linux-kernel - Re: [PATCH v3 2/3] arch/arm64: fpsimd: Introduce fpsimd_save_and_flush_cpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190425141230.GE3567@e103592.cambridge.arm.com>
Date:   Thu, 25 Apr 2019 15:12:31 +0100
From:   Dave Martin <Dave.Martin@....com>
To:     Julien Grall <julien.grall@....com>
Cc:     julien.thierry@....com, marc.zyngier@....com,
        catalin.marinas@....com, ard.biesheuvel@...aro.org,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        christoffer.dall@....com, james.morse@....com,
        suzuki.poulose@....com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 2/3] arch/arm64: fpsimd: Introduce
 fpsimd_save_and_flush_cpu_state() and use it

On Thu, Apr 25, 2019 at 01:37:40PM +0100, Julien Grall wrote:
> Hi Dave,
> 
> On 24/04/2019 14:17, Dave Martin wrote:
> >On Tue, Apr 23, 2019 at 02:57:18PM +0100, Julien Grall wrote:
> >>tent-Length: 4295
> >>Lines: 128
> >>
> >>The only external user of fpsimd_save() and fpsimd_flush_cpu_state() is
> >>the KVM FPSIMD code.
> >>
> >>A following patch will introduce a mechanism to acquire owernship of the
> >>FPSIMD/SVE context for performing context management operations. Rather
> >>than having to export the new helpers to get/put the context, we can just
> >>introduce a new function to combine fpsimd_save() and
> >>fpsimd_flush_cpu_state().
> >>
> >>This has also the advantage to remove any external call of fpsimd_save()
> >>and fpsimd_flush_cpu_state(), so they can be turned static.
> >>
> >>Lastly, the new function can also be used in the PM notifier.
> >>
> >>Signed-off-by: Julien Grall <julien.grall@....com>
> >>
> >>---
> >>     kernel_neon_begin() does not use fpsimd_save_and_flush_cpu_state()
> >>     because the next patch will modify the function to also grab the
> >>     FPSIMD/SVE context.
> >>
> >>     Changes in v3:
> >>         - Rework the commit message
> >>         - Move the prototype of fpsimd_save_and_flush_cpu_state()
> >>         further down in the header
> >>         - Remove comment in kvm_arch_vcpu_put_fp()
> >>
> >>     Changes in v2:
> >>         - Patch added
> >>---
> >>  arch/arm64/include/asm/fpsimd.h |  5 ++---
> >>  arch/arm64/kernel/fpsimd.c      | 17 +++++++++++++----
> >>  arch/arm64/kvm/fpsimd.c         |  4 +---
> >>  3 files changed, 16 insertions(+), 10 deletions(-)
> >>
> >>diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
> >>index b73d12fcc7f9..c311d36ecffe 100644
> >>--- a/arch/arm64/include/asm/fpsimd.h
> >>+++ b/arch/arm64/include/asm/fpsimd.h
> >>@@ -48,8 +48,6 @@ struct task_struct;
> >>  extern void fpsimd_save_state(struct user_fpsimd_state *state);
> >>  extern void fpsimd_load_state(struct user_fpsimd_state *state);
> >>-extern void fpsimd_save(void);
> >>-
> >>  extern void fpsimd_thread_switch(struct task_struct *next);
> >>  extern void fpsimd_flush_thread(void);
> >>@@ -63,7 +61,8 @@ extern void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *state,
> >>  				     void *sve_state, unsigned int sve_vl);
> >>  extern void fpsimd_flush_task_state(struct task_struct *target);
> >>-extern void fpsimd_flush_cpu_state(void);
> >>+
> >>+extern void fpsimd_save_and_flush_cpu_state(void);
> >
> >Nit: You could drop this blank line: these are all "state maintenance"
> >operations, roughly speaking.
> >
> >But don't bother unless you respin for some other reason.
> 
> It looks like I will need to make some changes in patch #3. So I will remove
> the line at the same time.

OK, fair enough.

Cheers
---Dave