From: Gavin Shan <gshan@redhat.com>
To: Andrew Jones <andrew.jones@linux.dev>
Cc: 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, peterx@redhat.com,
pbonzini@redhat.com, corbet@lwn.net, maz@kernel.org,
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 3/5] KVM: selftests: Dirty host pages in dirty_log_test
Date: Mon, 22 Aug 2022 16:29:52 +1000 [thread overview]
Message-ID: <3abb690f-e616-630f-ba40-e590ec8bb5c1@redhat.com> (raw)
In-Reply-To: <20220819052805.qnhw2d3arxixzvhl@kamzik>
Hi Drew,
On 8/19/22 3:28 PM, Andrew Jones wrote:
> On Fri, Aug 19, 2022 at 08:55:59AM +0800, Gavin Shan wrote:
>> It's assumed that 1024 host pages, instead of guest pages, are dirtied
>> in each iteration in guest_code(). The current implementation misses
>> the case of mismatched page sizes in host and guest. For example,
>> ARM64 could have 64KB page size in guest, but 4KB page size in host.
>> (TEST_PAGES_PER_LOOP / 16), instead of TEST_PAGES_PER_LOOP, host pages
>> are dirtied in every iteration.
>>
>> Fix the issue by touching all sub-pages when we have mismatched
>> page sizes in host and guest.
>
> I'll let the dirty-log test authors decide what's best to do for this
> test, but I'd think we should let the guest continue dirtying its
> pages without knowledge of the host pages. Then, adjust the host test
> code to assert all sub-pages, other than the ones it expects the guest
> to have written, remain untouched.
>
I don't think what is clarified in the change log is correct. The current
implementation already had the logic to handle the mismatched page sizes
in vm_dirty_log_verify() where 'step' is used for it by fetching value
from vm_num_host_pages(mode, 1). Please ignore this patch for now, as
explained below.
The issue I have is the 'dirty_log_test' hangs when I have 4KB host page size
and 64KB guest page size. It seems the vcpu doesn't exit due to full ring
buffer state or kick-off. I will have more investigations to figure out the
root cause.
# ./dirty_log_test -M dirty-ring -m 7
Setting log mode to: 'dirty-ring'
Test iterations: 32, interval: 10 (ms)
Testing guest mode: PA-bits:40, VA-bits:48, 64K pages
guest physical test memory offset: 0xffbffc0000
vcpu stops because vcpu is kicked out...
Notifying vcpu to continue
vcpu continues now.
Iteration 1 collected 1903 pages
<no more output>
'dirty_lot_test' works well when both host and guest have 4KB page size.
# ./dirty_log_test -M dirty-ring -m 5
Setting log mode to: 'dirty-ring'
Test iterations: 32, interval: 10 (ms)
Testing guest mode: PA-bits:40, VA-bits:48, 4K pages
guest physical test memory offset: 0xffbfffc000
vcpu stops because vcpu is kicked out...
Notifying vcpu to continue
vcpu continues now.
:
Dirtied 1006592 pages
Total bits checked: dirty (1020487), clear (7106070), track_next (974104)
Thanks,
Gavin
next prev parent reply other threads:[~2022-08-22 6:30 UTC|newest]
Thread overview: 33+ 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 ` [PATCH v1 1/5] " Gavin Shan
2022-08-19 8:00 ` Marc Zyngier
2022-08-22 1:58 ` Gavin Shan
2022-08-22 18:55 ` Peter Xu
2022-08-23 3:19 ` Gavin Shan
2022-08-22 21:42 ` Marc Zyngier
2022-08-23 5:22 ` Gavin Shan
2022-08-23 13:58 ` Peter Xu
2022-08-23 19:17 ` Marc Zyngier
2022-08-23 21:20 ` Peter Xu
2022-08-23 22:47 ` Marc Zyngier
2022-08-23 23:19 ` Peter Xu
2022-08-24 14:45 ` Marc Zyngier
2022-08-24 16:21 ` Peter Xu
2022-08-24 20:57 ` Marc Zyngier
2022-08-26 6:05 ` Gavin Shan
2022-08-26 10:50 ` Paolo Bonzini
2022-08-26 15:49 ` Marc Zyngier
2022-08-27 8:27 ` Paolo Bonzini
2022-08-23 14:44 ` Oliver Upton
2022-08-23 20:35 ` Marc Zyngier
2022-08-26 10:58 ` Paolo Bonzini
2022-08-26 15:28 ` Marc Zyngier
2022-08-30 14:42 ` Peter Xu
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 ` [PATCH v1 3/5] KVM: selftests: Dirty host pages " Gavin Shan
2022-08-19 5:28 ` Andrew Jones
2022-08-22 6:29 ` Gavin Shan [this message]
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 ` [PATCH v1 5/5] KVM: selftests: Automate choosing dirty ring size " Gavin Shan
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