Re: [PATCH v3 8/9] x86/kvm/mmu: check if tdp/shadow MMU reconfiguration is needed

Sean Christopherson
2018-10-05T19:37:07Z

On Mon, Oct 01, 2018 at 04:20:09PM +0200, Vitaly Kuznetsov wrote:
> MMU reconfiguration in init_kvm_tdp_mmu()/kvm_init_shadow_mmu() can be
> avoided if the source data used to configure it didn't change; enhance
> MMU extended role with the required fields and consolidate common code in
> kvm_calc_mmu_role_common().
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>

Same comments about kvm_read_cr4_bits(), otherwise:

Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>

> ---
> Changes since v2:
> - Rename 'mmu_init' parameter to 'base_only' [Sean Christopherson]
> ---
> arch/x86/include/asm/kvm_host.h | 2 +
> arch/x86/kvm/mmu.c | 95 +++++++++++++++++++++------------
> 2 files changed, 63 insertions(+), 34 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 87ddaa1579e7..609811066580 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -284,10 +284,12 @@ union kvm_mmu_extended_role {
> struct {
> unsigned int valid:1;
> unsigned int execonly:1;
> + unsigned int cr0_pg:1;
> unsigned int cr4_pse:1;
> unsigned int cr4_pke:1;
> unsigned int cr4_smap:1;
> unsigned int cr4_smep:1;
> + unsigned int cr4_la57:1;
> };
> };
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index d303f722d671..10b39ff83943 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -4712,27 +4712,46 @@ static union kvm_mmu_extended_role kvm_calc_mmu_role_ext(struct kvm_vcpu *vcpu)
> {
> union kvm_mmu_extended_role ext = {0};
>
> + ext.cr0_pg = !!is_paging(vcpu);
> ext.cr4_smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP) != 0;
> ext.cr4_smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP) != 0;
> ext.cr4_pse = !!is_pse(vcpu);
> ext.cr4_pke = kvm_read_cr4_bits(vcpu, X86_CR4_PKE) != 0;
> + ext.cr4_la57 = kvm_read_cr4_bits(vcpu, X86_CR4_LA57) != 0;

Can be !!kvm_read_cr4_bits() or maybe just kvm_read_cr4_bits().

