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Date: Thu, 21 May 2015 07:01:34 +0000
From: "Wu, Feng" <feng.wu@...el.com>
To: Thomas Gleixner <tglx@...utronix.de>
CC: "joro@...tes.org" <joro@...tes.org>,
"dwmw2@...radead.org" <dwmw2@...radead.org>,
"jiang.liu@...ux.intel.com" <jiang.liu@...ux.intel.com>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Wu, Feng" <feng.wu@...el.com>
Subject: RE: [v5 3/9] iommu, x86: Abstract modify_irte() to accept two
format of irte
> -----Original Message-----
> From: Thomas Gleixner [mailto:tglx@...utronix.de]
> Sent: Wednesday, May 20, 2015 7:46 PM
> To: Wu, Feng
> Cc: joro@...tes.org; dwmw2@...radead.org; jiang.liu@...ux.intel.com;
> iommu@...ts.linux-foundation.org; linux-kernel@...r.kernel.org
> Subject: Re: [v5 3/9] iommu, x86: Abstract modify_irte() to accept two format
> of irte
>
> On Wed, 20 May 2015, Feng Wu wrote:
>
> > After introducing VT-d posted-interrupts, we have two format
> > of IRTE: remapped and posted. This patch make modify_irte()
> > suitable for both of them.
>
> > static int modify_irte(struct irq_2_iommu *irq_iommu,
> > - struct irte *irte_modified)
> > + void *data)
>
> That's hardly an abstraction. You just make the pointer void so you
> can hand in arbitrary nonsense.
>
> And with the new struct you having crap like this:
>
> + memcpy(irte_pi, &ir_data->irte_entry, sizeof(struct irte));
>
> and this:
>
> + struct irte_pi *irte_pi = (struct irte_pi *)irte;
>
> Why not extending struct irte proper and avoid the whole void pointer
> and mempcy and other crappola.
>
> Patch below.
>
> Thanks,
>
> tglx
>
> ------------->
>
> iommu: dmar: Extend struct irte for VT-d Posted-Interrrupts
>
> The IRTE (Interrupt Remapping Table Entry) is either an entry for
> remapped or for posted interrupts. The hardware distiguishes between
> remapped and posted entries by bit 15 in the low 64 bit of the
> IRTE. If cleared the entry is remapped, if set it's posted.
>
> The entries have common fields and dependent on the posted bit fields
> with different meanings.
>
> Extend struct irte to handle the differences between remap and posted
> mode by having three structs in the unions:
>
> - Shared
> - Remapped
> - Posted
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
> include/linux/dmar.h | 68
> +++++++++++++++++++++++++++++++++++++++------------
> 1 file changed, 53 insertions(+), 15 deletions(-)
>
> Index: linux/include/linux/dmar.h
> ================================================================
> ===
> --- linux.orig/include/linux/dmar.h
> +++ linux/include/linux/dmar.h
> @@ -185,28 +185,66 @@ static inline int dmar_device_remove(voi
>
> struct irte {
> union {
> + /* Shared between remap and posted mode*/
> struct {
> - __u64 present : 1,
> - fpd : 1,
> - dst_mode : 1,
> - redir_hint : 1,
> - trigger_mode : 1,
> - dlvry_mode : 3,
> - avail : 4,
> - __reserved_1 : 4,
> - vector : 8,
> - __reserved_2 : 8,
> - dest_id : 32;
> + __u64 present : 1, /* 0 */
> + fpd : 1, /* 1 */
> + __res0 : 6, /* 2 - 6 */
> + avail : 4, /* 8 - 11 */
> + __res1 : 3, /* 12 - 14 */
> + posted : 1, /* 15 */
> + vector : 8, /* 16 - 23 */
> + __res2 : 40; /* 24 - 63 */
> + };
> +
> + /* Remap mode */
> + struct {
> + __u64 r_present : 1, /* 0 */
> + r_fpd : 1, /* 1 */
> + dst_mode : 1, /* 2 */
> + redir_hint : 1, /* 3 */
> + trigger_mode : 1, /* 4 */
> + dlvry_mode : 3, /* 5 - 7 */
> + r_avail : 4, /* 8 - 11 */
> + r_res1 : 4, /* 12 - 13 */
> + r_posted : 1, /* 15 */
> + r_vector : 8, /* 16 - 23 */
> + r_res2 : 8, /* 24 - 31 */
> + dest_id : 32; /* 32 - 63 */
> + };
> +
> + /* Posted mode */
> + struct {
> + __u64 p_present : 1, /* 0 */
> + p_fpd : 1, /* 1 */
> + p_res0 : 6, /* 2 - 6 */
> + p_avail : 4, /* 8 - 11 */
> + p_res1 : 4, /* 12 - 13 */
> + p_urgent : 1, /* 14 */
> + p_posted : 1, /* 15 */
> + p_vector : 8, /* 16 - 23 */
> + p_res2 : 14, /* 24 - 37 */
> + pda_l : 26; /* 38 - 63 */
> };
> __u64 low;
> };
>
> union {
> + /* Shared between remap and posted mode*/
> + struct {
> + __u64 sid : 16, /* 64 - 79 */
> + sq : 2, /* 80 - 81 */
> + svt : 2, /* 82 - 83 */
> + __res3 : 44; /* 84 - 127 */
> + };
> +
> + /* Posted mode*/
> struct {
> - __u64 sid : 16,
> - sq : 2,
> - svt : 2,
> - __reserved_3 : 44;
> + __u64 p_sid : 16, /* 64 - 79 */
> + p_sq : 2, /* 80 - 81 */
> + p_svt : 2, /* 82 - 83 */
> + p_res3 : 12, /* 84 - 95 */
> + pda_h : 32; /* 96 - 127 */
> };
> __u64 high;
> };
This looks great, thanks for your suggestion!
In fact, I also thought about combining this two formats into one structure,
but I encountered two problems:
1. Need change the current remapping code which uses this structure.
2. Building errors.
You patch solves the first issue by generating a shared part in the union,
and based on that it is easy to address the build error issue by renaming
the members.
Thanks,
Feng
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