From: Sean Christopherson <seanjc@google.com>
To: Marco Marangoni <mamarang@amazon.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-patches@amazon.com, mancio@amazon.co.uk,
zoumboul@amazon.com
Subject: Re: [RFC] KVM: x86/mmu: Prefetch forward run of pages on TDP page faults
Date: Tue, 25 Aug 2026 08:00:29 -0700 [thread overview]
Message-ID: <ao2uDa91H66vJizu@google.com> (raw)
In-Reply-To: <20260825140159.70997-1-mamarang@amazon.com>
On Tue, Aug 25, 2026, Marco Marangoni wrote:
> It's worth mentioning that I also evaluated using the existing
> KVM_PRE_FAULT_MEMORY ioctl, but this doesn't work well for our use-case, as
> it requires the vCPU to be paused.
What about if/when KVM Userfault[*] comes along? I.e. pre-fault memory when the
vCPU exits to userspace.
If KVM Userfault + KVM_PRE_FAULT_MEMORY is viable for Firecracker and provides
the desired performance, I would strongly prefer that approach over KVM doing its
own prefetching. That way other architectures don't need to implement prefetching
as well (arm64 already supports KVM_PRE_FAULT_MEMORY, and RISC-V has patches posted).
I'm aiming to get back to that series "soon", this would simply be more motivation
to get KVM Userfault landed.
[*] https://lore.kernel.org/all/20250618042424.330664-1-jthoughton@google.com
next prev parent reply other threads:[~2026-08-25 15:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-25 14:01 [RFC] KVM: x86/mmu: Prefetch forward run of pages on TDP page faults Marco Marangoni
2026-08-25 14:18 ` sashiko-bot
2026-08-25 15:00 ` Sean Christopherson [this message]
2026-08-25 15:54 ` James Houghton
2026-08-27 13:31 ` Thomson, Jack
2026-08-25 15:59 ` James Houghton
2026-08-25 17:38 ` Marangoni, Marco
2026-08-25 18:06 ` James Houghton
2026-08-25 20:55 ` Marangoni, Marco
2026-08-25 21:01 ` Sean Christopherson
2026-08-25 21:04 ` Sean Christopherson
2026-08-25 21:40 ` Sean Christopherson
2026-08-25 22:33 ` Marangoni, Marco
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