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From: James Morse <james.morse@arm.com>
To: Julien Thierry <julien.thierry@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, daniel.thompson@linaro.org,
	joel@joelfernandes.org, marc.zyngier@arm.com,
	mark.rutland@arm.com, christoffer.dall@arm.com,
	catalin.marinas@arm.com, will.deacon@arm.com
Subject: Re: [PATCH v5 05/27] arm64: Use daifflag_restore after bp_hardening
Date: Wed, 12 Sep 2018 13:28:19 +0100	[thread overview]
Message-ID: <71bb5289-b381-65da-c609-fa4a08640425@arm.com> (raw)
In-Reply-To: <8f200315-1db9-1905-71ae-cb4269450b7c@arm.com>

Hi Julien,

On 12/09/18 12:11, Julien Thierry wrote:
> On 12/09/18 11:32, James Morse wrote:
>> On 28/08/18 16:51, Julien Thierry wrote:
>>> For EL0 entries requiring bp_hardening, daif status is kept at
>>> DAIF_PROCCTX_NOIRQ until after hardening has been done. Then interrupts
>>> are enabled through local_irq_enable().
>>>
>>> Before using local_irq_* functions, daifflags should be properly restored
>>> to a state where IRQs are enabled.
>>
>>> Enable IRQs by restoring DAIF_PROCCTX state after bp hardening.
>>
>> Is this just for symmetry, or are you going on to add something to the daifflags
>> state that local_irq_* functions won't change? (if so, could you allude to that
>> in the commit message)

> What happens is that once we use ICC_PMR_EL1, local_irq_enable will not touch
> PSR.I. And we are coming back from an entry where PSR.I was kept to 1 so
> local_irq_enable was not actually enabling the interrupts. On the otherhand,
> restore will affect both.

Got it. Thanks!

Does this mean stop_machine()s local_save_flags()/local_irq_restore() will not
be symmetric around __apply_alternatives_multi_stop()?
I see you add alternatives in these in patch 15, but I haven't got that far yet)


> Another option is to have the asm macro "enable_da_f" also switch to PMR usage
> (i.e. "just keep normal interrupts disabled"). Overall it would probably be
> easier to reason with, but I'm just unsure whether it is acceptable to receive a
> Pseudo NMI before having applied the bp_hardening.

Wouldn't this give the interrupt controller a headache? I assume IRQs really are
masked when handle_arch_irq is called. (I know nothing about the gic)


