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From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ben Gardon <bgardon@google.com>,
	Makarand Sonare <makarandsonare@google.com>
Subject: Re: [PATCH 10/14] KVM: x86: Further clarify the logic and comments for toggling log dirty
Date: Thu, 18 Feb 2021 08:15:10 -0800	[thread overview]
Message-ID: <YC6SjgYTi+Dr1l0d@google.com> (raw)
In-Reply-To: <2d455c2e-1db4-5aff-45eb-529e68127fe7@redhat.com>

On Thu, Feb 18, 2021, Paolo Bonzini wrote:
> On 13/02/21 01:50, Sean Christopherson wrote:
> > 
> > -	 * Nothing to do for RO slots or CREATE/MOVE/DELETE of a slot.
> > -	 * See comments below.
> > +	 * Nothing to do for RO slots (which can't be dirtied and can't be made
> > +	 * writable) or CREATE/MOVE/DELETE of a slot.  See comments below.
> >  	 */
> >  	if ((change != KVM_MR_FLAGS_ONLY) || (new->flags & KVM_MEM_READONLY))
> >  		return;
> > +	/*
> > +	 * READONLY and non-flags changes were filtered out above, and the only
> > +	 * other flag is LOG_DIRTY_PAGES, i.e. something is wrong if dirty
> > +	 * logging isn't being toggled on or off.
> > +	 */
> > +	if (WARN_ON_ONCE(!((old->flags ^ new->flags) & KVM_MEM_LOG_DIRTY_PAGES)))
> > +		return;
> > +
> 
> What about readonly -> readwrite changes?

Not allowed without first deleting the memslot.  See commit 75d61fbcf563 ("KVM:
set_memory_region: Disallow changing read-only attribute later").  RW->RO is
also not supported.

	if (!old.npages) {
		change = KVM_MR_CREATE;
		new.dirty_bitmap = NULL;
		memset(&new.arch, 0, sizeof(new.arch));
	} else { /* Modify an existing slot. */
		if ((new.userspace_addr != old.userspace_addr) ||
		    (new.npages != old.npages) ||
		    ((new.flags ^ old.flags) & KVM_MEM_READONLY))
			return -EINVAL;


  reply	other threads:[~2021-02-18 18:40 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-13  0:50 [PATCH 00/14] KVM: x86/mmu: Dirty logging fixes and improvements Sean Christopherson
2021-02-13  0:50 ` [PATCH 01/14] KVM: x86/mmu: Expand collapsible SPTE zap for TDP MMU to ZONE_DEVICE pages Sean Christopherson
2021-02-18 12:36   ` Paolo Bonzini
2021-02-13  0:50 ` [PATCH 02/14] KVM: x86/mmu: Don't unnecessarily write-protect small pages in TDP MMU Sean Christopherson
2021-02-13  0:50 ` [PATCH 03/14] KVM: x86/mmu: Split out max mapping level calculation to helper Sean Christopherson
2021-02-13  0:50 ` [PATCH 04/14] KVM: x86/mmu: Pass the memslot to the rmap callbacks Sean Christopherson
2021-02-13  0:50 ` [PATCH 05/14] KVM: x86/mmu: Consult max mapping level when zapping collapsible SPTEs Sean Christopherson
2021-02-18 12:43   ` Paolo Bonzini
2021-02-18 16:23     ` Sean Christopherson
2021-02-18 22:30       ` Mike Kravetz
2021-02-19  1:31         ` Sean Christopherson
2021-02-13  0:50 ` [PATCH 06/14] KVM: nVMX: Disable PML in hardware when running L2 Sean Christopherson
2021-02-13  0:50 ` [PATCH 07/14] KVM: x86/mmu: Expand on the comment in kvm_vcpu_ad_need_write_protect() Sean Christopherson
2021-02-13  0:50 ` [PATCH 08/14] KVM: x86/mmu: Make dirty log size hook (PML) a value, not a function Sean Christopherson
2021-02-18 12:45   ` Paolo Bonzini
2021-02-13  0:50 ` [PATCH 09/14] KVM: x86: Move MMU's PML logic to common code Sean Christopherson
2021-02-13  0:50 ` [PATCH 10/14] KVM: x86: Further clarify the logic and comments for toggling log dirty Sean Christopherson
2021-02-18 12:50   ` Paolo Bonzini
2021-02-18 16:15     ` Sean Christopherson [this message]
2021-02-18 16:56       ` Paolo Bonzini
2021-02-13  0:50 ` [PATCH 11/14] KVM: VMX: Dynamically enable/disable PML based on memslot dirty logging Sean Christopherson
2021-02-13  0:50 ` [PATCH 12/14] KVM: x86/mmu: Don't set dirty bits when disabling dirty logging w/ PML Sean Christopherson
2021-02-18 17:08   ` Paolo Bonzini
2021-02-13  0:50 ` [PATCH 13/14] KVM: x86: Fold "write-protect large" use case into generic write-protect Sean Christopherson
2021-02-13  0:50 ` [PATCH 14/14] KVM: x86/mmu: Remove a variety of unnecessary exports Sean Christopherson
2021-02-17 22:50 ` [PATCH 00/14] KVM: x86/mmu: Dirty logging fixes and improvements Sean Christopherson
2021-02-18 12:57 ` Paolo Bonzini

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