From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Suraj Jitindar Singh <sjitindarsingh@gmail.com>,
linuxppc-dev@lists.ozlabs.org
Cc: kvm-ppc@vger.kernel.org, sjitindarsingh@gmail.com,
david@gibson.dropbear.id.au
Subject: Re: [PATCH] powerpc: mm: Limit rma_size to 1TB when running without HV mode
Date: Thu, 18 Jul 2019 23:56:39 +1000 (AEST) [thread overview]
Message-ID: <45qFzq6mgpz9sDQ@ozlabs.org> (raw)
In-Reply-To: <20190710052018.14628-1-sjitindarsingh@gmail.com>
On Wed, 2019-07-10 at 05:20:18 UTC, Suraj Jitindar Singh wrote:
> The virtual real mode addressing (VRMA) mechanism is used when a
> partition is using HPT (Hash Page Table) translation and performs
> real mode accesses (MSR[IR|DR] = 0) in non-hypervisor mode. In this
> mode effective address bits 0:23 are treated as zero (i.e. the access
> is aliased to 0) and the access is performed using an implicit 1TB SLB
> entry.
>
> The size of the RMA (Real Memory Area) is communicated to the guest as
> the size of the first memory region in the device tree. And because of
> the mechanism described above can be expected to not exceed 1TB. In the
> event that the host erroneously represents the RMA as being larger than
> 1TB, guest accesses in real mode to memory addresses above 1TB will be
> aliased down to below 1TB. This means that a memory access performed in
> real mode may differ to one performed in virtual mode for the same memory
> address, which would likely have unintended consequences.
>
> To avoid this outcome have the guest explicitly limit the size of the
> RMA to the current maximum, which is 1TB. This means that even if the
> first memory block is larger than 1TB, only the first 1TB should be
> accessed in real mode.
>
> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
> Tested-by: Satheesh Rajendran <sathnaga@linux.vnet.ibm.com>
> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/da0ef93310e67ae6902efded60b6724dab27a5d1
cheers
WARNING: multiple messages have this Message-ID (diff)
From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Suraj Jitindar Singh <sjitindarsingh@gmail.com>,
linuxppc-dev@lists.ozlabs.org
Cc: kvm-ppc@vger.kernel.org, sjitindarsingh@gmail.com,
david@gibson.dropbear.id.au
Subject: Re: [PATCH] powerpc: mm: Limit rma_size to 1TB when running without HV mode
Date: Thu, 18 Jul 2019 13:56:39 +0000 [thread overview]
Message-ID: <45qFzq6mgpz9sDQ@ozlabs.org> (raw)
In-Reply-To: <20190710052018.14628-1-sjitindarsingh@gmail.com>
In-Reply-To: <20190710052018.14628-1-sjitindarsingh@gmail.com>
On Wed, 2019-07-10 at 05:20:18 UTC, Suraj Jitindar Singh wrote:
> The virtual real mode addressing (VRMA) mechanism is used when a
> partition is using HPT (Hash Page Table) translation and performs
> real mode accesses (MSR[IR|DR] = 0) in non-hypervisor mode. In this
> mode effective address bits 0:23 are treated as zero (i.e. the access
> is aliased to 0) and the access is performed using an implicit 1TB SLB
> entry.
>
> The size of the RMA (Real Memory Area) is communicated to the guest as
> the size of the first memory region in the device tree. And because of
> the mechanism described above can be expected to not exceed 1TB. In the
> event that the host erroneously represents the RMA as being larger than
> 1TB, guest accesses in real mode to memory addresses above 1TB will be
> aliased down to below 1TB. This means that a memory access performed in
> real mode may differ to one performed in virtual mode for the same memory
> address, which would likely have unintended consequences.
>
> To avoid this outcome have the guest explicitly limit the size of the
> RMA to the current maximum, which is 1TB. This means that even if the
> first memory block is larger than 1TB, only the first 1TB should be
> accessed in real mode.
>
> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
> Tested-by: Satheesh Rajendran <sathnaga@linux.vnet.ibm.com>
> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/da0ef93310e67ae6902efded60b6724dab27a5d1
cheers
next prev parent reply other threads:[~2019-07-18 14:05 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-10 5:20 [PATCH] powerpc: mm: Limit rma_size to 1TB when running without HV mode Suraj Jitindar Singh
2019-07-10 5:20 ` Suraj Jitindar Singh
2019-07-10 7:32 ` Satheesh Rajendran
2019-07-10 7:44 ` Satheesh Rajendran
2019-07-10 14:21 ` David Gibson
2019-07-10 14:21 ` David Gibson
2019-07-12 13:09 ` Michael Ellerman
2019-07-12 13:09 ` Michael Ellerman
2019-07-15 1:58 ` Suraj Jitindar Singh
2019-07-15 1:58 ` Suraj Jitindar Singh
2019-07-15 2:23 ` Michael Ellerman
2019-07-15 2:23 ` Michael Ellerman
2019-07-18 13:56 ` Michael Ellerman [this message]
2019-07-18 13:56 ` Michael Ellerman
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