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Date: Mon, 4 May 2020 18:52:07 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <sean.j.christopherson@...el.com>
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86/mmu: Add a helper to consolidate root sp
allocation
On 28/04/20 04:37, Sean Christopherson wrote:
> Add a helper, mmu_alloc_root(), to consolidate the allocation of a root
> shadow page, which has the same basic mechanics for all flavors of TDP
> and shadow paging.
>
> Note, __pa(sp->spt) doesn't need to be protected by mmu_lock, sp->spt
> points at a kernel page.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
> arch/x86/kvm/mmu/mmu.c | 88 +++++++++++++++++++-----------------------
> 1 file changed, 39 insertions(+), 49 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index e618472c572b..80205aea296e 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3685,37 +3685,43 @@ static int mmu_check_root(struct kvm_vcpu *vcpu, gfn_t root_gfn)
> return ret;
> }
>
> +static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, gva_t gva,
> + u8 level, bool direct)
> +{
> + struct kvm_mmu_page *sp;
> +
> + spin_lock(&vcpu->kvm->mmu_lock);
> +
> + if (make_mmu_pages_available(vcpu)) {
> + spin_unlock(&vcpu->kvm->mmu_lock);
> + return INVALID_PAGE;
> + }
> + sp = kvm_mmu_get_page(vcpu, gfn, gva, level, direct, ACC_ALL);
> + ++sp->root_count;
> +
> + spin_unlock(&vcpu->kvm->mmu_lock);
> + return __pa(sp->spt);
> +}
> +
> static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
> {
> - struct kvm_mmu_page *sp;
> + u8 shadow_root_level = vcpu->arch.mmu->shadow_root_level;
> + hpa_t root;
> unsigned i;
>
> - if (vcpu->arch.mmu->shadow_root_level >= PT64_ROOT_4LEVEL) {
> - spin_lock(&vcpu->kvm->mmu_lock);
> - if(make_mmu_pages_available(vcpu) < 0) {
> - spin_unlock(&vcpu->kvm->mmu_lock);
> + if (shadow_root_level >= PT64_ROOT_4LEVEL) {
> + root = mmu_alloc_root(vcpu, 0, 0, shadow_root_level, true);
> + if (!VALID_PAGE(root))
> return -ENOSPC;
> - }
> - sp = kvm_mmu_get_page(vcpu, 0, 0,
> - vcpu->arch.mmu->shadow_root_level, 1, ACC_ALL);
> - ++sp->root_count;
> - spin_unlock(&vcpu->kvm->mmu_lock);
> - vcpu->arch.mmu->root_hpa = __pa(sp->spt);
> - } else if (vcpu->arch.mmu->shadow_root_level == PT32E_ROOT_LEVEL) {
> + vcpu->arch.mmu->root_hpa = root;
> + } else if (shadow_root_level == PT32E_ROOT_LEVEL) {
> for (i = 0; i < 4; ++i) {
> - hpa_t root = vcpu->arch.mmu->pae_root[i];
> + MMU_WARN_ON(VALID_PAGE(vcpu->arch.mmu->pae_root[i]));
>
> - MMU_WARN_ON(VALID_PAGE(root));
> - spin_lock(&vcpu->kvm->mmu_lock);
> - if (make_mmu_pages_available(vcpu) < 0) {
> - spin_unlock(&vcpu->kvm->mmu_lock);
> + root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT),
> + i << 30, PT32_ROOT_LEVEL, true);
> + if (!VALID_PAGE(root))
> return -ENOSPC;
> - }
> - sp = kvm_mmu_get_page(vcpu, i << (30 - PAGE_SHIFT),
> - i << 30, PT32_ROOT_LEVEL, 1, ACC_ALL);
> - root = __pa(sp->spt);
> - ++sp->root_count;
> - spin_unlock(&vcpu->kvm->mmu_lock);
> vcpu->arch.mmu->pae_root[i] = root | PT_PRESENT_MASK;
> }
> vcpu->arch.mmu->root_hpa = __pa(vcpu->arch.mmu->pae_root);
> @@ -3730,9 +3736,9 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
>
> static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
> {
> - struct kvm_mmu_page *sp;
> u64 pdptr, pm_mask;
> gfn_t root_gfn, root_pgd;
> + hpa_t root;
> int i;
>
> root_pgd = vcpu->arch.mmu->get_guest_pgd(vcpu);
> @@ -3746,20 +3752,12 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
> * write-protect the guests page table root.
> */
> if (vcpu->arch.mmu->root_level >= PT64_ROOT_4LEVEL) {
> - hpa_t root = vcpu->arch.mmu->root_hpa;
> + MMU_WARN_ON(VALID_PAGE(vcpu->arch.mmu->root_hpa));
>
> - MMU_WARN_ON(VALID_PAGE(root));
> -
> - spin_lock(&vcpu->kvm->mmu_lock);
> - if (make_mmu_pages_available(vcpu) < 0) {
> - spin_unlock(&vcpu->kvm->mmu_lock);
> + root = mmu_alloc_root(vcpu, root_gfn, 0,
> + vcpu->arch.mmu->shadow_root_level, false);
> + if (!VALID_PAGE(root))
> return -ENOSPC;
> - }
> - sp = kvm_mmu_get_page(vcpu, root_gfn, 0,
> - vcpu->arch.mmu->shadow_root_level, 0, ACC_ALL);
> - root = __pa(sp->spt);
> - ++sp->root_count;
> - spin_unlock(&vcpu->kvm->mmu_lock);
> vcpu->arch.mmu->root_hpa = root;
> goto set_root_pgd;
> }
> @@ -3774,9 +3772,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
> pm_mask |= PT_ACCESSED_MASK | PT_WRITABLE_MASK | PT_USER_MASK;
>
> for (i = 0; i < 4; ++i) {
> - hpa_t root = vcpu->arch.mmu->pae_root[i];
> -
> - MMU_WARN_ON(VALID_PAGE(root));
> + MMU_WARN_ON(VALID_PAGE(vcpu->arch.mmu->pae_root[i]));
> if (vcpu->arch.mmu->root_level == PT32E_ROOT_LEVEL) {
> pdptr = vcpu->arch.mmu->get_pdptr(vcpu, i);
> if (!(pdptr & PT_PRESENT_MASK)) {
> @@ -3787,17 +3783,11 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
> if (mmu_check_root(vcpu, root_gfn))
> return 1;
> }
> - spin_lock(&vcpu->kvm->mmu_lock);
> - if (make_mmu_pages_available(vcpu) < 0) {
> - spin_unlock(&vcpu->kvm->mmu_lock);
> - return -ENOSPC;
> - }
> - sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30, PT32_ROOT_LEVEL,
> - 0, ACC_ALL);
> - root = __pa(sp->spt);
> - ++sp->root_count;
> - spin_unlock(&vcpu->kvm->mmu_lock);
>
> + root = mmu_alloc_root(vcpu, root_gfn, i << 30,
> + PT32_ROOT_LEVEL, false);
> + if (!VALID_PAGE(root))
> + return -ENOSPC;
> vcpu->arch.mmu->pae_root[i] = root | pm_mask;
> }
> vcpu->arch.mmu->root_hpa = __pa(vcpu->arch.mmu->pae_root);
>
Queued, thanks.
Paolo
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