From: Peter Xu <peterx@redhat.com>
To: Gavin Shan <gshan@redhat.com>
Cc: kvm@vger.kernel.org, linux-doc@vger.kernel.org,
catalin.marinas@arm.com, linux-kselftest@vger.kernel.org,
bgardon@google.com, shuah@kernel.org,
kvmarm@lists.cs.columbia.edu, corbet@lwn.net,
Marc Zyngier <maz@kernel.org>,
shan.gavin@gmail.com, drjones@redhat.com, will@kernel.org,
zhenyzha@redhat.com, dmatlack@google.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, pbonzini@redhat.com
Subject: Re: [PATCH v1 1/5] KVM: arm64: Enable ring-based dirty memory tracking
Date: Mon, 22 Aug 2022 14:55:55 -0400 [thread overview]
Message-ID: <YwPRO0r2sfzcbgyz@xz-m1.local> (raw)
In-Reply-To: <41fb5a1f-29a9-e6bb-9fab-4c83a2a8fce5@redhat.com>
Hi, Gavin,
On Mon, Aug 22, 2022 at 11:58:20AM +1000, Gavin Shan wrote:
> > For context, the documentation says:
> >
> > <quote>
> > - if KVM_CAP_DIRTY_LOG_RING is available, a number of pages at
> > KVM_DIRTY_LOG_PAGE_OFFSET * PAGE_SIZE. [...]
> > </quote>
> >
> > What is the reason for picking this particular value?
> >
>
> It's inherited from x86. I don't think it has to be this particular value.
> The value is used to distinguish the region's owners like kvm_run, KVM_PIO_PAGE_OFFSET,
> KVM_COALESCED_MMIO_PAGE_OFFSET, and KVM_DIRTY_LOG_PAGE_OFFSET.
>
> How about to have 2 for KVM_DIRTY_LOG_PAGE_OFFSET in next revision?
> The virtual area is cheap, I guess it's also nice to use x86's
> pattern to have 64 for KVM_DIRTY_LOG_PAGE_OFFSET.
>
> #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
> #define KVM_DIRTY_LOG_PAGE_OFFSET 2
It was chosen not to be continuous of previous used offset because it'll be
the 1st vcpu region that can cover multiple & dynamic number of pages. I
wanted to leave the 3-63 (x86 used offset 2 already) for small fields so
they can be continuous, which looks a little bit cleaner.
Currently how many pages it'll use depends on the size set by the user,
though there's a max size limited by KVM_DIRTY_RING_MAX_ENTRIES, which is a
maximum of 1MB memory.
So I think setting it to 2 is okay, as long as we keep the rest 1MB address
space for the per-vcpu ring structure, so any new vcpu fields (even if only
1 page will be needed) need to be after that maximum size of the ring.
Thanks,
--
Peter Xu
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
WARNING: multiple messages have this Message-ID (diff)
From: Peter Xu <peterx@redhat.com>
To: Gavin Shan <gshan@redhat.com>
Cc: Marc Zyngier <maz@kernel.org>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kselftest@vger.kernel.org, pbonzini@redhat.com,
corbet@lwn.net, james.morse@arm.com, alexandru.elisei@arm.com,
suzuki.poulose@arm.com, oliver.upton@linux.dev,
catalin.marinas@arm.com, will@kernel.org, shuah@kernel.org,
seanjc@google.com, drjones@redhat.com, dmatlack@google.com,
bgardon@google.com, ricarkol@google.com, zhenyzha@redhat.com,
shan.gavin@gmail.com
Subject: Re: [PATCH v1 1/5] KVM: arm64: Enable ring-based dirty memory tracking
Date: Mon, 22 Aug 2022 14:55:55 -0400 [thread overview]
Message-ID: <YwPRO0r2sfzcbgyz@xz-m1.local> (raw)
In-Reply-To: <41fb5a1f-29a9-e6bb-9fab-4c83a2a8fce5@redhat.com>
Hi, Gavin,
On Mon, Aug 22, 2022 at 11:58:20AM +1000, Gavin Shan wrote:
> > For context, the documentation says:
> >
> > <quote>
> > - if KVM_CAP_DIRTY_LOG_RING is available, a number of pages at
> > KVM_DIRTY_LOG_PAGE_OFFSET * PAGE_SIZE. [...]
> > </quote>
> >
> > What is the reason for picking this particular value?
> >
>
> It's inherited from x86. I don't think it has to be this particular value.
> The value is used to distinguish the region's owners like kvm_run, KVM_PIO_PAGE_OFFSET,
> KVM_COALESCED_MMIO_PAGE_OFFSET, and KVM_DIRTY_LOG_PAGE_OFFSET.
>
> How about to have 2 for KVM_DIRTY_LOG_PAGE_OFFSET in next revision?
