From: Oleksii <oleksii.kurochko@gmail.com>
To: Roger Pau Monne <roger.pau@citrix.com>, xen-devel@lists.xenproject.org
Cc: Shawn Anastasio <sanastasio@raptorengineering.com>,
Alistair Francis <alistair.francis@wdc.com>,
Bob Eshleman <bobbyeshleman@gmail.com>,
Connor Davis <connojdavis@gmail.com>
Subject: Re: [PATCH for-4.19] ppc/riscv: fix arch_acquire_resource_check()
Date: Thu, 02 May 2024 10:46:12 +0200 [thread overview]
Message-ID: <2cabc6a1448c6f18cab963bc463347f088d643dd.camel@gmail.com> (raw)
In-Reply-To: <20240430153423.80875-1-roger.pau@citrix.com>
On Tue, 2024-04-30 at 17:34 +0200, 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.
>
> 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.
I am okay with such adjustment for now as it is more safe and nothing
will be missed during implementation of p2m, but I am curious how then
Arm handles that, their implementation is also just returns true. ( I
planned to have p2m implementation similar to Arm )
Anyway, based on that it safer for RISC-V:
Reviewed-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
>
> 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 8:46 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
2024-05-02 7:35 ` Roger Pau Monné
2024-05-02 8:46 ` Oleksii [this message]
2024-05-02 10:31 ` Roger Pau Monné
2024-05-05 22:12 ` Shawn Anastasio
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