>
> ext.valid = 1;
>
> return ext;
> }
>
> -static union kvm_mmu_page_role
> -kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu)
> +static union kvm_mmu_role kvm_calc_mmu_role_common(struct kvm_vcpu *vcpu,
> + bool base_only)
> +{
> + union kvm_mmu_role role = {0};
> +
> + role.base.access = ACC_ALL;
> + role.base.nxe = !!is_nx(vcpu);
> + role.base.cr4_pae = !!is_pae(vcpu);
> + role.base.cr0_wp = is_write_protection(vcpu);
> + role.base.smm = is_smm(vcpu);
> + role.base.guest_mode = is_guest_mode(vcpu);
> +
> + if (base_only)
> + return role;
> +
> + role.ext = kvm_calc_mmu_role_ext(vcpu);
> +
> + return role;
> +}
> +
> +static union kvm_mmu_role
> +kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu, bool base_only)
> {
> - union kvm_mmu_page_role role = {0};
> + union kvm_mmu_role role = kvm_calc_mmu_role_common(vcpu, base_only);
>
> - role.guest_mode = is_guest_mode(vcpu);
> - role.smm = is_smm(vcpu);
> - role.ad_disabled = (shadow_accessed_mask == 0);
> - role.level = kvm_x86_ops->get_tdp_level(vcpu);
> - role.direct = true;
> - role.access = ACC_ALL;
> + role.base.ad_disabled = (shadow_accessed_mask == 0);
> + role.base.level = kvm_x86_ops->get_tdp_level(vcpu);
> + role.base.direct = true;
>
> return role;
> }
> @@ -4740,9 +4759,14 @@ kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu)
> static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
> {
> struct kvm_mmu *context = vcpu->arch.mmu;
> + union kvm_mmu_role new_role =
> + kvm_calc_tdp_mmu_root_page_role(vcpu, false);
>
> - context->mmu_role.base.word = mmu_base_role_mask.word &
> - kvm_calc_tdp_mmu_root_page_role(vcpu).word;
> + new_role.base.word &= mmu_base_role_mask.word;
> + if (new_role.as_u64 == context->mmu_role.as_u64)
> + return;
> +
> + context->mmu_role.as_u64 = new_role.as_u64;
> context->page_fault = tdp_page_fault;
> context->sync_page = nonpaging_sync_page;
> context->invlpg = nonpaging_invlpg;
> @@ -4782,29 +4806,23 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
> reset_tdp_shadow_zero_bits_mask(vcpu, context);
> }
>
> -static union kvm_mmu_page_role
> -kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu)
> -{
> - union kvm_mmu_page_role role = {0};
> - bool smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP);
> - bool smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP);
> -
> - role.nxe = is_nx(vcpu);
> - role.cr4_pae = !!is_pae(vcpu);
> - role.cr0_wp = is_write_protection(vcpu);
> - role.smep_andnot_wp = smep && !is_write_protection(vcpu);
> - role.smap_andnot_wp = smap && !is_write_protection(vcpu);
> - role.guest_mode = is_guest_mode(vcpu);
> - role.smm = is_smm(vcpu);
> - role.direct = !is_paging(vcpu);
> - role.access = ACC_ALL;
> +static union kvm_mmu_role
> +kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu, bool base_only)
> +{
> + union kvm_mmu_role role = kvm_calc_mmu_role_common(vcpu, base_only);
> +
> + role.base.smep_andnot_wp = role.ext.cr4_smep &&
> + !is_write_protection(vcpu);
> + role.base.smap_andnot_wp = role.ext.cr4_smap &&
> + !is_write_protection(vcpu);
> + role.base.direct = !is_paging(vcpu);
>
> if (!is_long_mode(vcpu))
> - role.level = PT32E_ROOT_LEVEL;
> + role.base.level = PT32E_ROOT_LEVEL;
> else if (is_la57_mode(vcpu))
> - role.level = PT64_ROOT_5LEVEL;
> + role.base.level = PT64_ROOT_5LEVEL;
> else
> - role.level = PT64_ROOT_4LEVEL;
> + role.base.level = PT64_ROOT_4LEVEL;
>
> return role;
> }
> @@ -4812,6 +4830,12 @@ kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu)
> void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu)
> {
> struct kvm_mmu *context = vcpu->arch.mmu;
> + union kvm_mmu_role new_role =
> + kvm_calc_shadow_mmu_root_page_role(vcpu, false);
> +
> + new_role.base.word &= mmu_base_role_mask.word;
> + if (new_role.as_u64 == context->mmu_role.as_u64)
> + return;
>
> if (!is_paging(vcpu))
> nonpaging_init_context(vcpu, context);
> @@ -4822,8 +4846,7 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu)
> else
> paging32_init_context(vcpu, context);
>
> - context->mmu_role.base.word = mmu_base_role_mask.word &
> - kvm_calc_shadow_mmu_root_page_role(vcpu).word;
> + context->mmu_role.as_u64 = new_role.as_u64;
> reset_shadow_zero_bits_mask(vcpu, context);
> }
> EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu);
> @@ -4961,10 +4984,14 @@ EXPORT_SYMBOL_GPL(kvm_init_mmu);
> static union kvm_mmu_page_role
> kvm_mmu_calc_root_page_role(struct kvm_vcpu *vcpu)
> {
> + union kvm_mmu_role role;
> +
> if (tdp_enabled)
> - return kvm_calc_tdp_mmu_root_page_role(vcpu);
> + role = kvm_calc_tdp_mmu_root_page_role(vcpu, true);
> else
> - return kvm_calc_shadow_mmu_root_page_role(vcpu);
> + role = kvm_calc_shadow_mmu_root_page_role(vcpu, true);
> +
> + return role.base;
> }
>
> void kvm_mmu_reset_context(struct kvm_vcpu *vcpu)
> --
> 2.17.1
>