All of lore.kernel.org
 help / color / mirror / Atom feed
From: Sean Christopherson <seanjc@google.com>
To: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Cc: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	David Hildenbrand <david@redhat.com>,
	Maxim Levitsky <mlevitsk@redhat.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 0/9] kvm: implement atomic memslot updates
Date: Fri, 9 Sep 2022 14:30:42 +0000	[thread overview]
Message-ID: <YxtOEgJhe4EcAJsE@google.com> (raw)
In-Reply-To: <20220909104506.738478-1-eesposit@redhat.com>

On Fri, Sep 09, 2022, Emanuele Giuseppe Esposito wrote:
> KVM is currently capable of receiving a single memslot update through
> the KVM_SET_USER_MEMORY_REGION ioctl.
> The problem arises when we want to atomically perform multiple updates,
> so that readers of memslot active list avoid seeing incomplete states.
> 
> For example, in RHBZ https://bugzilla.redhat.com/show_bug.cgi?id=1979276

I don't have access.  Can you provide a TL;DR?

> we see how non atomic updates cause boot failure, because vcpus
> will se a partial update (old memslot delete, new one not yet created)
> and will crash.

Why not simply pause vCPUs in this scenario?  This is an awful lot of a complexity
to take on for something that appears to be solvable in userspace. 

And if the issue is related to KVM disallowing the toggling of read-only (can't see
the bug), we can likely solve that without needing a new ioctl() that allows
userspace to batch an arbitrary number of updates.

  parent reply	other threads:[~2022-09-09 14:31 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-09 10:44 [RFC PATCH 0/9] kvm: implement atomic memslot updates Emanuele Giuseppe Esposito
2022-09-09 10:44 ` [RFC PATCH 1/9] kvm_main.c: move slot check in kvm_set_memory_region Emanuele Giuseppe Esposito
2022-09-28 16:41   ` Paolo Bonzini
2022-09-09 10:44 ` [RFC PATCH 2/9] kvm.h: introduce KVM_SET_USER_MEMORY_REGION_LIST ioctl Emanuele Giuseppe Esposito
2022-09-28 16:42   ` Paolo Bonzini
2022-09-09 10:45 ` [RFC PATCH 3/9] kvm_main.c: introduce kvm_internal_memory_region_list Emanuele Giuseppe Esposito
2022-09-28 16:48   ` Paolo Bonzini
2022-09-09 10:45 ` [RFC PATCH 4/9] kvm_main.c: split logic in kvm_set_memslots Emanuele Giuseppe Esposito
2022-09-28 17:04   ` Paolo Bonzini
2022-09-09 10:45 ` [RFC PATCH 5/9] kvm_main.c: split __kvm_set_memory_region logic in kvm_check_mem and kvm_prepare_batch Emanuele Giuseppe Esposito
2022-09-13  2:56   ` Yang, Weijiang
2022-09-18 16:22     ` Emanuele Giuseppe Esposito
2022-09-28 17:11   ` Paolo Bonzini
2022-09-09 10:45 ` [RFC PATCH 6/9] kvm_main.c: simplify change-specific callbacks Emanuele Giuseppe Esposito
2022-09-09 10:45 ` [RFC PATCH 7/9] kvm_main.c: duplicate invalid memslot also in inactive list Emanuele Giuseppe Esposito
2022-09-28 17:18   ` Paolo Bonzini
2022-09-09 10:45 ` [RFC PATCH 8/9] kvm_main.c: find memslots from the inactive memslot list Emanuele Giuseppe Esposito
2022-09-09 10:45 ` [RFC PATCH 9/9] kvm_main.c: handle atomic memslot update Emanuele Giuseppe Esposito
2022-09-13  2:30   ` Yang, Weijiang
2022-09-18 16:18     ` Emanuele Giuseppe Esposito
2022-09-27  7:46   ` David Hildenbrand
2022-09-27  8:35     ` Emanuele Giuseppe Esposito
2022-09-27  9:22       ` David Hildenbrand
2022-09-27  9:32         ` Emanuele Giuseppe Esposito
2022-09-27 14:52           ` David Hildenbrand
2022-09-28 17:29   ` Paolo Bonzini
2022-09-09 14:30 ` Sean Christopherson [this message]
2022-09-18 16:13   ` [RFC PATCH 0/9] kvm: implement atomic memslot updates Emanuele Giuseppe Esposito
2022-09-19  7:38     ` Like Xu
2022-09-19  7:53     ` David Hildenbrand
2022-09-19 17:30       ` David Hildenbrand
2022-09-23 13:10         ` Emanuele Giuseppe Esposito
2022-09-23 13:21           ` David Hildenbrand
2022-09-23 13:38             ` Emanuele Giuseppe Esposito
2022-09-26  9:03               ` David Hildenbrand
2022-09-26 21:28                 ` Sean Christopherson
2022-09-27  7:38                   ` Emanuele Giuseppe Esposito
2022-09-27 15:58                     ` Sean Christopherson
2022-09-28  9:11                       ` Emanuele Giuseppe Esposito
2022-09-28 11:14                         ` Maxim Levitsky
2022-09-28 12:52                           ` David Hildenbrand
2022-09-28 15:07                       ` Paolo Bonzini
2022-09-28 15:33                         ` David Hildenbrand
2022-09-28 15:58                         ` Sean Christopherson
2022-09-28 16:38                           ` Paolo Bonzini
2022-09-28 20:41                             ` Sean Christopherson
2022-09-29  8:05                               ` Emanuele Giuseppe Esposito
2022-09-29  8:24                                 ` David Hildenbrand
2022-09-29 15:18                                 ` Sean Christopherson
2022-09-29 15:41                                   ` Paolo Bonzini
2022-09-29 15:28                               ` Paolo Bonzini
2022-09-29 15:40                                 ` Maxim Levitsky
2022-09-29 16:00                                 ` David Hildenbrand
2022-09-29 21:39                                 ` Sean Christopherson
2022-10-13  7:43                                   ` Emanuele Giuseppe Esposito
2022-10-13  8:44                                     ` David Hildenbrand
2022-10-13 11:12                                       ` Emanuele Giuseppe Esposito
2022-10-13 14:45                                         ` David Hildenbrand

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=YxtOEgJhe4EcAJsE@google.com \
    --to=seanjc@google.com \
    --cc=bp@alien8.de \
    --cc=dave.hansen@linux.intel.com \
    --cc=david@redhat.com \
    --cc=eesposit@redhat.com \
    --cc=hpa@zytor.com \
    --cc=jmattson@google.com \
    --cc=joro@8bytes.org \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=mlevitsk@redhat.com \
    --cc=pbonzini@redhat.com \
    --cc=tglx@linutronix.de \
    --cc=vkuznets@redhat.com \
    --cc=wanpengli@tencent.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.