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From: Andrea Parri <parri.andrea@gmail.com>
To: Palmer Dabbelt <palmer@dabbelt.com>
Cc: mathieu.desnoyers@efficios.com, paulmck@kernel.org,
	Paul Walmsley <paul.walmsley@sifive.com>,
	aou@eecs.berkeley.edu, mmaas@google.com, hboehm@google.com,
	striker@us.ibm.com, charlie@rivosinc.com, rehn@rivosinc.com,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] membarrier: riscv: Provide core serializing command
Date: Wed, 6 Dec 2023 18:42:44 +0100	[thread overview]
Message-ID: <ZXCylOEXSbEMGB96@andrea> (raw)
In-Reply-To: <mhng-26a1b3dd-ca9e-4b82-86e9-1faf1e3571e5@palmer-ri-x1c9>

> > The final version of this fix will likely depend on some machinery/code
> > introduced by 3ccfebedd8cf54 ("powerpc, membarrier: Skip memory barrier
> > in switch_mm()"); but, yes, nothing we can't safely adjust I think.
> 
> Ya, I guess we'll have to look to know for sure but hopefully it's
> manageable.

Absolutely.  One approach would be to follow what PowerPC did: AFAIU, before
3ccfebedd8cf54 membarrier/powerpc used to hard code the required barrier in
in finish_task_switch(), "masking" it as an smp_mb__after_unlock_lock(); riscv
could use a similar approach (though with a different/new mask function).
Alternatively, we could maybe keep the barrier in switch_mm().

But let me complete and send out v2 with the fix at stake...  this should give
us a more concrete basis to discuss about these matters.

  Andrea

WARNING: multiple messages have this Message-ID (diff)
From: Andrea Parri <parri.andrea@gmail.com>
To: Palmer Dabbelt <palmer@dabbelt.com>
Cc: mathieu.desnoyers@efficios.com, paulmck@kernel.org,
	Paul Walmsley <paul.walmsley@sifive.com>,
	aou@eecs.berkeley.edu, mmaas@google.com, hboehm@google.com,
	striker@us.ibm.com, charlie@rivosinc.com, rehn@rivosinc.com,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] membarrier: riscv: Provide core serializing command
Date: Wed, 6 Dec 2023 18:42:44 +0100	[thread overview]
Message-ID: <ZXCylOEXSbEMGB96@andrea> (raw)
In-Reply-To: <mhng-26a1b3dd-ca9e-4b82-86e9-1faf1e3571e5@palmer-ri-x1c9>

> > The final version of this fix will likely depend on some machinery/code
> > introduced by 3ccfebedd8cf54 ("powerpc, membarrier: Skip memory barrier
> > in switch_mm()"); but, yes, nothing we can't safely adjust I think.
> 
> Ya, I guess we'll have to look to know for sure but hopefully it's
> manageable.

Absolutely.  One approach would be to follow what PowerPC did: AFAIU, before
3ccfebedd8cf54 membarrier/powerpc used to hard code the required barrier in
in finish_task_switch(), "masking" it as an smp_mb__after_unlock_lock(); riscv
could use a similar approach (though with a different/new mask function).
Alternatively, we could maybe keep the barrier in switch_mm().

But let me complete and send out v2 with the fix at stake...  this should give
us a more concrete basis to discuss about these matters.

  Andrea

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

  reply	other threads:[~2023-12-06 17:42 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-11-27 10:32 [PATCH 0/2] membarrier: riscv: Provide core serializing command Andrea Parri
2023-11-27 10:32 ` Andrea Parri
2023-11-27 10:32 ` [PATCH 1/2] locking: Introduce prepare_sync_core_cmd() Andrea Parri
2023-11-27 10:32   ` Andrea Parri
2023-11-27 12:53   ` Mathieu Desnoyers
2023-11-27 12:53     ` Mathieu Desnoyers
2023-11-27 10:32 ` [PATCH 2/2] membarrier: riscv: Provide core serializing command Andrea Parri
2023-11-27 10:32   ` Andrea Parri
2023-11-27 13:28   ` Mathieu Desnoyers
2023-11-27 13:28     ` Mathieu Desnoyers
2023-11-28 15:13     ` Andrea Parri
2023-11-28 15:13       ` Andrea Parri
2023-11-28 18:39       ` Mathieu Desnoyers
2023-11-28 18:39         ` Mathieu Desnoyers
2023-11-29 18:29         ` Andrea Parri
2023-11-29 18:29           ` Andrea Parri
2023-11-29 20:00           ` Mathieu Desnoyers
2023-11-29 20:00             ` Mathieu Desnoyers
2023-11-29 21:25             ` Andrea Parri
2023-11-29 21:25               ` Andrea Parri
2023-11-29 21:32               ` Mathieu Desnoyers
2023-11-29 21:32                 ` Mathieu Desnoyers
2023-11-29 22:43                 ` Andrea Parri
2023-11-29 22:43                   ` Andrea Parri
2023-12-06 13:05                   ` Palmer Dabbelt
2023-12-06 13:05                     ` Palmer Dabbelt
2023-12-06 14:11                     ` Andrea Parri
2023-12-06 14:11                       ` Andrea Parri
2023-12-06 14:15                       ` Palmer Dabbelt
2023-12-06 14:15                         ` Palmer Dabbelt
2023-12-06 17:42                         ` Andrea Parri [this message]
2023-12-06 17:42                           ` Andrea Parri
2023-12-06 17:56                           ` Palmer Dabbelt
2023-12-06 17:56                             ` Palmer Dabbelt

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