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From: Sean Christopherson <seanjc@google.com>
To: Wu Fei <atwufei@163.com>
Cc: wu.fei9@sanechips.com.cn, linux-riscv@lists.infradead.org,
	 linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	 kvm@vger.kernel.org, kvm-riscv@lists.infradead.org,
	anup@brainfault.org,  atish.patra@linux.dev, pjw@kernel.org,
	palmer@dabbelt.com,  aou@eecs.berkeley.edu, alex@ghiti.fr,
	pbonzini@redhat.com, shuah@kernel.org
Subject: Re: [PATCH 1/3] KVM: selftests: Add unit to dirty_log_test
Date: Mon, 18 May 2026 06:25:03 -0700	[thread overview]
Message-ID: <agsTL_viyxDjamX9@google.com> (raw)
In-Reply-To: <22e32ff9-3d79-4130-a3cb-3a4ec2efd498@163.com>

On Mon, May 18, 2026, Wu Fei wrote:
> On 5/15/26 21:51, Sean Christopherson wrote:
> > On Wed, May 13, 2026, Wu Fei wrote:
> > > On 5/13/26 08:03, Sean Christopherson wrote:
> > > > On Mon, May 11, 2026, wu.fei9@sanechips.com.cn wrote:
> > > > > 
> > > > > Unit is introduced to replace the default 1ms if specified in command
> > > > > line. The following test can't trigger failure on my riscv vm:
> > > > 
> > > > Failure of what?  And does the failure really not reproduce with a higher interval?
> > > 
> > > On riscv, it fails to write protect some pages with valid page table entry
> > > then loses track of dirty pages. Higher interval doesn't help because only
> > > the first usleep matters, after the first collect_dirty_pages, all dirty
> > > pages are tracked precisely then there is no such problem.
> > 
> > Ah, gotcha.  Rather than let (and force) the user to provide a larger sleep time,
> > what if we instead randomize the delay before the initial reaping of the dirty
> > bitmap/ring?  That should provide a good balance between coverage, complexity and
> > user-friendliness.
> 
> I'm fine with your solution, I applied it and it did trigger the same issue.

Awesome!  I'll post a patch today.

-- 
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WARNING: multiple messages have this Message-ID (diff)
From: Sean Christopherson <seanjc@google.com>
To: Wu Fei <atwufei@163.com>
Cc: wu.fei9@sanechips.com.cn, linux-riscv@lists.infradead.org,
	 linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	 kvm@vger.kernel.org, kvm-riscv@lists.infradead.org,
	anup@brainfault.org,  atish.patra@linux.dev, pjw@kernel.org,
	palmer@dabbelt.com,  aou@eecs.berkeley.edu, alex@ghiti.fr,
	pbonzini@redhat.com, shuah@kernel.org
Subject: Re: [PATCH 1/3] KVM: selftests: Add unit to dirty_log_test
Date: Mon, 18 May 2026 06:25:03 -0700	[thread overview]
Message-ID: <agsTL_viyxDjamX9@google.com> (raw)
In-Reply-To: <22e32ff9-3d79-4130-a3cb-3a4ec2efd498@163.com>

On Mon, May 18, 2026, Wu Fei wrote:
> On 5/15/26 21:51, Sean Christopherson wrote:
> > On Wed, May 13, 2026, Wu Fei wrote:
> > > On 5/13/26 08:03, Sean Christopherson wrote:
> > > > On Mon, May 11, 2026, wu.fei9@sanechips.com.cn wrote:
> > > > > 
> > > > > Unit is introduced to replace the default 1ms if specified in command
> > > > > line. The following test can't trigger failure on my riscv vm:
> > > > 
> > > > Failure of what?  And does the failure really not reproduce with a higher interval?
> > > 
> > > On riscv, it fails to write protect some pages with valid page table entry
> > > then loses track of dirty pages. Higher interval doesn't help because only
> > > the first usleep matters, after the first collect_dirty_pages, all dirty
> > > pages are tracked precisely then there is no such problem.
> > 
> > Ah, gotcha.  Rather than let (and force) the user to provide a larger sleep time,
> > what if we instead randomize the delay before the initial reaping of the dirty
> > bitmap/ring?  That should provide a good balance between coverage, complexity and
> > user-friendliness.
> 
> I'm fine with your solution, I applied it and it did trigger the same issue.

