From: "Huang, Kai" <kai.huang@intel.com>
To: "pbonzini@redhat.com" <pbonzini@redhat.com>,
"seanjc@google.com" <seanjc@google.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/3] KVM: x86: Explicitly zero kvm_caps during vendor module load
Date: Wed, 24 Apr 2024 03:25:45 +0000 [thread overview]
Message-ID: <8e3ad8fa55a26d8726ef0b68e40f59cbcdac1f6c.camel@intel.com> (raw)
In-Reply-To: <20240423165328.2853870-4-seanjc@google.com>
On Tue, 2024-04-23 at 09:53 -0700, Sean Christopherson wrote:
> Zero out all of kvm_caps when loading a new vendor module to ensure that
> KVM can't inadvertently rely on global initialization of a field, and add
> a comment above the definition of kvm_caps to call out that all fields
> needs to be explicitly computed during vendor module load.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/x86.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 44ce187bad89..8f3979d5fc80 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -92,6 +92,11 @@
> #define MAX_IO_MSRS 256
> #define KVM_MAX_MCE_BANKS 32
>
> +/*
> + * Note, kvm_caps fields should *never* have default values, all fields must be
> + * recomputed from scratch during vendor module load, e.g. to account for a
> + * vendor module being reloaded with different module parameters.
> + */
> struct kvm_caps kvm_caps __read_mostly;
> EXPORT_SYMBOL_GPL(kvm_caps);
>
> @@ -9755,6 +9760,8 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
> return -EIO;
> }
>
> + memset(&kvm_caps, 0, sizeof(kvm_caps));
> +
> x86_emulator_cache = kvm_alloc_emulator_cache();
> if (!x86_emulator_cache) {
> pr_err("failed to allocate cache for x86 emulator\n");
Why do the memset() here particularly?
Isn't it better to put ...
memset(&kvm_caps, 0, sizeof(kvm_caps));
kvm_caps.supported_vm_types = BIT(KVM_X86_DEFAULT_VM);
kvm_caps.supported_mce_cap = MCG_CTL_P | MCG_SER_P;
... together so it can be easily seen?
We can even have a helper to do above to "reset kvm_caps to default
values" I think.
next prev parent reply other threads:[~2024-04-24 3:25 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-23 16:53 [PATCH 0/3] KVM: x86: Fix supported VM_TYPES caps Sean Christopherson
2024-04-23 16:53 ` [PATCH 1/3] KVM: x86: Fully re-initialize supported_vm_types on vendor module load Sean Christopherson
2024-04-23 16:53 ` [PATCH 2/3] KVM: x86: Fully re-initialize supported_mce_cap " Sean Christopherson
2024-04-23 16:53 ` [PATCH 3/3] KVM: x86: Explicitly zero kvm_caps during " Sean Christopherson
2024-04-24 3:25 ` Huang, Kai [this message]
2024-04-24 15:33 ` Sean Christopherson
2024-04-25 10:07 ` Huang, Kai
2024-04-25 13:43 ` [PATCH 0/3] KVM: x86: Fix supported VM_TYPES caps Xiaoyao Li
2024-04-25 14:30 ` Sean Christopherson
2024-04-26 1:17 ` Huang, Kai
2024-04-26 15:47 ` Sean Christopherson
2024-04-29 2:45 ` Huang, Kai
2024-04-29 15:56 ` Sean Christopherson
2024-05-07 17:20 ` Paolo Bonzini
2024-05-07 17:08 ` Paolo Bonzini
2024-05-10 14:50 ` Paolo Bonzini
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