From: Richard Henderson <richard.henderson@linaro.org>
To: Max Filippov <jcmvbkbc@gmail.com>, qemu-devel@nongnu.org
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Richard Henderson" <rth@twiddle.net>
Subject: Re: [PATCH 1/2] exec: flush CPU TB cache in breakpoint_invalidate
Date: Sun, 1 Dec 2019 15:48:55 -0800 [thread overview]
Message-ID: <3c02ba4a-11fe-4d6a-e6d9-f1d164528d85@linaro.org> (raw)
In-Reply-To: <20191127220602.10827-2-jcmvbkbc@gmail.com>
On 11/27/19 10:06 PM, Max Filippov wrote:
> When a breakpoint is inserted at location for which there's currently no
> virtual to physical translation no action is taken on CPU TB cache. If a
> TB for that virtual address already exists but is not visible ATM the
> breakpoint won't be hit next time an instruction at that address will be
> executed.
>
> Flush entire CPU TB cache in breakpoint_invalidate to force
> re-translation of all TBs for the breakpoint address.
>
> This change fixes the following scenario:
> - linux user application is running
> - a breakpoint is inserted from QEMU gdbstub for a user address that is
> not currently present in the target CPU TLB
> - an instruction at that address is executed, but the external debugger
> doesn't get control.
>
> Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
> ---
> Changes RFC->v1:
> - do tb_flush in breakpoint_invalidate unconditionally
Unlike Paolo, I don't think this is a good idea.
If I was going to change anything here, I'd change this to not use
cpu_get_phys_page_attrs_debug but using the caching available from the actual
cputlb, using cc->tlb_fill() in probe mode -- something akin to probe_access(),
but not returning a host address, nor handling watchpoints nor notdirty.
This would help flushing too much by distinguishing different tbs for the same
virtual address mapping to a different physical address.
r~
next prev parent reply other threads:[~2019-12-01 23:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 22:06 [PATCH 0/2] flush CPU TB cache in breakpoint_invalidate Max Filippov
2019-11-27 22:06 ` [PATCH 1/2] exec: " Max Filippov
2019-12-01 23:48 ` Richard Henderson [this message]
2019-12-03 11:16 ` Alex Bennée
2020-02-05 11:00 ` Richard Henderson
2020-02-05 21:14 ` Max Filippov
2019-11-27 22:06 ` [PATCH 2/2] exec: drop tb_invalidate_phys_addr Max Filippov
2019-12-01 23:53 ` Richard Henderson
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=3c02ba4a-11fe-4d6a-e6d9-f1d164528d85@linaro.org \
--to=richard.henderson@linaro.org \
--cc=alex.bennee@linaro.org \
--cc=jcmvbkbc@gmail.com \
--cc=pbonzini@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=rth@twiddle.net \
/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).