From: Marc Zyngier <marc.zyngier@arm.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
kvmarm@lists.cs.columbia.edu,
Christoffer Dall <christoffer.dall@linaro.org>,
Mark Rutland <mark.rutland@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
James Morse <james.morse@arm.com>
Subject: Re: [PATCH 04/18] arm64: alternatives: Enforce alignment of struct alt_instr
Date: Wed, 6 Dec 2017 14:57:29 +0000 [thread overview]
Message-ID: <dd8995ce-3065-3aba-2d93-9ed91de5cd50@arm.com> (raw)
In-Reply-To: <20171206144847.GA28074@char.us.oracle.com>
On 06/12/17 14:48, Konrad Rzeszutek Wilk wrote:
> On Wed, Dec 06, 2017 at 02:38:25PM +0000, Marc Zyngier wrote:
>> We're playing a dangerous game with struct alt_instr, as we produce
>> it using assembly tricks, but parse them using the C structure.
>> We just assume that the respective alignments of the two will
>> be the same.
>>
>> But as we add more fields to this structure, the alignment requirements
>> of the structure may change, and lead to all kind of funky bugs.
>>
>> TO solve this, let's move the definition of struct alt_instr to its
>> own file, and use this to generate the alignment constraint from
>> asm-offsets.c. The various macros are then patched to take the
>> alignment into account.
>
> Would it be better to use .p2align as on 32-bit ARM you must
> have it 4-byte aligned. Or at least have and BUILD_BUG_ON
> to make sure the size can be divided by four??
>
> Oh wait. You are not even touching ARM-32, how come? The alternative
> code can run on ARM-32 ...
How? Given that I haven't written yet, I'd be grateful if you could
share your time machine...
Thanks,
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2017-12-06 14:57 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-06 14:38 [PATCH 00/18] KVM/arm64: Randomise EL2 mappings Marc Zyngier
2017-12-06 14:38 ` [PATCH 01/18] arm64: asm-offsets: Avoid clashing DMA definitions Marc Zyngier
2017-12-06 14:38 ` [PATCH 02/18] arm64: asm-offsets: Remove unused definitions Marc Zyngier
2017-12-06 14:38 ` [PATCH 03/18] arm64: asm-offsets: Remove potential circular dependency Marc Zyngier
2017-12-06 14:38 ` [PATCH 04/18] arm64: alternatives: Enforce alignment of struct alt_instr Marc Zyngier
2017-12-06 14:48 ` Konrad Rzeszutek Wilk
2017-12-06 14:57 ` Marc Zyngier [this message]
2017-12-06 15:18 ` Konrad Rzeszutek Wilk
2017-12-06 15:39 ` Marc Zyngier
2017-12-06 14:38 ` [PATCH 05/18] arm64: alternatives: Add dynamic patching feature Marc Zyngier
2017-12-06 14:38 ` [PATCH 06/18] arm64: insn: Add N immediate encoding Marc Zyngier
2017-12-06 14:38 ` [PATCH 07/18] arm64: insn: Add encoder for bitwise operations using litterals Marc Zyngier
2017-12-06 14:38 ` [PATCH 08/18] arm64: KVM: Dynamically patch the kernel/hyp VA mask Marc Zyngier
2017-12-06 14:38 ` [PATCH 09/18] arm64: cpufeatures: Drop the ARM64_HYP_OFFSET_LOW feature flag Marc Zyngier
2017-12-06 14:38 ` [PATCH 10/18] arm64; insn: Add encoder for the EXTR instruction Marc Zyngier
2017-12-06 14:38 ` [PATCH 11/18] arm64: insn: Allow ADD/SUB (immediate) with LSL #12 Marc Zyngier
2017-12-06 14:38 ` [PATCH 12/18] arm64: KVM: Introduce EL2 VA randomisation Marc Zyngier
2017-12-06 14:38 ` [PATCH 13/18] arm64: Update the KVM memory map documentation Marc Zyngier
2017-12-06 14:38 ` [PATCH 14/18] KVM: arm/arm64: Do not use kern_hyp_va() with kvm_vgic_global_state Marc Zyngier
2017-12-06 14:38 ` [PATCH 15/18] KVM: arm/arm64: Demote HYP VA range display to being a debug feature Marc Zyngier
2017-12-06 14:38 ` [PATCH 16/18] KVM: arm/arm64: Move ioremap calls to create_hyp_io_mappings Marc Zyngier
2017-12-06 14:38 ` [PATCH 17/18] KVM: arm/arm64: Keep GICv2 HYP VAs in kvm_vgic_global_state Marc Zyngier
2017-12-06 14:38 ` [PATCH 18/18] KVM: arm/arm64: Move HYP IO VAs to the "idmap" range Marc Zyngier
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