Thanks,

James

  reply	other threads:[~2018-09-12 12:28 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-28 15:51 [PATCH v5 00/27] arm64: provide pseudo NMI with GICv3 Julien Thierry
2018-08-28 15:51 ` [PATCH v5 01/27] arm64: cpufeature: Set SYSREG_GIC_CPUIF as a boot system feature Julien Thierry
2018-09-21 15:56   ` Marc Zyngier
     [not found]     ` <MWHPR0601MB3707D7CF3B55BF40EEEA0D52C4160@MWHPR0601MB3707.namprd06.prod.outlook.com>
2018-09-25  8:13       ` Marc Zyngier
2018-08-28 15:51 ` [PATCH v5 02/27] arm64: cpufeature: Use alternatives for VHE cpu_enable Julien Thierry
2018-09-12 10:28   ` James Morse
2018-09-12 12:03     ` Julien Thierry
2018-09-18 17:46       ` James Morse
2018-09-12 12:37     ` Suzuki K Poulose
2018-08-28 15:51 ` [PATCH v5 03/27] arm64: alternative: Apply alternatives early in boot process Julien Thierry
2018-09-12 10:29   ` James Morse
2018-09-12 16:49     ` Julien Thierry
2018-09-17 23:44       ` Daniel Thompson
2018-09-18  7:37         ` Julien Thierry
2018-09-18 17:47         ` James Morse
2018-09-21 16:05       ` Marc Zyngier
2018-08-28 15:51 ` [PATCH v5 04/27] arm64: daifflags: Use irqflags functions for daifflags Julien Thierry
2018-09-12 12:28   ` James Morse
2018-10-03 15:09   ` Catalin Marinas
2018-08-28 15:51 ` [PATCH v5 05/27] arm64: Use daifflag_restore after bp_hardening Julien Thierry
2018-09-12 10:32   ` James Morse
2018-09-12 11:11     ` Julien Thierry
2018-09-12 12:28       ` James Morse [this message]
2018-09-12 13:03         ` Julien Thierry
2018-10-03 15:12   ` Catalin Marinas
2018-08-28 15:51 ` [PATCH v5 06/27] arm64: Delay daif masking for user return Julien Thierry
2018-09-12 10:31   ` James Morse
2018-09-12 13:07     ` Julien Thierry
2018-08-28 15:51 ` [PATCH v5 07/27] arm64: xen: Use existing helper to check interrupt status Julien Thierry
2018-08-29 21:35   ` Stefano Stabellini
2018-10-03 15:14   ` Catalin Marinas
2018-08-28 15:51 ` [PATCH v5 08/27] irqchip/gic: Unify GIC priority definitions Julien Thierry
2018-10-03  9:24   ` Marc Zyngier
2018-08-28 15:51 ` [PATCH v5 09/27] irqchip/gic: Lower priority of GIC interrupts Julien Thierry
2018-08-28 15:51 ` [PATCH v5 10/27] arm64: cpufeature: Add cpufeature for IRQ priority masking Julien Thierry
2018-08-28 15:51 ` [PATCH v5 11/27] arm64: Make PMR part of task context Julien Thierry
2018-08-28 15:51 ` [PATCH v5 12/27] arm64: Unmask PMR before going idle Julien Thierry
2018-08-28 15:51 ` [PATCH v5 13/27] arm/arm64: gic-v3: Add helper functions to manage IRQ priorities Julien Thierry
2018-08-28 15:51 ` [PATCH v5 14/27] arm64: kvm: Unmask PMR before entering guest Julien Thierry
2018-08-28 15:51 ` [PATCH v5 15/27] arm64: irqflags: Use ICC_PMR_EL1 for interrupt masking Julien Thierry
2018-09-21 17:39   ` Julien Thierry
2018-09-21 17:55     ` Julien Thierry
2018-08-28 15:51 ` [PATCH v5 16/27] arm64: daifflags: Include PMR in daifflags restore operations Julien Thierry
2018-08-28 15:51 ` [PATCH v5 17/27] irqchip/gic-v3: Factor group0 detection into functions Julien Thierry
2018-08-28 15:51 ` [PATCH v5 18/27] irqchip/gic-v3: Do not overwrite PMR value Julien Thierry
2018-08-28 15:51 ` [PATCH v5 19/27] irqchip/gic-v3: Remove acknowledge loop Julien Thierry
2018-10-03  9:26   ` Marc Zyngier
2018-08-28 15:51 ` [PATCH v5 20/27] irqchip/gic-v3: Switch to PMR masking after IRQ acknowledge Julien Thierry
2018-08-28 15:51 ` [PATCH v5 21/27] arm64: Switch to PMR masking when starting CPUs Julien Thierry
2018-08-28 15:51 ` [PATCH v5 22/27] arm64: Add build option for IRQ masking via priority Julien Thierry
2018-08-28 15:51 ` [PATCH v5 23/27] arm64: Handle serror in NMI context Julien Thierry
2018-08-28 15:51 ` [PATCH v5 24/27] irqchip/gic-v3: Detect current view of GIC priorities Julien Thierry
2018-08-28 15:51 ` [PATCH v5 25/27] irqchip/gic-v3: Add base support for pseudo-NMI Julien Thierry
2018-08-28 15:51 ` [PATCH v5 26/27] irqchip/gic: Add functions to access irq priorities Julien Thierry
2018-08-28 15:51 ` [PATCH v5 27/27] irqchip/gic-v3: Allow interrupts to be set as pseudo-NMI Julien Thierry
2018-08-29 11:37 ` [PATCH v5 00/27] arm64: provide pseudo NMI with GICv3 Daniel Thompson
2018-08-29 12:58   ` Julien Thierry

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