From: Jan Beulich <jbeulich@suse.com>
To: Roger Pau Monne <roger.pau@citrix.com>
Cc: Shawn Anastasio <sanastasio@raptorengineering.com>,
Alistair Francis <alistair.francis@wdc.com>,
Bob Eshleman <bobbyeshleman@gmail.com>,
Connor Davis <connojdavis@gmail.com>,
Oleksii Kurochko <oleksii.kurochko@gmail.com>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH for-4.19] ppc/riscv: fix arch_acquire_resource_check()
Date: Thu, 2 May 2024 09:23:30 +0200 [thread overview]
Message-ID: <0f39a067-70d2-4652-910a-5d05db6a3ebc@suse.com> (raw)
In-Reply-To: <20240430153423.80875-1-roger.pau@citrix.com>
On 30.04.2024 17:34, Roger Pau Monne wrote:
> None of the implementations support set_foreign_p2m_entry() yet, neither they
> have a p2m walk in domain_relinquish_resources() in order to remove the foreign
> mappings from the p2m and thus drop the extra refcounts.
While I don't mind the cod adjustment into the more safe direction, I find
this justification odd: RISC-V has no domain_relinquish_resources() at all
right now, and PPC has it properly as a stub only. Judgement on what there
is (or not) can only be made one non-stub implementations exist.
IOW provided PPC and RISC-V people agree, I'm fine putting this in, but
preferably with an adjusted description. To be honest with how you put it,
it's not even really clear to me what (practical) problem, if any, you're
trying to address.
Jan
> Adjust the arch helpers to return false and introduce a comment that clearly
> states it is not only taking extra refcounts that's needed, but also dropping
> them on domain teardown.
>
> Fixes: 4988704e00d8 ('xen/riscv: introduce p2m.h')
> Fixes: 4a2f68f90930 ('xen/ppc: Define minimal stub headers required for full build')
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> ---
> xen/arch/ppc/include/asm/p2m.h | 7 ++++---
> xen/arch/riscv/include/asm/p2m.h | 7 ++++---
> 2 files changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/xen/arch/ppc/include/asm/p2m.h b/xen/arch/ppc/include/asm/p2m.h
> index 25ba05466853..f144ef8e1a54 100644
> --- a/xen/arch/ppc/include/asm/p2m.h
> +++ b/xen/arch/ppc/include/asm/p2m.h
> @@ -81,10 +81,11 @@ static inline mfn_t gfn_to_mfn(struct domain *d, gfn_t gfn)
> static inline bool arch_acquire_resource_check(struct domain *d)
> {
> /*
> - * The reference counting of foreign entries in set_foreign_p2m_entry()
> - * is supported on PPC.
> + * Requires refcounting the foreign mappings and walking the p2m on
> + * teardown in order to remove foreign pages from the p2m and drop the
> + * extra reference counts.
> */
> - return true;
> + return false;
> }
>
> static inline void p2m_altp2m_check(struct vcpu *v, uint16_t idx)
> diff --git a/xen/arch/riscv/include/asm/p2m.h b/xen/arch/riscv/include/asm/p2m.h
> index 87b13f897926..387f372b5d26 100644
> --- a/xen/arch/riscv/include/asm/p2m.h
> +++ b/xen/arch/riscv/include/asm/p2m.h
> @@ -79,10 +79,11 @@ static inline mfn_t gfn_to_mfn(struct domain *d, gfn_t gfn)
> static inline bool arch_acquire_resource_check(struct domain *d)
> {
> /*
> - * The reference counting of foreign entries in set_foreign_p2m_entry()
> - * is supported on RISCV.
> + * Requires refcounting the foreign mappings and walking the p2m on
> + * teardown in order to remove foreign pages from the p2m and drop the
> + * extra reference counts.
> */
> - return true;
> + return false;
> }
>
> static inline void p2m_altp2m_check(struct vcpu *v, uint16_t idx)
next prev parent reply other threads:[~2024-05-02 7:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-30 15:34 [PATCH for-4.19] ppc/riscv: fix arch_acquire_resource_check() Roger Pau Monne
2024-05-02 7:23 ` Jan Beulich [this message]
2024-05-02 7:35 ` Roger Pau Monné
2024-05-02 8:46 ` Oleksii
2024-05-02 10:31 ` Roger Pau Monné
2024-05-05 22:12 ` Shawn Anastasio
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=0f39a067-70d2-4652-910a-5d05db6a3ebc@suse.com \
--to=jbeulich@suse.com \
--cc=alistair.francis@wdc.com \
--cc=bobbyeshleman@gmail.com \
--cc=connojdavis@gmail.com \
--cc=oleksii.kurochko@gmail.com \
--cc=roger.pau@citrix.com \
--cc=sanastasio@raptorengineering.com \
--cc=xen-devel@lists.xenproject.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 read-only IMAP folder(s) and NNTP newsgroup(s).