From: Jan Beulich <jbeulich@suse.com>
To: Oleksandr Tyshchenko <olekstysh@gmail.com>
Cc: "Oleksandr Tyshchenko" <oleksandr_tyshchenko@epam.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Julien Grall" <julien@xen.org>,
"Bertrand Marquis" <bertrand.marquis@arm.com>,
"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"George Dunlap" <george.dunlap@citrix.com>,
"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>,
"Julien Grall" <jgrall@amazon.com>,
xen-devel@lists.xenproject.org, "Henry Wang" <Henry.Wang@arm.com>
Subject: Re: [PATCH V7 2/2] xen/gnttab: Store frame GFN in struct page_info on Arm
Date: Tue, 11 Oct 2022 13:59:59 +0200 [thread overview]
Message-ID: <df56f268-59d8-4b9a-52a6-40bfd0b91414@suse.com> (raw)
In-Reply-To: <20220716145658.4175730-2-olekstysh@gmail.com>
On 16.07.2022 16:56, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>
> Rework Arm implementation to store grant table frame GFN
> in struct page_info directly instead of keeping it in
> standalone status/shared arrays. This patch is based on
> the assumption that a grant table page is a xenheap page.
>
> To cover 64-bit/40-bit IPA on Arm64/Arm32 we need the space
> to hold 52-bit/28-bit + extra bit value respectively. In order
> to not grow the size of struct page_info borrow the required
> amount of bits from type_info's count portion which current
> context won't suffer (currently only 1 bit is used on Arm).
I'm afraid this isn't true: There's no requirement for a guest to pass
all different GFNs to VCPUOP_register_vcpu_info, yet map_vcpu_info()
tries to obtain a reference for every vCPU. With my adding of GFN
(really gaddr) based registration of the runstate area (already
looking towards 4.18) the maximum possible count is to further grow.
I guess this went unnoticed because Linux presumably uses different
GFNs for every vCPU, so the issue doesn't surface. But I'm afraid this
is a regression (unless I'm overlooking something, perhaps a
mitigating factor) which wants fixing for 4.17.
Jan
next prev parent reply other threads:[~2022-10-11 12:00 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-16 14:56 [PATCH V7 1/2] xen/arm: Harden the P2M code in p2m_remove_mapping() Oleksandr Tyshchenko
2022-07-16 14:56 ` [PATCH V7 2/2] xen/gnttab: Store frame GFN in struct page_info on Arm Oleksandr Tyshchenko
2022-07-16 15:08 ` Julien Grall
2022-07-16 15:20 ` Oleksandr Tyshchenko
2022-07-18 8:53 ` Jan Beulich
2022-10-11 11:59 ` Jan Beulich [this message]
2022-10-11 13:01 ` Julien Grall
2022-10-11 13:28 ` Jan Beulich
2022-10-11 13:33 ` Julien Grall
2022-10-11 13:38 ` Jan Beulich
2022-10-17 13:46 ` Jan Beulich
2022-10-17 14:37 ` Julien Grall
2022-07-16 15:06 ` [PATCH V7 1/2] xen/arm: Harden the P2M code in p2m_remove_mapping() Julien Grall
2022-07-16 15:29 ` Oleksandr Tyshchenko
2022-07-20 18:20 ` Julien Grall
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