kvm.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Kai Huang <kai.huang@intel.com>
To: kvm@vger.kernel.org
Cc: pbonzini@redhat.com, bgardon@google.com, seanjc@google.com,
	vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com,
	joro@8bytes.org
Subject: Re: [PATCH v2 3/3] KVM: x86/mmu: Fix TDP MMU page table level
Date: Fri, 07 May 2021 11:46:52 +1200	[thread overview]
Message-ID: <6e9c2f0b6e36342ee4955178a92fa34c47c6de99.camel@intel.com> (raw)
In-Reply-To: <d689dc6f19fc92d3db64065377df2eb48c09f07b.1620343751.git.kai.huang@intel.com>

Oops, this patch has a merge conflict with latest kvm/queue due to patch 
ff76d506030da ("KVM: x86/mmu: Avoid unnecessary page table allocation in
kvm_tdp_mmu_map()), but it is very easy to resolve.

Sorry that I forgot to git pull before sending those :)

On Fri, 2021-05-07 at 11:34 +1200, Kai Huang wrote:
> TDP MMU iterator's level is identical to page table's actual level.  For
> instance, for the last level page table (whose entry points to one 4K
> page), iter->level is 1 (PG_LEVEL_4K), and in case of 5 level paging,
> the iter->level is mmu->shadow_root_level, which is 5.  However, struct
> kvm_mmu_page's level currently is not set correctly when it is allocated
> in kvm_tdp_mmu_map().  When iterator hits non-present SPTE and needs to
> allocate a new child page table, currently iter->level, which is the
> level of the page table where the non-present SPTE belongs to, is used.
> This results in struct kvm_mmu_page's level always having its parent's
> level (excpet root table's level, which is initialized explicitly using
> mmu->shadow_root_level).
> 
> This is kinda wrong, and not consistent with existing non TDP MMU code.
> Fortuantely sp->role.level is only used in handle_removed_tdp_mmu_page()
> and kvm_tdp_mmu_zap_sp(), and they are already aware of this and behave
> correctly.  However to make it consistent with legacy MMU code (and fix
> the issue that both root page table and its child page table have
> shadow_root_level), use iter->level - 1 in kvm_tdp_mmu_map(), and change
> handle_removed_tdp_mmu_page() and kvm_tdp_mmu_zap_sp() accordingly.
> 
> Reviewed-by: Ben Gardon <bgardon@google.com>
> Signed-off-by: Kai Huang <kai.huang@intel.com>
> ---
>  arch/x86/kvm/mmu/tdp_mmu.c | 8 ++++----
>  arch/x86/kvm/mmu/tdp_mmu.h | 2 +-
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index c389d20418e3..a1db99d10680 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -335,7 +335,7 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt,
>  
> 
>  	for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
>  		sptep = rcu_dereference(pt) + i;
> -		gfn = base_gfn + (i * KVM_PAGES_PER_HPAGE(level - 1));
> +		gfn = base_gfn + i * KVM_PAGES_PER_HPAGE(level);
>  
> 
>  		if (shared) {
>  			/*
> @@ -377,12 +377,12 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt,
>  			WRITE_ONCE(*sptep, REMOVED_SPTE);
>  		}
>  		handle_changed_spte(kvm, kvm_mmu_page_as_id(sp), gfn,
> -				    old_child_spte, REMOVED_SPTE, level - 1,
> +				    old_child_spte, REMOVED_SPTE, level,
>  				    shared);
>  	}
>  
> 
>  	kvm_flush_remote_tlbs_with_address(kvm, gfn,
> -					   KVM_PAGES_PER_HPAGE(level));
> +					   KVM_PAGES_PER_HPAGE(level + 1));
>  
> 
>  	call_rcu(&sp->rcu_head, tdp_mmu_free_sp_rcu_callback);
>  }
> @@ -1013,7 +1013,7 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
>  		}
>  
> 
>  		if (!is_shadow_present_pte(iter.old_spte)) {
> -			sp = alloc_tdp_mmu_page(vcpu, iter.gfn, iter.level);
> +			sp = alloc_tdp_mmu_page(vcpu, iter.gfn, iter.level - 1);
>  			child_pt = sp->spt;
>  
> 
>  			new_spte = make_nonleaf_spte(child_pt,
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
> index 5fdf63090451..7f9974c5d0b4 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.h
> +++ b/arch/x86/kvm/mmu/tdp_mmu.h
> @@ -31,7 +31,7 @@ static inline bool kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id,
>  }
>  static inline bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
>  {
> -	gfn_t end = sp->gfn + KVM_PAGES_PER_HPAGE(sp->role.level);
> +	gfn_t end = sp->gfn + KVM_PAGES_PER_HPAGE(sp->role.level + 1);
>  
> 
>  	/*
>  	 * Don't allow yielding, as the caller may have a flush pending.  Note,



  reply	other threads:[~2021-05-06 23:46 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-06 23:33 [PATCH v2 0/3] TDP MMU: several minor fixes or improvements Kai Huang
2021-05-06 23:34 ` [PATCH v2 1/3] KVM: x86/mmu: Fix return value in tdp_mmu_map_handle_target_level() Kai Huang
2021-05-06 23:34 ` [PATCH v2 2/3] KVM: x86/mmu: Fix pf_fixed count " Kai Huang
2021-05-07 17:23   ` Sean Christopherson
2021-05-06 23:34 ` [PATCH v2 3/3] KVM: x86/mmu: Fix TDP MMU page table level Kai Huang
2021-05-06 23:46   ` Kai Huang [this message]
2021-05-27  2:03 ` [PATCH v2 0/3] TDP MMU: several minor fixes or improvements Kai Huang

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=6e9c2f0b6e36342ee4955178a92fa34c47c6de99.camel@intel.com \
    --to=kai.huang@intel.com \
    --cc=bgardon@google.com \
    --cc=jmattson@google.com \
    --cc=joro@8bytes.org \
    --cc=kvm@vger.kernel.org \
    --cc=pbonzini@redhat.com \
    --cc=seanjc@google.com \
    --cc=vkuznets@redhat.com \
    --cc=wanpengli@tencent.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).