linux-kernel - Re: [PATCH v3] x86, tboot: iomem fixes

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Message-ID: <20130719075947.GC22597@gmail.com>
Date:	Fri, 19 Jul 2013 09:59:47 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	"Ren, Qiaowei" <qiaowei.ren@...el.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Wei, Gang" <gang.wei@...el.com>
Subject: Re: [PATCH v3] x86, tboot: iomem fixes


* Ren, Qiaowei <qiaowei.ren@...el.com> wrote:

> On 2013-07-18, Ingo Molnar wrote:
> > 
> > * Qiaowei Ren <qiaowei.ren@...el.com> wrote:
> > 
> >> Current code doesn't use specific interface to access I/O space.
> >> So some potential bugs can be caused. We can fix this by using
> >> specific API.
> > 
> > This is still very vague.
> > 
> >> 
> >> Signed-off-by: Qiaowei Ren <qiaowei.ren@...el.com>
> >> ---
> >>  arch/x86/kernel/tboot.c |   21 ++++++++++++---------
> >>  1 file changed, 12 insertions(+), 9 deletions(-)
> >> diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c index
> >> 3ff42d2..afe8cf8 100644
> >> --- a/arch/x86/kernel/tboot.c
> >> +++ b/arch/x86/kernel/tboot.c
> >> @@ -466,9 +466,12 @@ struct sinit_mle_data {
> >>  	u32               vtd_dmars_off;
> >>  } __packed;
> >> +#define SINIT_MLE_DATA_VTD_DMAR_OFF	140
> >> +
> >>  struct acpi_table_header *tboot_get_dmar_table(struct
> >> acpi_table_header *dmar_tbl)  {
> >> -	void *heap_base, *heap_ptr, *config;
> >> +	void __iomem *heap_base, *heap_ptr, *config;
> >> +	u32 dmar_tbl_off;
> >> 
> >>  	if (!tboot_enabled())
> >>  		return dmar_tbl;
> >> @@ -485,25 +488,25 @@ struct acpi_table_header
> > *tboot_get_dmar_table(struct acpi_table_header *dmar_tb
> >>  		return NULL;
> >>  
> >>  	/* now map TXT heap */
> >> -	heap_base = ioremap(*(u64 *)(config + TXTCR_HEAP_BASE),
> >> -			    *(u64 *)(config + TXTCR_HEAP_SIZE));
> >> +	heap_base = ioremap(readl(config + TXTCR_HEAP_BASE),
> >> +			    readl(config + TXTCR_HEAP_SIZE));
> >>  	iounmap(config);
> >>  	if (!heap_base)
> >>  		return NULL;
> >>  
> >>  	/* walk heap to SinitMleData */
> >>  	/* skip BiosData */
> >> -	heap_ptr = heap_base + *(u64 *)heap_base;
> >> +	heap_ptr = heap_base + readq(heap_base);
> >>  	/* skip OsMleData */
> >> -	heap_ptr += *(u64 *)heap_ptr;
> >> +	heap_ptr += readq(heap_ptr);
> >>  	/* skip OsSinitData */
> >> -	heap_ptr += *(u64 *)heap_ptr;
> >> +	heap_ptr += readq(heap_ptr);
> >>  	/* now points to SinitMleDataSize; set to SinitMleData */
> >>  	heap_ptr += sizeof(u64);
> >>  	/* get addr of DMAR table */
> >> -	dmar_tbl = (struct acpi_table_header *)(heap_ptr +
> >> -		   ((struct sinit_mle_data *)heap_ptr)->vtd_dmars_off -
> >> -		   sizeof(u64));
> >> +	dmar_tbl_off = readl(heap_ptr + SINIT_MLE_DATA_VTD_DMAR_OFF);
> >> +	memcpy_fromio(dmar_tbl, heap_ptr + dmar_tbl_off - sizeof(u64),
> >> +			sizeof(struct acpi_table_header));
> > 
> > That memcpy (or an equivalent of it) was not in the code before, AFAICS.
> > 
> > How can this be an 'interface fix'? It adds in new code...
> > 
> Sorry, current code only need to get addr of DMAR table, so memcpy_fromio may be removed, even though this will also work.
> So "memcpy_fromio" line will be changed to 
> 	dmar_tbl = (struct acpi_table_header *)(heap_ptr + dmar_tbl_off + - sizeof(u64));
> If so, no new interface will be added, and the changelog at the beginning of this patch is engouch?

Please resubmit the fixed patch so I can have a fresh look.

Thanks,

	Ingo
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