linux-kernel - Re: [RFC 04/16] KVM: selftests: set CPUID before setting sregs in vcpu creation

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Message-ID: <CAKiEG5rPhDgsVPcZV=DrjJNPk6qy9yVC1ZDdxo6VajnUgp3iRg@mail.gmail.com>
Date:   Fri, 8 Oct 2021 12:03:12 -0700
From:   Nathan Tempelman <natet@...gle.com>
To:     Michael Roth <michael.roth@....com>
Cc:     linux-kselftest@...r.kernel.org, kvm <kvm@...r.kernel.org>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Marc Orr <marcorr@...gle.com>,
        Steve Rutherford <srutherford@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Mingwei Zhang <mizhang@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Varad Gautam <varad.gautam@...e.com>,
        Shuah Khan <shuah@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Ricardo Koller <ricarkol@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>
Subject: Re: [RFC 04/16] KVM: selftests: set CPUID before setting sregs in
 vcpu creation

On Wed, Oct 6, 2021 at 1:39 PM Michael Roth <michael.roth@....com> wrote:
>
> Recent kernels have checks to ensure the GPA values in special-purpose
> registers like CR3 are within the maximum physical address range and
> don't overlap with anything in the upper/reserved range. In the case of
> SEV kselftest guests booting directly into 64-bit mode, CR3 needs to be
> initialized to the GPA of the page table root, with the encryption bit
> set. The kernel accounts for this encryption bit by removing it from
> reserved bit range when the guest advertises the bit position via
> KVM_SET_CPUID*, but kselftests currently call KVM_SET_SREGS as part of
> vm_vcpu_add_default(), *prior* to vCPU creation, so there's no
> opportunity to call KVM_SET_CPUID* in advance. As a result,
> KVM_SET_SREGS will return an error in these cases.
>
> Address this by moving vcpu_set_cpuid() (which calls KVM_SET_CPUID*)
> ahead of vcpu_setup() (which calls KVM_SET_SREGS).
>
> While there, address a typo in the assertion that triggers when
> KVM_SET_SREGS fails.
>
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Michael Roth <michael.roth@....com>
> ---
>  tools/testing/selftests/kvm/lib/kvm_util.c         | 2 +-
>  tools/testing/selftests/kvm/lib/x86_64/processor.c | 4 +---
>  2 files changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index ef88fdc7e46b..646cffd86d09 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -1906,7 +1906,7 @@ void vcpu_sregs_get(struct kvm_vm *vm, uint32_t vcpuid, struct kvm_sregs *sregs)
>  void vcpu_sregs_set(struct kvm_vm *vm, uint32_t vcpuid, struct kvm_sregs *sregs)
>  {
>         int ret = _vcpu_sregs_set(vm, vcpuid, sregs);
> -       TEST_ASSERT(ret == 0, "KVM_RUN IOCTL failed, "
> +       TEST_ASSERT(ret == 0, "KVM_SET_SREGS IOCTL failed, "
>                 "rc: %i errno: %i", ret, errno);
>  }
>
> diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> index 0bbd88fe1127..1ab4c20f5d12 100644
> --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> @@ -660,6 +660,7 @@ void vm_vcpu_add_default(struct kvm_vm *vm, uint32_t vcpuid, void *guest_code)
>
>         /* Create VCPU */
>         vm_vcpu_add(vm, vcpuid);
> +       vcpu_set_cpuid(vm, vcpuid, kvm_get_supported_cpuid());
>         vcpu_setup(vm, vcpuid);
>
>         /* Setup guest general purpose registers */
> @@ -672,9 +673,6 @@ void vm_vcpu_add_default(struct kvm_vm *vm, uint32_t vcpuid, void *guest_code)
>         /* Setup the MP state */
>         mp_state.mp_state = 0;
>         vcpu_set_mp_state(vm, vcpuid, &mp_state);
> -
> -       /* Setup supported CPUIDs */
> -       vcpu_set_cpuid(vm, vcpuid, kvm_get_supported_cpuid());
>  }
>
>  /*
> --
> 2.25.1
>

Good catch.
Reviewed-by: Nathan Tempelman <natet@...gle.com>