Xen-Devel Archive on lore.kernel.org
 help / color / Atom feed
From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Chao Gao <chao.gao@intel.com>
Cc: xen-devel@lists.xenproject.org, Jan Beulich <jbeulich@suse.com>,
	Ashok Raj <ashok.raj@intel.com>, Wei Liu <wl@xen.org>,
	Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [Xen-devel] [PATCH v9 12/15] microcode: reduce memory allocation and copy when creating a patch
Date: Mon, 26 Aug 2019 10:11:03 +0200
Message-ID: <20190826081103.hb5diw7brmnbiwbv@Air-de-Roger> (raw)
In-Reply-To: <20190826070320.GA11910@gao-cwp>

On Mon, Aug 26, 2019 at 03:03:22PM +0800, Chao Gao wrote:
> On Fri, Aug 23, 2019 at 10:11:21AM +0200, Roger Pau Monné wrote:
> >On Mon, Aug 19, 2019 at 09:25:25AM +0800, Chao Gao wrote:
> >> To create a microcode patch from a vendor-specific update,
> >> allocate_microcode_patch() copied everything from the update.
> >> It is not efficient. Essentially, we just need to go through
> >> ucodes in the blob, find the one with the newest revision and
> >> install it into the microcode_patch. In the process, buffers
> >> like mc_amd, equiv_cpu_table (on AMD side), and mc (on Intel
> >> side) can be reused. microcode_patch now is allocated after
> >> it is sure that there is a matching ucode.
> >
> >Oh, I think this answers my question on a previous patch.
> >
> >For future series it would be nice to avoid so many rewrites in the
> >same series, alloc_microcode_patch is already modified in a previous
> >patch, just to be removed here. It also makes it harder to follow
> >what's going on.
> 
> Got it. This patch is added in this new version. And some trivial
> patches already got reviewed-by. So I don't merge it with them.
> 
> >>      while ( (error = get_ucode_from_buffer_amd(mc_amd, buf, bufsize,
> >>                                                 &offset)) == 0 )
> >>      {
> >> -        struct microcode_patch *new_patch = alloc_microcode_patch(mc_amd);
> >> -
> >> -        if ( IS_ERR(new_patch) )
> >> -        {
> >> -            error = PTR_ERR(new_patch);
> >> -            break;
> >> -        }
> >> -
> >>          /*
> >> -         * If the new patch covers current CPU, compare patches and store the
> >> +         * If the new ucode covers current CPU, compare ucodes and store the
> >>           * one with higher revision.
> >>           */
> >> -        if ( (microcode_fits(new_patch->mc_amd) != MIS_UCODE) &&
> >> -             (!patch || (compare_patch(new_patch, patch) == NEW_UCODE)) )
> >> +#define REV_ID(mpb) (((struct microcode_header_amd *)(mpb))->processor_rev_id)
> >> +        if ( (microcode_fits(mc_amd) != MIS_UCODE) &&
> >> +             (!saved || (REV_ID(mc_amd->mpb) > REV_ID(saved))) )
> >> +#undef REV_ID
> >>          {
> >> -            struct microcode_patch *tmp = patch;
> >> -
> >> -            patch = new_patch;
> >> -            new_patch = tmp;
> >> +            xfree(saved);
> >> +            saved = mc_amd->mpb;
> >> +            saved_size = mc_amd->mpb_size;
> >>          }
> >> -
> >> -        if ( new_patch )
> >> -            microcode_free_patch(new_patch);
> >> +        else
> >> +            xfree(mc_amd->mpb);
> 
> It might be better to move 'mc_amd->mpb = NULL' here.
> 
> >>  
> >>          if ( offset >= bufsize )
> >>              break;
> >> @@ -593,9 +548,25 @@ static struct microcode_patch *cpu_request_microcode(const void *buf,
> >>               *(const uint32_t *)(buf + offset) == UCODE_MAGIC )
> >>              break;
> >>      }
> >> -    xfree(mc_amd->mpb);
> >> -    xfree(mc_amd->equiv_cpu_table);
> >> -    xfree(mc_amd);
> >> +
> >> +    if ( saved )
> >> +    {
> >> +        mc_amd->mpb = saved;
> >> +        mc_amd->mpb_size = saved_size;
> >> +        patch = xmalloc(struct microcode_patch);
> >> +        if ( patch )
> >> +            patch->mc_amd = mc_amd;
> >> +        else
> >> +        {
> >> +            free_patch(mc_amd);
> >> +            error = -ENOMEM;
> >> +        }
> >> +    }
> >> +    else
> >> +    {
> >> +        mc_amd->mpb = NULL;
> >
> >What's the point in setting mpb to NULL if you are just going to free
> >mc_amd below?
> 
> To avoid double free here. mc_amd->mpb is always freed or saved.
> And here we want to free mc_amd itself and mc_amd->equiv_cpu_table.

But there's no chance of a double free here, since you are freeing
mc_amd in the line below after setting mpb = NULL.

