From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Peter Xu <peterx@redhat.com>
Cc: "James Hogan" <jhogan@kernel.org>,
"Paul Mackerras" <paulus@ozlabs.org>,
"Christian Borntraeger" <borntraeger@de.ibm.com>,
"Janosch Frank" <frankja@linux.ibm.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Marc Zyngier" <maz@kernel.org>,
linux-arm-kernel@lists.infradead.org,
"Wanpeng Li" <wanpengli@tencent.com>,
"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
kvm@vger.kernel.org, "David Hildenbrand" <david@redhat.com>,
"Joerg Roedel" <joro@8bytes.org>,
"Cornelia Huck" <cohuck@redhat.com>,
linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
kvm-ppc@vger.kernel.org, "Vitaly Kuznetsov" <vkuznets@redhat.com>,
kvmarm@lists.cs.columbia.edu, "Jim Mattson" <jmattson@google.com>
Subject: Re: [PATCH v4 16/19] KVM: Ensure validity of memslot with respect to kvm_get_dirty_log()
Date: Fri, 7 Feb 2020 10:52:47 -0800 [thread overview]
Message-ID: <20200207185247.GJ2401@linux.intel.com> (raw)
In-Reply-To: <20200206220355.GH700495@xz-x1>
On Thu, Feb 06, 2020 at 05:03:55PM -0500, Peter Xu wrote:
> On Tue, Jan 14, 2020 at 10:25:07AM -0800, Sean Christopherson wrote:
> > On Tue, Dec 24, 2019 at 01:19:30PM -0500, Peter Xu wrote:
> > > On Tue, Dec 17, 2019 at 12:40:38PM -0800, Sean Christopherson wrote:
> > > > +int kvm_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log,
> > > > + int *is_dirty, struct kvm_memory_slot **memslot)
> > > > {
> > > > struct kvm_memslots *slots;
> > > > - struct kvm_memory_slot *memslot;
> > > > int i, as_id, id;
> > > > unsigned long n;
> > > > unsigned long any = 0;
> > > >
> > > > + *memslot = NULL;
> > > > + *is_dirty = 0;
> > > > +
> > > > as_id = log->slot >> 16;
> > > > id = (u16)log->slot;
> > > > if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
> > > > return -EINVAL;
> > > >
> > > > slots = __kvm_memslots(kvm, as_id);
> > > > - memslot = id_to_memslot(slots, id);
> > > > - if (!memslot->dirty_bitmap)
> > > > + *memslot = id_to_memslot(slots, id);
> > > > + if (!(*memslot)->dirty_bitmap)
> > > > return -ENOENT;
> > > >
> > > > - n = kvm_dirty_bitmap_bytes(memslot);
> > > > + kvm_arch_sync_dirty_log(kvm, *memslot);
> > >
> > > Should this line belong to previous patch?
> >
> > No.
> >
> > The previous patch, "KVM: Provide common implementation for generic dirty
> > log functions", is consolidating the implementation of dirty log functions
> > for architectures with CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT=y.
> >
> > This code is being moved from s390's kvm_vm_ioctl_get_dirty_log(), as s390
> > doesn't select KVM_GENERIC_DIRTYLOG_READ_PROTECT. It's functionally a nop
> > as kvm_arch_sync_dirty_log() is empty for PowerPC, the only other arch that
> > doesn't select KVM_GENERIC_DIRTYLOG_READ_PROTECT.
> >
> > Arguably, the call to kvm_arch_sync_dirty_log() should be moved in a
> > separate prep patch. It can't be a follow-on patch as that would swap the
> > ordering of kvm_arch_sync_dirty_log() and kvm_dirty_bitmap_bytes(), etc...
> >
> > My reasoning for not splitting it to a separate patch is that prior to this
> > patch, the common code and arch specific code are doing separate memslot
> > lookups via id_to_memslot(), i.e. moving the kvm_arch_sync_dirty_log() call
> > would operate on a "different" memslot. It can't actually be a different
> > memslot because slots_lock is held, it just felt weird.
> >
> > All that being said, I don't have a strong opinion on moving the call to
> > kvm_arch_sync_dirty_log() in a separate patch; IIRC, I vascillated between
> > the two options when writing the code. If anyone wants it to be a separate
> > patch I'll happily split it out.
>
> (Sorry to respond so late)
>
> I think the confusing part is the subject, where you only mentioned
> the memslot change. IMHO you can split the change to make it clearer,
> or at least would you mind mention that kvm_arch_sync_dirty_log() move
> in the commit message? Thanks,
I'll add a few paragraphs to the changelog. Splitting it out still feels
weird.
next prev parent reply other threads:[~2020-02-07 18:52 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-17 20:40 [PATCH v4 00/19] KVM: Dynamically size memslot arrays Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 01/19] KVM: x86: Allocate new rmap and large page tracking when moving memslot Sean Christopherson
2019-12-17 20:48 ` Sean Christopherson
2019-12-17 20:50 ` Sean Christopherson
2019-12-17 21:56 ` Peter Xu
2019-12-17 22:20 ` Sean Christopherson
2019-12-17 22:37 ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 02/19] KVM: Reinstall old memslots if arch preparation fails Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 03/19] KVM: Don't free new memslot if allocation of said memslot fails Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 04/19] KVM: PPC: Move memslot memory allocation into prepare_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 05/19] KVM: x86: Allocate memslot resources during prepare_memory_region() Sean Christopherson
2019-12-17 22:07 ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 06/19] KVM: Drop kvm_arch_create_memslot() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 07/19] KVM: Explicitly free allocated-but-unused dirty bitmap Sean Christopherson
2019-12-17 22:24 ` Peter Xu
2019-12-17 22:51 ` Sean Christopherson
2019-12-18 16:17 ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 08/19] KVM: Refactor error handling for setting memory region Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 09/19] KVM: Move setting of memslot into helper routine Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 10/19] KVM: Drop "const" attribute from old memslot in commit_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 11/19] KVM: x86: Free arrays for old memslot when moving memslot's base gfn Sean Christopherson
2019-12-17 22:48 ` Peter Xu
2019-12-17 20:40 ` [PATCH v4 12/19] KVM: Move memslot deletion to helper function Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 13/19] KVM: Simplify kvm_free_memslot() and all its descendents Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 14/19] KVM: Clean up local variable usage in __kvm_set_memory_region() Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 15/19] KVM: Provide common implementation for generic dirty log functions Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 16/19] KVM: Ensure validity of memslot with respect to kvm_get_dirty_log() Sean Christopherson
2019-12-24 18:19 ` Peter Xu
2020-01-14 18:25 ` Sean Christopherson
2020-02-06 22:03 ` Peter Xu
2020-02-07 18:52 ` Sean Christopherson [this message]
2019-12-17 20:40 ` [PATCH v4 17/19] KVM: Terminate memslot walks via used_slots Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 18/19] KVM: Dynamically size memslot array based on number of used slots Sean Christopherson
2019-12-17 20:40 ` [PATCH v4 19/19] KVM: selftests: Add test for KVM_SET_USER_MEMORY_REGION Sean Christopherson
2019-12-18 11:29 ` Christian Borntraeger
2019-12-18 11:39 ` Christian Borntraeger
2019-12-18 16:39 ` Sean Christopherson
2020-03-24 9:43 ` Christian Borntraeger
2020-03-24 18:20 ` Sean Christopherson
2019-12-18 11:40 ` [PATCH v4 00/19] KVM: Dynamically size memslot arrays Christian Borntraeger
2019-12-18 18:10 ` Marc Zyngier
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