Awesome!  I'll post a patch today.

WARNING: multiple messages have this Message-ID (diff)
From: Sean Christopherson <seanjc@google.com>
To: Wu Fei <atwufei@163.com>
Cc: wu.fei9@sanechips.com.cn, linux-riscv@lists.infradead.org,
	 linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	 kvm@vger.kernel.org, kvm-riscv@lists.infradead.org,
	anup@brainfault.org,  atish.patra@linux.dev, pjw@kernel.org,
	palmer@dabbelt.com,  aou@eecs.berkeley.edu, alex@ghiti.fr,
	pbonzini@redhat.com, shuah@kernel.org
Subject: Re: [PATCH 1/3] KVM: selftests: Add unit to dirty_log_test
Date: Mon, 18 May 2026 06:25:03 -0700	[thread overview]
Message-ID: <agsTL_viyxDjamX9@google.com> (raw)
In-Reply-To: <22e32ff9-3d79-4130-a3cb-3a4ec2efd498@163.com>

On Mon, May 18, 2026, Wu Fei wrote:
> On 5/15/26 21:51, Sean Christopherson wrote:
> > On Wed, May 13, 2026, Wu Fei wrote:
> > > On 5/13/26 08:03, Sean Christopherson wrote:
> > > > On Mon, May 11, 2026, wu.fei9@sanechips.com.cn wrote:
> > > > > 
> > > > > Unit is introduced to replace the default 1ms if specified in command
> > > > > line. The following test can't trigger failure on my riscv vm:
> > > > 
> > > > Failure of what?  And does the failure really not reproduce with a higher interval?
> > > 
> > > On riscv, it fails to write protect some pages with valid page table entry
> > > then loses track of dirty pages. Higher interval doesn't help because only
> > > the first usleep matters, after the first collect_dirty_pages, all dirty
> > > pages are tracked precisely then there is no such problem.
> > 
> > Ah, gotcha.  Rather than let (and force) the user to provide a larger sleep time,
> > what if we instead randomize the delay before the initial reaping of the dirty
> > bitmap/ring?  That should provide a good balance between coverage, complexity and
> > user-friendliness.
> 
> I'm fine with your solution, I applied it and it did trigger the same issue.

Awesome!  I'll post a patch today.

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

  reply	other threads:[~2026-05-18 13:25 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <202605111849442561v1a0B_7W1L2Z-ENusLaP@zte.com.cn>
2026-05-11 11:23 ` [PATCH 1/3] KVM: selftests: Add unit to dirty_log_test wu.fei9
2026-05-11 11:23   ` wu.fei9
2026-05-11 11:23   ` wu.fei9
2026-05-13  0:03   ` Sean Christopherson
2026-05-13  0:03     ` Sean Christopherson
2026-05-13  0:03     ` Sean Christopherson
2026-05-13 12:27     ` Wu Fei
2026-05-13 12:27       ` Wu Fei
2026-05-13 12:27       ` Wu Fei
2026-05-15 13:51       ` Sean Christopherson
2026-05-15 13:51         ` Sean Christopherson
2026-05-15 13:51         ` Sean Christopherson
2026-05-18 12:52         ` Wu Fei
2026-05-18 12:52           ` Wu Fei
2026-05-18 12:52           ` Wu Fei
2026-05-18 13:25           ` Sean Christopherson [this message]
2026-05-18 13:25             ` Sean Christopherson
2026-05-18 13:25             ` Sean Christopherson
2026-05-11 11:24 ` [PATCH 2/3] RISC-V: KVM: Fix skip of valid pages in kvm_riscv_gstage_wp_range wu.fei9
2026-05-11 11:24   ` wu.fei9
2026-05-11 11:24   ` wu.fei9
2026-06-02  8:00   ` Anup Patel
2026-06-02  8:00     ` Anup Patel
2026-06-02  8:00     ` Anup Patel
2026-05-11 11:29 ` [PATCH 3/3] RISC-V: KVM: Fix skip of valid pages in kvm_riscv_gstage_unmap_range wu.fei9
2026-05-11 11:29   ` wu.fei9
2026-05-11 11:29   ` wu.fei9

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