Re: [PATCH] allow enabling/disabling NPT by reloading only the architecture module

Avi Kivity
2008-07-15T10:56:10Z

Yang, Sheng wrote:
> On Tuesday 15 July 2008 02:36:36 Joerg Roedel wrote:
>
>> If NPT is enabled after loading both KVM modules on AMD and it
>> should be disabled, both KVM modules must be reloaded. If only the
>> architecture module is reloaded the behavior is undefined. With
>> this patch it is possible to disable NPT only by reloading the
>> kvm_amd module.
>>
>> Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
>> ---
>>
>
>
> From 3dd7fa4abb1cfc702b3fbd7038d585b541f981a4 Mon Sep 17 00:00:00 2001
> From: Sheng Yang <sheng.yang@intel.com>
> Date: Tue, 15 Jul 2008 14:18:29 +0800
> Subject: [PATCH] KVM: VMX: Fix undefined beaviour of EPT after reload
> kvm-intel.ko
>
> Based on Joerg Roedel's fix for NPT.
>
> Thanks Joerg!
>
> Signed-off-by: Sheng Yang <sheng.yang@intel.com>
> ---
> arch/x86/kvm/vmx.c | 15 +++++++++------
> 1 files changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 5f807e3..374e1ca 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3108,14 +3108,17 @@ static struct kvm_vcpu *vmx_create_vcpu(struct
> kvm *kvm, unsigned int id)
> return ERR_PTR(-ENOMEM);
>
> allocate_vpid(vmx);
> - if (id == 0 && vm_need_ept()) {
> - kvm_mmu_set_base_ptes(VMX_EPT_READABLE_MASK |
> - VMX_EPT_WRITABLE_MASK |
> - VMX_EPT_DEFAULT_MT << VMX_EPT_MT_EPTE_SHIFT);
> - kvm_mmu_set_mask_ptes(0ull, VMX_EPT_FAKE_ACCESSED_MASK,
> + if (id == 0) {
> + if (vm_need_ept()) {
> + kvm_mmu_set_base_ptes(VMX_EPT_READABLE_MASK |
> + VMX_EPT_WRITABLE_MASK |
> + VMX_EPT_DEFAULT_MT << VMX_EPT_MT_EPTE_SHIFT);
> + kvm_mmu_set_mask_ptes(0ull, VMX_EPT_FAKE_ACCESSED_MASK,
> VMX_EPT_FAKE_DIRTY_MASK, 0ull,
> VMX_EPT_EXECUTABLE_MASK);
> - kvm_enable_tdp();
> + kvm_enable_tdp();
> + } else
> + kvm_disable_tdp();
> }
>
>
>

hmm, what is this code doing in vmx_create_vcpu()? surely vmx_init() is
a better place?

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.