> The virtual area is cheap, I guess it's also nice to use x86's
> pattern to have 64 for KVM_DIRTY_LOG_PAGE_OFFSET.
>
> #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
> #define KVM_DIRTY_LOG_PAGE_OFFSET 2
It was chosen not to be continuous of previous used offset because it'll be
the 1st vcpu region that can cover multiple & dynamic number of pages. I
wanted to leave the 3-63 (x86 used offset 2 already) for small fields so
they can be continuous, which looks a little bit cleaner.
Currently how many pages it'll use depends on the size set by the user,
though there's a max size limited by KVM_DIRTY_RING_MAX_ENTRIES, which is a
maximum of 1MB memory.
So I think setting it to 2 is okay, as long as we keep the rest 1MB address
space for the per-vcpu ring structure, so any new vcpu fields (even if only
1 page will be needed) need to be after that maximum size of the ring.
Thanks,
--
Peter Xu
WARNING: multiple messages have this Message-ID (diff)
From: Peter Xu <peterx@redhat.com>
To: Gavin Shan <gshan@redhat.com>
Cc: Marc Zyngier <maz@kernel.org>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kselftest@vger.kernel.org, pbonzini@redhat.com,
corbet@lwn.net, james.morse@arm.com, alexandru.elisei@arm.com,
suzuki.poulose@arm.com, oliver.upton@linux.dev,
catalin.marinas@arm.com, will@kernel.org, shuah@kernel.org,
seanjc@google.com, drjones@redhat.com, dmatlack@google.com,
bgardon@google.com, ricarkol@google.com, zhenyzha@redhat.com,
shan.gavin@gmail.com
Subject: Re: [PATCH v1 1/5] KVM: arm64: Enable ring-based dirty memory tracking
Date: Mon, 22 Aug 2022 14:55:55 -0400 [thread overview]
Message-ID: <YwPRO0r2sfzcbgyz@xz-m1.local> (raw)
In-Reply-To: <41fb5a1f-29a9-e6bb-9fab-4c83a2a8fce5@redhat.com>
Hi, Gavin,
On Mon, Aug 22, 2022 at 11:58:20AM +1000, Gavin Shan wrote:
> > For context, the documentation says:
> >
> > <quote>
> > - if KVM_CAP_DIRTY_LOG_RING is available, a number of pages at
> > KVM_DIRTY_LOG_PAGE_OFFSET * PAGE_SIZE. [...]
> > </quote>
> >
> > What is the reason for picking this particular value?
> >
>
> It's inherited from x86. I don't think it has to be this particular value.
> The value is used to distinguish the region's owners like kvm_run, KVM_PIO_PAGE_OFFSET,
> KVM_COALESCED_MMIO_PAGE_OFFSET, and KVM_DIRTY_LOG_PAGE_OFFSET.
>
> How about to have 2 for KVM_DIRTY_LOG_PAGE_OFFSET in next revision?
> The virtual area is cheap, I guess it's also nice to use x86's
> pattern to have 64 for KVM_DIRTY_LOG_PAGE_OFFSET.
>
> #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
> #define KVM_DIRTY_LOG_PAGE_OFFSET 2
It was chosen not to be continuous of previous used offset because it'll be
the 1st vcpu region that can cover multiple & dynamic number of pages. I
wanted to leave the 3-63 (x86 used offset 2 already) for small fields so
they can be continuous, which looks a little bit cleaner.
Currently how many pages it'll use depends on the size set by the user,
though there's a max size limited by KVM_DIRTY_RING_MAX_ENTRIES, which is a
maximum of 1MB memory.
So I think setting it to 2 is okay, as long as we keep the rest 1MB address
space for the per-vcpu ring structure, so any new vcpu fields (even if only
1 page will be needed) need to be after that maximum size of the ring.
