qemu-devel.nongnu.org archive mirror
 help / color / mirror / Atom feed
From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Xu <peterx@redhat.com>
Cc: qemu-stable@nongnu.org, qemu-devel@nongnu.org, dgilbert@redhat.com
Subject: Re: [PATCH 2/2] kvm: clear dirty bitmaps from all overlapping memslots
Date: Fri, 20 Sep 2019 16:03:00 +0200	[thread overview]
Message-ID: <09f006cf-d1ee-4639-50c8-cf8eb95d4fc2@redhat.com> (raw)
In-Reply-To: <20190920121813.GH12858@xz-x1>

On 20/09/19 14:18, Peter Xu wrote:
>   (1) memory region aliasing, hence multiple GPAs can point to the same
>       HVA/HPA so we need to clear the memslot dirty bits on all the
>       mapped GPAs, and,
> 
>   (2) large log_clear() request which can cover more than one valid
>       kvm memslots.  Note that in this case, the mem slots can really
>       be having different HVAs so imho it should be a different issue
>       comparing to (1)
> 
> The commit message says it's solving problem (1).  However for what I
> understand, we are actually doing well on issue (1) because in
> memory_region_clear_dirty_bitmap() we iterate over all the flat views
> so that we should have caught all the aliasing memory regions if there
> are any.

There could be two addresses pointing to the same HVA *in the same
flatview*.  See for example 0xe0000..0xfffff and 0xffffe000..0xffffffff
when a PC guest is started.  In this particular case
0xffffe000..0xffffffff is ROM, so it's not an issue, but in other cases
it may

> However this patch should perfectly fix problem (2).  Am I right?

I hadn't thought of problem (2).  I guess without Igor's work for s390
it does not exist?  But yes, it fixes it just the same.

Paolo


  reply	other threads:[~2019-09-20 14:05 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-20 10:21 [PATCH 0/2] kvm: clear dirty bitmaps from all overlapping memslots Paolo Bonzini
2019-09-20 10:21 ` [PATCH 1/2] kvm: extract kvm_log_clear_one_slot Paolo Bonzini
2019-09-20 12:11   ` Peter Xu
2019-09-20 10:21 ` [PATCH 2/2] kvm: clear dirty bitmaps from all overlapping memslots Paolo Bonzini
2019-09-20 12:18   ` Peter Xu
2019-09-20 14:03     ` Paolo Bonzini [this message]
2019-09-20 12:19 ` [PATCH 0/2] " Peter Xu
2019-09-20 13:58   ` Igor Mammedov
2019-09-23  1:29     ` Peter Xu
2019-09-23 16:15       ` Igor Mammedov
2019-09-23 16:49         ` Paolo Bonzini
2019-09-24  2:53           ` Peter Xu

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=09f006cf-d1ee-4639-50c8-cf8eb95d4fc2@redhat.com \
    --to=pbonzini@redhat.com \
    --cc=dgilbert@redhat.com \
    --cc=peterx@redhat.com \
    --cc=qemu-devel@nongnu.org \
    --cc=qemu-stable@nongnu.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).