From: Catalin Marinas <catalin.marinas@arm.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: james.morse@arm.com, will@kernel.org, hch@lst.de,
linux-arm-kernel@lists.infradead.org, robin.murphy@arm.com
Subject: Re: [PATCHv4 14/17] arm64: uaccess: remove set_fs()
Date: Tue, 17 Nov 2020 10:54:18 +0000 [thread overview]
Message-ID: <X7Or2k3IKdUBrXsi@trantor> (raw)
In-Reply-To: <20201117104454.GA73209@C02TD0UTHF1T.local>
On Tue, Nov 17, 2020 at 10:44:54AM +0000, Mark Rutland wrote:
> On Mon, Nov 16, 2020 at 05:40:48PM +0000, Catalin Marinas wrote:
> > On Fri, Nov 13, 2020 at 12:49:34PM +0000, Mark Rutland wrote:
> > > We no longer need to flip UAO to access kernel memory under KERNEL_DS,
> > > and head.S unconditionally clears UAO for all kernel configurations via
> > > an ERET in init_kernel_el. Thus, we don't need to dynamically flip UAO,
> > > nor do we need to context-switch it. However, we do need to clear UAO
> > > (and set PAN) during SDEI entry.
> >
> > If the kernel never sets the UAO bit, why do we need to clear it during
> > SDEI entry?
>
> The fear was taking an SDEI event from a VM which had UAO set, with the
> SDEI FW not clearing UAO.
>
> That might not happen in practice because while the spec implies that
> could happen, TF-A currently generates a new PSTATE from scratch, and
> going forward the spec will be aligned with regular exception entry
> rules for PSTATE (so UAO will be cleared automatically).
Does this requirement apply retrospectively or it only for the future
SDEI specs?
> So we can probably drop the clearing of UAO if you prefer.
I don't like clearing UAO specifically. There may be other PSTATE bits
in the future we don't know or care about and that are left set by
firmware. If we don't trust firmware to give a clean PSTATE, can we
reset it with an ERET?
--
Catalin
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next prev parent reply other threads:[~2020-11-17 10:55 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-13 12:49 [PATCHv4 00/17] arm64: remove set_fs() and friends Mark Rutland
2020-11-13 12:49 ` [PATCHv4 01/17] arm64: ensure ERET from kthread is illegal Mark Rutland
2020-11-13 12:49 ` [PATCHv4 02/17] arm64: add C wrappers for SET_PSTATE_*() Mark Rutland
2020-11-13 12:49 ` [PATCHv4 03/17] arm64: head.S: rename el2_setup -> init_kernel_el Mark Rutland
2020-11-13 12:49 ` [PATCHv4 04/17] arm64: head.S: cleanup SCTLR_ELx initialization Mark Rutland
2020-11-13 12:49 ` [PATCHv4 05/17] arm64: head.S: always initialize PSTATE Mark Rutland
2020-11-13 12:49 ` [PATCHv4 06/17] arm64: sdei: move uaccess logic to arch/arm64/ Mark Rutland
2020-11-16 17:42 ` Catalin Marinas
2020-11-26 18:42 ` James Morse
2020-11-13 12:49 ` [PATCHv4 07/17] arm64: sdei: explicitly simulate PAN/UAO entry Mark Rutland
2020-11-26 18:42 ` James Morse
2020-12-01 12:14 ` Mark Rutland
2020-11-13 12:49 ` [PATCHv4 08/17] arm64: uaccess: move uao_* alternatives to asm-uaccess.h Mark Rutland
2020-11-14 9:22 ` Christoph Hellwig
2020-11-16 12:25 ` Mark Rutland
2020-11-13 12:49 ` [PATCHv4 09/17] arm64: uaccess: rename privileged uaccess routines Mark Rutland
2020-11-13 12:49 ` [PATCHv4 10/17] arm64: uaccess: simplify __copy_user_flushcache() Mark Rutland
2020-11-13 12:49 ` [PATCHv4 11/17] arm64: uaccess: refactor __{get,put}_user Mark Rutland
2020-11-13 12:49 ` [PATCHv4 12/17] arm64: uaccess: split user/kernel routines Mark Rutland
2020-11-26 18:42 ` James Morse
2020-12-01 11:03 ` Mark Rutland
2020-12-02 12:19 ` Mark Rutland
2020-11-13 12:49 ` [PATCHv4 13/17] arm64: uaccess cleanup macro naming Mark Rutland
2020-11-13 12:49 ` [PATCHv4 14/17] arm64: uaccess: remove set_fs() Mark Rutland
2020-11-16 17:40 ` Catalin Marinas
2020-11-17 10:44 ` Mark Rutland
2020-11-17 10:54 ` Catalin Marinas [this message]
2020-11-17 10:57 ` Mark Rutland
2020-11-17 11:02 ` Catalin Marinas
2020-11-17 11:07 ` Mark Rutland
2020-11-17 11:10 ` Catalin Marinas
2020-11-26 18:42 ` James Morse
2020-11-26 18:42 ` James Morse
2020-12-01 12:30 ` Mark Rutland
2020-11-13 12:49 ` [PATCHv4 15/17] arm64: uaccess: remove addr_limit_user_check() Mark Rutland
2020-11-13 12:49 ` [PATCHv4 16/17] arm64: uaccess: remove redundant PAN toggling Mark Rutland
2020-11-13 12:49 ` [PATCHv4 17/17] arm64: uaccess: remove vestigal UAO support Mark Rutland
2020-11-25 19:10 ` [PATCHv4 00/17] arm64: remove set_fs() and friends Catalin Marinas
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