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From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Cornelia Huck <cohuck@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Janosch Frank <frankja@linux.ibm.com>,
	kvm@vger.kernel.org, James Hogan <jhogan@kernel.org>,
	Joerg Roedel <joro@8bytes.org>,
	David Hildenbrand <david@redhat.com>,
	linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org,
	linux-kernel@vger.kernel.org, Paul Mackerras <paulus@ozlabs.org>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	linux-arm-kernel@lists.infradead.org,
	Marc Zyngier <maz@kernel.org>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	kvmarm@lists.cs.columbia.edu, Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH v2 14/15] KVM: Terminate memslot walks via used_slots
Date: Thu, 24 Oct 2019 22:24:09 +0200	[thread overview]
Message-ID: <5320341c-1abb-610b-8f5e-090a6726a9b1@redhat.com> (raw)
In-Reply-To: <20191024193856.GA28043@linux.intel.com>

On 24/10/19 21:38, Sean Christopherson wrote:
> only
>  * its new index into the array is update.

s/update/tracked/?

  Returns the changed memslot's
>  * current index into the memslots array.
>  */
> static inline int kvm_memslot_move_backward(struct kvm_memslots *slots,
> 					    struct kvm_memory_slot *memslot)
> {
> 	struct kvm_memory_slot *mslots = slots->memslots;
> 	int i;
> 
> 	if (WARN_ON_ONCE(slots->id_to_index[memslot->id] == -1) ||
> 	    WARN_ON_ONCE(!slots->used_slots))
> 		return -1;
> 
> 	for (i = slots->id_to_index[memslot->id]; i < slots->used_slots - 1; i++) {
> 		if (memslot->base_gfn > mslots[i + 1].base_gfn)
> 			break;
> 
> 		WARN_ON_ONCE(memslot->base_gfn == mslots[i + 1].base_gfn);
> 
> 		/* Shift the next memslot forward one and update its index. */
> 		mslots[i] = mslots[i + 1];
> 		slots->id_to_index[mslots[i].id] = i;
> 	}
> 	return i;
> }
> 
> /*
>  * Move a changed memslot forwards in the array by shifting existing slots with
>  * a lower GFN toward the back of the array.  Note, the changed memslot itself
>  * is not preserved in the array, i.e. not swapped at this time, only its new
>  * index into the array is updated

Same here?

>  * Note, slots are sorted from highest->lowest instead of lowest->highest for
>  * historical reasons.

Not just that, the largest slot (with all RAM above 4GB) is also often
at the highest address at least on x86.  But we could sort them by size
now, so I agree to call these historical reasons.

The code itself is fine, thanks for the work on documenting it.

Paolo

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  parent reply	other threads:[~2019-10-24 20:24 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-22  0:35 [PATCH v2 00/15] KVM: Dynamically size memslot arrays Sean Christopherson
2019-10-22  0:35 ` [PATCH v2 01/15] KVM: Reinstall old memslots if arch preparation fails Sean Christopherson
2019-10-23  9:29   ` Christoffer Dall
2019-10-22  0:35 ` [PATCH v2 02/15] KVM: Don't free new memslot if allocation of said memslot fails Sean Christopherson
2019-10-23  9:29   ` Christoffer Dall
2019-10-22  0:35 ` [PATCH v2 03/15] KVM: PPC: Move memslot memory allocation into prepare_memory_region() Sean Christopherson
2019-10-24 11:55   ` kbuild test robot
2019-10-22  0:35 ` [PATCH v2 04/15] KVM: x86: Allocate memslot resources during prepare_memory_region() Sean Christopherson
2019-10-22  0:35 ` [PATCH v2 05/15] KVM: Drop kvm_arch_create_memslot() Sean Christopherson
2019-10-22  0:35 ` [PATCH v2 06/15] KVM: Explicitly free allocated-but-unused dirty bitmap Sean Christopherson
2019-10-22  0:35 ` [PATCH v2 07/15] KVM: Refactor error handling for setting memory region Sean Christopherson
2019-10-22  0:35 ` [PATCH v2 08/15] KVM: Move setting of memslot into helper routine Sean Christopherson
2019-10-22  0:35 ` [PATCH v2 09/15] KVM: Move memslot deletion to helper function Sean Christopherson
2019-10-23  9:29   ` Christoffer Dall
2019-10-22  0:35 ` [PATCH v2 10/15] KVM: Simplify kvm_free_memslot() and all its descendents Sean Christopherson
2019-10-22  0:35 ` [PATCH v2 11/15] KVM: Clean up local variable usage in __kvm_set_memory_region() Sean Christopherson
2019-10-22  0:35 ` [PATCH v2 12/15] KVM: Provide common implementation for generic dirty log functions Sean Christopherson
2019-10-23  9:29   ` Christoffer Dall
2019-10-24 10:28   ` kbuild test robot
2019-10-22  0:35 ` [PATCH v2 13/15] KVM: Ensure validity of memslot with respect to kvm_get_dirty_log() Sean Christopherson
2019-10-22  0:35 ` [PATCH v2 14/15] KVM: Terminate memslot walks via used_slots Sean Christopherson
2019-10-22 14:04   ` Paolo Bonzini
2019-10-22 15:28     ` Sean Christopherson
2019-10-22 15:30       ` Paolo Bonzini
2019-10-22 15:52         ` Sean Christopherson
2019-10-22 15:53           ` Paolo Bonzini
2019-10-24 19:38             ` Sean Christopherson
2019-10-24 19:42               ` Sean Christopherson
2019-10-24 20:24               ` Paolo Bonzini [this message]
2019-10-24 20:48                 ` Sean Christopherson
2019-10-22  0:35 ` [PATCH v2 15/15] KVM: Dynamically size memslot array based on number of used slots Sean Christopherson
2019-10-22 14:04   ` Paolo Bonzini
2019-10-22 15:22     ` Sean Christopherson
2019-10-22 13:59 ` [PATCH v2 00/15] KVM: Dynamically size memslot arrays Paolo Bonzini
2019-10-23 18:56   ` Christian Borntraeger
2019-10-22 14:04 ` Paolo Bonzini
2019-10-23  9:39 ` Christoffer Dall

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