From: Steven Rostedt <rostedt@goodmis.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Joel Fernandes <joel@joelfernandes.org>,
Vineeth Remanan Pillai <vineeth@bitbyteword.org>,
Ben Segall <bsegall@google.com>, Borislav Petkov <bp@alien8.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
"H . Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>, Mel Gorman <mgorman@suse.de>,
Paolo Bonzini <pbonzini@redhat.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Valentin Schneider <vschneid@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Suleiman Souhlal <suleiman@google.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
himadrics@inria.fr, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, x86@kernel.org, graf@amazon.com,
drjunior.org@gmail.com
Subject: Re: [RFC PATCH v2 0/5] Paravirt Scheduling (Dynamic vcpu priority management)
Date: Fri, 12 Jul 2024 13:02:28 -0400 [thread overview]
Message-ID: <20240712130228.72de0a7d@rorschach.local.home> (raw)
In-Reply-To: <ZpFcWPMwEOQchvCB@google.com>
On Fri, 12 Jul 2024 09:39:52 -0700
Sean Christopherson <seanjc@google.com> wrote:
> >
> > One other issue we need to worry about is that IIUC rseq memory is
> > allocated by the guest/user, not the host kernel. This means it can be
> > swapped out. The code that handles this needs to be able to handle user
> > page faults.
>
> This is a non-issue, it will Just Work, same as any other memory that is exposed
> to the guest and can be reclaimed/swapped/migrated..
>
> If the host swaps out the rseq page, mmu_notifiers will call into KVM and KVM will
> unmap the page from the guest. If/when the page is accessed by the guest, KVM
> will fault the page back into the host's primary MMU, and then map the new pfn
> into the guest.
My comment is that in the host kernel, the access to this memory needs
to be user page fault safe. You can't call it in atomic context.
-- Steve
next prev parent reply other threads:[~2024-07-12 17:02 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-03 14:01 [RFC PATCH v2 0/5] Paravirt Scheduling (Dynamic vcpu priority management) Vineeth Pillai (Google)
2024-04-03 14:01 ` [RFC PATCH v2 1/5] pvsched: paravirt scheduling framework Vineeth Pillai (Google)
2024-04-08 13:57 ` Vineeth Remanan Pillai
2024-04-03 14:01 ` [RFC PATCH v2 2/5] kvm: Implement the paravirt sched framework for kvm Vineeth Pillai (Google)
2024-04-08 13:58 ` Vineeth Remanan Pillai
2024-04-03 14:01 ` [RFC PATCH v2 3/5] kvm: interface for managing pvsched driver for guest VMs Vineeth Pillai (Google)
2024-04-08 13:59 ` Vineeth Remanan Pillai
2024-04-03 14:01 ` [RFC PATCH v2 4/5] pvsched: bpf support for pvsched Vineeth Pillai (Google)
2024-04-08 14:00 ` Vineeth Remanan Pillai
2024-04-03 14:01 ` [RFC PATCH v2 5/5] selftests/bpf: sample implementation of a bpf pvsched driver Vineeth Pillai (Google)
2024-04-08 14:01 ` Vineeth Remanan Pillai
2024-04-08 13:54 ` [RFC PATCH v2 0/5] Paravirt Scheduling (Dynamic vcpu priority management) Vineeth Remanan Pillai
2024-05-01 15:29 ` Sean Christopherson
2024-05-02 13:42 ` Vineeth Remanan Pillai
2024-06-24 11:01 ` Vineeth Remanan Pillai
2024-07-12 12:57 ` Joel Fernandes
2024-07-12 14:09 ` Mathieu Desnoyers
2024-07-12 14:48 ` Sean Christopherson
2024-07-12 15:32 ` Mathieu Desnoyers
2024-07-12 16:14 ` Sean Christopherson
2024-07-12 16:30 ` Steven Rostedt
2024-07-12 16:39 ` Sean Christopherson
2024-07-12 17:02 ` Steven Rostedt [this message]
2024-07-12 16:24 ` Steven Rostedt
2024-07-12 16:44 ` Sean Christopherson
2024-07-12 16:50 ` Joel Fernandes
2024-07-12 17:08 ` Sean Christopherson
2024-07-12 17:14 ` Steven Rostedt
2024-07-12 17:12 ` Steven Rostedt
2024-07-16 23:44 ` Sean Christopherson
2024-07-17 0:13 ` Steven Rostedt
2024-07-17 5:16 ` Joel Fernandes
2024-07-17 14:14 ` Sean Christopherson
2024-07-17 14:36 ` Steven Rostedt
2024-07-17 14:52 ` Steven Rostedt
2024-07-17 15:20 ` Steven Rostedt
2024-07-17 17:03 ` Suleiman Souhlal
2024-07-17 20:57 ` Joel Fernandes
2024-07-17 21:00 ` Steven Rostedt
2024-07-17 21:09 ` Joel Fernandes
2024-07-12 16:24 ` Joel Fernandes
2024-07-12 17:28 ` Mathieu Desnoyers
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