Hi all,
Beginning from commit 4138cc3418f5, ioremap_nocache() sets the _PAGE_PWT
flag.
Lguest doesn't accept a guest pte with a _PWT flag and reports a
"bad page table entry" in that case.
I've removed check from lguest code and everything worked fine.
Is this safe from the Lguest side ?
Mentioned commit [*]:
commit 4138cc3418f5eaa7524ff8e927102863f1ba0ea5
Author: Siddha, Suresh B <[email protected]>
Date: Wed Jan 30 13:33:43 2008 +0100
x86: set strong uncacheable where UC is really desired
Also use _PAGE_PWT for all the mappings which need uncache mapping.
Instead of existing PAT2 which is UC- (and can be overwritten by MTRRs),
we now use PAT3 which is strong uncacheable.
This makes it consistent with pgprot_noncached()
diff --git a/arch/x86/mm/ioremap_32.c b/arch/x86/mm/ioremap_32.c
index 0b27831..ef0f6a4 100644
--- a/arch/x86/mm/ioremap_32.c
+++ b/arch/x86/mm/ioremap_32.c
@@ -119,7 +119,7 @@ EXPORT_SYMBOL(__ioremap);
void __iomem *ioremap_nocache (unsigned long phys_addr, unsigned long size)
{
unsigned long last_addr;
- void __iomem *p = __ioremap(phys_addr, size, _PAGE_PCD);
+ void __iomem *p = __ioremap(phys_addr, size, _PAGE_PCD | _PAGE_PWT);
if (!p)
return p;
Thanks,
[*]: latest pull calls set_memory_uc() which also sets the _PWT flag.
--
Ahmed S. Darwish
Homepage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com
* Ahmed S. Darwish <[email protected]> wrote:
> Hi all,
>
> Beginning from commit 4138cc3418f5, ioremap_nocache() sets the _PAGE_PWT
> flag.
>
> Lguest doesn't accept a guest pte with a _PWT flag and reports a "bad
> page table entry" in that case.
>
> I've removed check from lguest code and everything worked fine. Is
> this safe from the Lguest side ?
yes, should be safe. Could you send a patch so that others can apply it
too?
Ingo
On Thu, Feb 07, 2008 at 12:59:23AM +0100, Ingo Molnar wrote:
>
> * Ahmed S. Darwish <[email protected]> wrote:
>
> > Hi all,
> >
> > Beginning from commit 4138cc3418f5, ioremap_nocache() sets the _PAGE_PWT
> > flag.
> >
> > Lguest doesn't accept a guest pte with a _PWT flag and reports a "bad
> > page table entry" in that case.
> >
> > I've removed check from lguest code and everything worked fine. Is
> > this safe from the Lguest side ?
>
> yes, should be safe. Could you send a patch so that others can apply it
> too?
>
Ofcourse :) :
Accept guest _PAGE_PWT page table entries, otherwise lguest will
always fail with a "bad page table entry" message.
Signed-off-by: Ahmed S. Darwish <[email protected]>
---
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
index 74b4cf2..952160b 100644
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -178,8 +178,8 @@ static void release_pte(pte_t pte)
static void check_gpte(struct lg_cpu *cpu, pte_t gpte)
{
- if ((pte_flags(gpte) & (_PAGE_PWT|_PAGE_PSE))
- || pte_pfn(gpte) >= cpu->lg->pfn_limit)
+ if ((pte_flags(gpte) & _PAGE_PSE) ||
+ pte_pfn(gpte) >= cpu->lg->pfn_limit)
kill_guest(cpu, "bad page table entry");
}
Regards,
--
Ahmed S. Darwish
Homepage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com
* Ahmed S. Darwish <[email protected]> wrote:
> Ofcourse :) :
>
> Accept guest _PAGE_PWT page table entries, otherwise lguest will
> always fail with a "bad page table entry" message.
thanks - i've queued this up into x86.git. Rusty, is this fine to you,
and should we nurse this fix upstream?
Ingo
On Thursday 07 February 2008 11:51:20 Ahmed S. Darwish wrote:
> On Thu, Feb 07, 2008 at 12:59:23AM +0100, Ingo Molnar wrote:
> > yes, should be safe. Could you send a patch so that others can apply it
> > too?
>
> Ofcourse :) :
>
> Accept guest _PAGE_PWT page table entries, otherwise lguest will
> always fail with a "bad page table entry" message.
>
> Signed-off-by: Ahmed S. Darwish <[email protected]>
Thanks for tracking this Ahmed, and thanks to Ingo for pushing it upstream.
Cheers,
Rusty.