOAYnTi@google.com \
--to=seanjc@google.com \
--cc=binbin.wu@linux.intel.com \
--cc=kai.huang@intel.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=xiaoyao.li@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).