Thanks,
--
Peter Xu
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-08-22 18:56 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-19 0:55 [PATCH v1 0/5] KVM: arm64: Enable ring-based dirty memory tracking Gavin Shan
2022-08-19 0:55 ` Gavin Shan
2022-08-19 0:55 ` Gavin Shan
2022-08-19 0:55 ` [PATCH v1 1/5] " Gavin Shan
2022-08-19 0:55 ` Gavin Shan
2022-08-19 0:55 ` Gavin Shan
2022-08-19 8:00 ` Marc Zyngier
2022-08-19 8:00 ` Marc Zyngier
2022-08-19 8:00 ` Marc Zyngier
2022-08-22 1:58 ` Gavin Shan
2022-08-22 1:58 ` Gavin Shan
2022-08-22 18:55 ` Peter Xu [this message]
2022-08-22 18:55 ` Peter Xu
2022-08-22 18:55 ` Peter Xu
2022-08-23 3:19 ` Gavin Shan
2022-08-23 3:19 ` Gavin Shan
2022-08-23 3:19 ` Gavin Shan
2022-08-22 21:42 ` Marc Zyngier
2022-08-22 21:42 ` Marc Zyngier
2022-08-22 21:42 ` Marc Zyngier
2022-08-23 5:22 ` Gavin Shan
2022-08-23 5:22 ` Gavin Shan
2022-08-23 5:22 ` Gavin Shan
2022-08-23 13:58 ` Peter Xu
2022-08-23 13:58 ` Peter Xu
2022-08-23 13:58 ` Peter Xu
2022-08-23 19:17 ` Marc Zyngier
2022-08-23 19:17 ` Marc Zyngier
2022-08-23 19:17 ` Marc Zyngier
2022-08-23 21:20 ` Peter Xu
2022-08-23 21:20 ` Peter Xu
2022-08-23 21:20 ` Peter Xu
2022-08-23 22:47 ` Marc Zyngier
2022-08-23 22:47 ` Marc Zyngier
2022-08-23 22:47 ` Marc Zyngier
2022-08-23 23:19 ` Peter Xu
2022-08-23 23:19 ` Peter Xu
2022-08-23 23:19 ` Peter Xu
2022-08-24 14:45 ` Marc Zyngier
2022-08-24 14:45 ` Marc Zyngier
2022-08-24 14:45 ` Marc Zyngier
2022-08-24 16:21 ` Peter Xu
2022-08-24 16:21 ` Peter Xu
2022-08-24 16:21 ` Peter Xu
2022-08-24 20:57 ` Marc Zyngier
2022-08-24 20:57 ` Marc Zyngier
2022-08-24 20:57 ` Marc Zyngier
2022-08-26 6:05 ` Gavin Shan
2022-08-26 6:05 ` Gavin Shan
2022-08-26 6:05 ` Gavin Shan
2022-08-26 10:50 ` Paolo Bonzini
2022-08-26 10:50 ` Paolo Bonzini
2022-08-26 10:50 ` Paolo Bonzini
2022-08-26 15:49 ` Marc Zyngier
2022-08-26 15:49 ` Marc Zyngier
2022-08-26 15:49 ` Marc Zyngier
2022-08-27 8:27 ` Paolo Bonzini
2022-08-27 8:27 ` Paolo Bonzini
2022-08-27 8:27 ` Paolo Bonzini
2022-08-29 10:27 ` Paolo Bonzini
2022-08-23 14:44 ` Oliver Upton
2022-08-23 14:44 ` Oliver Upton
2022-08-23 14:44 ` Oliver Upton
2022-08-23 20:35 ` Marc Zyngier
2022-08-23 20:35 ` Marc Zyngier
2022-08-23 20:35 ` Marc Zyngier
2022-08-26 10:58 ` Paolo Bonzini
2022-08-26 10:58 ` Paolo Bonzini
2022-08-26 10:58 ` Paolo Bonzini
2022-08-26 15:28 ` Marc Zyngier
2022-08-26 15:28 ` Marc Zyngier
2022-08-26 15:28 ` Marc Zyngier
2022-08-30 14:42 ` Peter Xu
2022-08-30 14:42 ` Peter Xu
2022-08-30 14:42 ` Peter Xu
2022-09-02 0:19 ` Paolo Bonzini
2022-09-02 0:19 ` Paolo Bonzini
2022-09-02 0:19 ` Paolo Bonzini
2022-08-19 0:55 ` [PATCH v1 2/5] KVM: selftests: Use host page size to map ring buffer in dirty_log_test Gavin Shan
2022-08-19 0:55 ` Gavin Shan
2022-08-19 0:55 ` Gavin Shan
2022-08-19 0:55 ` [PATCH v1 3/5] KVM: selftests: Dirty host pages " Gavin Shan
2022-08-19 0:55 ` Gavin Shan
2022-08-19 0:55 ` Gavin Shan
2022-08-19 5:28 ` Andrew Jones
2022-08-19 5:28 ` Andrew Jones
2022-08-19 5:28 ` Andrew Jones
2022-08-22 6:29 ` Gavin Shan
2022-08-22 6:29 ` Gavin Shan
2022-08-23 3:09 ` Gavin Shan
2022-08-23 3:09 ` Gavin Shan
2022-08-23 3:09 ` Gavin Shan
2022-08-19 0:56 ` [PATCH v1 4/5] KVM: selftests: Clear dirty ring states between two modes " Gavin Shan
2022-08-19 0:56 ` Gavin Shan
2022-08-19 0:56 ` Gavin Shan
2022-08-19 0:56 ` [PATCH v1 5/5] KVM: selftests: Automate choosing dirty ring size " Gavin Shan
2022-08-19 0:56 ` Gavin Shan
2022-08-19 0:56 ` Gavin Shan
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