I think it would make sense to set mpb = NULL after freeing it inside
the loop.

With that you can add my:

Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

> >
> >Also, I'm not sure I understand why you need to free mc_amd, isn't
> >this buff memory that should be freed by the caller?
> 
> But mc_amd is allocated in this function.
> 
> >
> >ie: in the Intel counterpart below you don't seem to free the mc
> >cursor used for the get_next_ucode_from_buffer loop.
> 
> 'mc' is saved if it is newer than current patch stored in 'saved'.
> Otherwise 'mc' is freed immediately. So we don't need to free it
> again after the while loop.

Ack, thanks!

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

  reply index

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-19  1:25 [Xen-devel] [PATCH v9 00/15] improve late microcode loading Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 01/15] microcode/intel: extend microcode_update_match() Chao Gao
2019-08-28 15:12   ` Jan Beulich
2019-08-29  7:15     ` Chao Gao
2019-08-29  7:14       ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 02/15] microcode/amd: fix memory leak Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 03/15] microcode/amd: distinguish old and mismatched ucode in microcode_fits() Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 04/15] microcode: introduce a global cache of ucode patch Chao Gao
2019-08-22 11:11   ` Roger Pau Monné
2019-08-28 15:21   ` Jan Beulich
2019-08-29 10:18   ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 05/15] microcode: clean up microcode_resume_cpu Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 06/15] microcode: remove struct ucode_cpu_info Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 07/15] microcode: remove pointless 'cpu' parameter Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 08/15] microcode/amd: call svm_host_osvw_init() in common code Chao Gao
2019-08-22 13:08   ` Roger Pau Monné
2019-08-28 15:26   ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 09/15] microcode: pass a patch pointer to apply_microcode() Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 10/15] microcode: split out apply_microcode() from cpu_request_microcode() Chao Gao
2019-08-22 13:59   ` Roger Pau Monné
2019-08-29 10:06     ` Jan Beulich
2019-08-30  3:22       ` Chao Gao
2019-08-30  7:25         ` Jan Beulich
2019-08-29 10:19   ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 11/15] microcode: unify loading update during CPU resuming and AP wakeup Chao Gao
2019-08-22 14:10   ` Roger Pau Monné
2019-08-22 16:44     ` Chao Gao
2019-08-23  9:09       ` Roger Pau Monné
2019-08-29  7:37         ` Chao Gao
2019-08-29  8:16           ` Roger Pau Monné
2019-08-29 10:26           ` Jan Beulich
2019-08-29 10:29   ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 12/15] microcode: reduce memory allocation and copy when creating a patch Chao Gao
2019-08-23  8:11   ` Roger Pau Monné
2019-08-26  7:03     ` Chao Gao
2019-08-26  8:11       ` Roger Pau Monné [this message]
2019-08-29 10:47   ` Jan Beulich
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 13/15] x86/microcode: Synchronize late microcode loading Chao Gao
2019-08-19 10:27   ` Sergey Dyasli
2019-08-19 14:49     ` Chao Gao
2019-08-29 12:06   ` Jan Beulich
2019-08-30  3:30     ` Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 14/15] microcode: remove microcode_update_lock Chao Gao
2019-08-19  1:25 ` [Xen-devel] [PATCH v9 15/15] microcode: block #NMI handling when loading an ucode Chao Gao
2019-08-23  8:46   ` Sergey Dyasli
2019-08-26  8:07     ` Chao Gao
2019-08-27  4:52       ` Chao Gao
2019-08-28  8:52         ` Sergey Dyasli
2019-08-29 12:11         ` Jan Beulich
2019-08-30  6:35           ` Chao Gao
2019-09-09  5:52             ` Chao Gao
2019-09-09  6:16               ` Jan Beulich
2019-08-29 12:22   ` Jan Beulich
2019-08-30  6:33     ` Chao Gao
2019-08-30  7:30       ` Jan Beulich
2019-08-22  7:51 ` [Xen-devel] [PATCH v9 00/15] improve late microcode loading Sergey Dyasli
2019-08-22 15:39   ` Chao Gao

Reply instructions:

You may reply publically 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=20190826081103.hb5diw7brmnbiwbv@Air-de-Roger \
    --to=roger.pau@citrix.com \
    --cc=andrew.cooper3@citrix.com \
    --cc=ashok.raj@intel.com \
    --cc=chao.gao@intel.com \
    --cc=jbeulich@suse.com \
    --cc=wl@xen.org \
    --cc=xen-devel@lists.xenproject.org \
    /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

Xen-Devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/xen-devel/0 xen-devel/git/0.git
	git clone --mirror https://lore.kernel.org/xen-devel/1 xen-devel/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 xen-devel xen-devel/ https://lore.kernel.org/xen-devel \
		xen-devel@lists.xenproject.org xen-devel@lists.xen.org xen-devel@archiver.kernel.org
	public-inbox-index xen-devel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.xenproject.lists.xen-devel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox