From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH] KVM: x86: Mark CR4.UMIP as reserved based on associated CPUID bit
Date: Wed, 29 Jan 2020 16:08:29 +0100 [thread overview]
Message-ID: <87a7669u6q.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20200128235344.29581-1-sean.j.christopherson@intel.com>
Sean Christopherson <sean.j.christopherson@intel.com> writes:
> Re-add code to mark CR4.UMIP as reserved if UMIP is not supported by the
> host. The UMIP handling was unintentionally dropped during a recent
> refactoring.
>
> Not flagging CR4.UMIP allows the guest to set its CR4.UMIP regardless of
> host support or userspace desires. On CPUs with UMIP support, including
> emulated UMIP, this allows the guest to enable UMIP against the wishes
> of the userspace VMM. On CPUs without any form of UMIP, this results in
> a failed VM-Enter due to invalid guest state.
>
> Fixes: 345599f9a2928 ("KVM: x86: Add macro to ensure reserved cr4 bits checks stay in sync")
This one in only in kvm/next so just in case another force-push is
around the corner I'd suggest we squash this change in :-)
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/kvm/x86.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 7e3f1d937224..e70d1215638a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -898,6 +898,8 @@ EXPORT_SYMBOL_GPL(kvm_set_xcr);
> __reserved_bits |= X86_CR4_PKE; \
> if (!__cpu_has(__c, X86_FEATURE_LA57)) \
> __reserved_bits |= X86_CR4_LA57; \
> + if (!__cpu_has(__c, X86_FEATURE_UMIP)) \
> + __reserved_bits |= X86_CR4_UMIP; \
> __reserved_bits; \
> })
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
--
Vitaly
next prev parent reply other threads:[~2020-01-29 15:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-28 23:53 [PATCH] KVM: x86: Mark CR4.UMIP as reserved based on associated CPUID bit Sean Christopherson
2020-01-29 15:08 ` Vitaly Kuznetsov [this message]
2020-02-05 15:30 ` Paolo Bonzini
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