linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Andy Lutomirski <luto@kernel.org>
To: Ira Weiny <ira.weiny@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Fenghua Yu <fenghua.yu@intel.com>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	Linux-MM <linux-mm@kvack.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Greg KH <gregkh@linuxfoundation.org>
Subject: Re: [PATCH V3.1] entry: Pass irqentry_state_t by reference
Date: Tue, 15 Dec 2020 18:09:02 -0800	[thread overview]
Message-ID: <CALCETrWoh5BYnU16adT7i6tsQ77PGaLN_qyZnCy-WfO3UJoykw@mail.gmail.com> (raw)
In-Reply-To: <20201216013202.GY1563847@iweiny-DESK2.sc.intel.com>

On Tue, Dec 15, 2020 at 5:32 PM Ira Weiny <ira.weiny@intel.com> wrote:
>
> On Fri, Dec 11, 2020 at 02:14:28PM -0800, Andy Lutomirski wrote:
> > On Mon, Nov 23, 2020 at 10:10 PM <ira.weiny@intel.com> wrote:

> > IOW we have:
> >
> > struct extended_pt_regs {
> >   bool rcu_whatever;
> >   other generic fields here;
> >   struct arch_extended_pt_regs arch_regs;
> >   struct pt_regs regs;
> > };
> >
> > and arch_extended_pt_regs has unsigned long pks;
> >
> > and instead of passing a pointer to irqentry_state_t to the generic
> > entry/exit code, we just pass a pt_regs pointer.  And we have a little
> > accessor like:
> >
> > struct extended_pt_regs *extended_regs(struct pt_regs *) { return
> > container_of(...); }
> >
> > And we tell eBPF that extended_pt_regs is NOT ABI, and we will change
> > it whenever we feel like just to keep you on your toes, thank you very
> > much.
> >
> > Does this seem reasonable?
>
> Conceptually yes.  But I'm failing to see how this implementation can be made
> generic for the generic fields.  The pks fields, assuming they stay x86
> specific, would be reasonable to add in PUSH_AND_CLEAR_REGS.  But the
> rcu/lockdep field is generic.  Wouldn't we have to modify every architecture to
> add space for the rcu/lockdep bool?
>
> If not, where is a generic place that could be done?  Basically I'm missing how
> the effective stack structure can look like this:
>
> > struct extended_pt_regs {
> >   bool rcu_whatever;
> >   other generic fields here;
> >   struct arch_extended_pt_regs arch_regs;
> >   struct pt_regs regs;
> > };
>
> It seems more reasonable to make it look like:
>
> #ifdef CONFIG_ARCH_HAS_SUPERVISOR_PKEYS
> struct extended_pt_regs {
>         unsigned long pkrs;
>         struct pt_regs regs;
> };
> #endif
>
> And leave the rcu/lockdep bool passed by value as before (still in C).

We could certainly do this, but we could also allocate some generic
space.  PUSH_AND_CLEAR_REGS would get an extra instruction like:

subq %rsp, $GENERIC_PTREGS_SIZE

or however this should be written.  That field would be defined in
asm-offsets.c.  And yes, all the generic-entry architectures would
need to get onboard.

If we wanted to be fancy, we could split the generic area into
initialize-to-zero and uninitialized for debugging purposes, but that
might be more complication than is worthwhile.

  reply	other threads:[~2020-12-16  2:10 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-06 23:28 [PATCH V3 00/10] PKS: Add Protection Keys Supervisor (PKS) support V3 ira.weiny
2020-11-06 23:28 ` [PATCH V3 01/10] x86/pkeys: Create pkeys_common.h ira.weiny
2020-11-06 23:29 ` [PATCH V3 02/10] x86/fpu: Refactor arch_set_user_pkey_access() for PKS support ira.weiny
2020-11-06 23:29 ` [PATCH V3 03/10] x86/pks: Add PKS defines and Kconfig options ira.weiny
2020-11-06 23:29 ` [PATCH V3 04/10] x86/pks: Preserve the PKRS MSR on context switch ira.weiny
2020-12-17 14:50   ` Thomas Gleixner
2020-12-17 22:43     ` Thomas Gleixner
2020-12-18 13:57       ` Thomas Gleixner
2020-12-18 19:20         ` Dan Williams
2020-12-18 21:06           ` Thomas Gleixner
2020-12-18 21:58             ` Dan Williams
2020-12-18 22:44               ` Thomas Gleixner
2020-12-18 19:42         ` Ira Weiny
2020-12-18 20:10           ` Dave Hansen
2020-12-18 21:30           ` Thomas Gleixner
2020-12-18  4:05     ` Ira Weiny
2020-12-17 20:41   ` [NEEDS-REVIEW] " Dave Hansen
2020-12-18  4:10     ` Ira Weiny
2020-12-18 15:33       ` Dave Hansen
2020-11-06 23:29 ` [PATCH V3 05/10] x86/entry: Pass irqentry_state_t by reference ira.weiny
2020-11-15 18:58   ` Thomas Gleixner
2020-11-16 18:49     ` Ira Weiny
2020-11-16 20:36       ` Thomas Gleixner
2020-11-24  6:09   ` [PATCH V3.1] entry: " ira.weiny
2020-12-11 22:14     ` Andy Lutomirski
2020-12-16  1:32       ` Ira Weiny
2020-12-16  2:09         ` Andy Lutomirski [this message]
2020-12-17  0:38           ` Ira Weiny
2020-12-17 13:07       ` Thomas Gleixner
2020-12-17 13:19         ` Peter Zijlstra
2020-12-17 15:35           ` Andy Lutomirski
2020-12-17 16:58     ` Thomas Gleixner
2020-11-06 23:29 ` [PATCH V3 06/10] x86/entry: Preserve PKRS MSR across exceptions ira.weiny
2020-12-17 15:28   ` Thomas Gleixner
2020-11-06 23:29 ` [PATCH V3 07/10] x86/fault: Report the PKRS state on fault ira.weiny
2020-11-06 23:29 ` [PATCH V3 08/10] x86/pks: Add PKS kernel API ira.weiny
2020-12-23 20:39   ` Randy Dunlap
2020-11-06 23:29 ` [PATCH V3 09/10] x86/pks: Enable Protection Keys Supervisor (PKS) ira.weiny
2020-11-06 23:29 ` [PATCH V3 10/10] x86/pks: Add PKS test code ira.weiny
2020-12-17 20:55   ` Dave Hansen
2020-12-18  4:05     ` Ira Weiny
2020-12-18 16:59       ` Dan Williams
2020-12-07 22:14 ` [PATCH V3 00/10] PKS: Add Protection Keys Supervisor (PKS) support V3 Ira Weiny
2020-12-08 15:55   ` Thomas Gleixner
2020-12-08 17:22     ` Ira Weiny

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CALCETrWoh5BYnU16adT7i6tsQ77PGaLN_qyZnCy-WfO3UJoykw@mail.gmail.com \
    --to=luto@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=bp@alien8.de \
    --cc=dan.j.williams@intel.com \
    --cc=dave.hansen@linux.intel.com \
    --cc=fenghua.yu@intel.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=ira.weiny@intel.com \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-kselftest@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-nvdimm@lists.01.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH V3.1] entry: Pass irqentry_state_t by reference' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).