[PATCH] documentation, refactor, and cleanups (v2) for 3.7

[PATCH] documentation, refactor, and cleanups (v2) for 3.7

[Konrad Rzeszutek Wilk]

Attached are four patches that documented a bit more the P2M and MMU
code. And as well make some of the code cleaner and easier to read.

[PATCH 1/4] xen/p2m: Fix the comment describing the P2M tree.

[Konrad Rzeszutek Wilk]

It mixed up the p2m_mid_missing with p2m_missing. Also
remove some extra spaces.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/xen/p2m.c |   14 +++++++-------
 1 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 64effdc..e4adbfb 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -22,7 +22,7 @@
  *
  * P2M_PER_PAGE depends on the architecture, as a mfn is always
  * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to
- * 512 and 1024 entries respectively. 
+ * 512 and 1024 entries respectively.
  *
  * In short, these structures contain the Machine Frame Number (MFN) of the PFN.
  *
@@ -139,11 +139,11 @@
  *      /    | ~0, ~0, ....  |
  *     |     \---------------/
  *     |
- *     p2m_missing             p2m_missing
- * /------------------\     /------------\
- * | [p2m_mid_missing]+---->| ~0, ~0, ~0 |
- * | [p2m_mid_missing]+---->| ..., ~0    |
- * \------------------/     \------------/
+ *   p2m_mid_missing           p2m_missing
+ * /-----------------\     /------------\
+ * | [p2m_missing]   +---->| ~0, ~0, ~0 |
+ * | [p2m_missing]   +---->| ..., ~0    |
+ * \-----------------/     \------------/
  *
  * where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT)
  */
@@ -423,7 +423,7 @@ static void free_p2m_page(void *p)
 	free_page((unsigned long)p);
 }
 
-/* 
+/*
  * Fully allocate the p2m structure for a given pfn.  We need to check
  * that both the top and mid levels are allocated, and make sure the
  * parallel mfn tree is kept in sync.  We may race with other cpus, so
-- 
1.7.7.6

[PATCH 2/4] xen/x86: Use memblock_reserve for sensitive areas.

[Konrad Rzeszutek Wilk]

instead of a big memblock_reserve. This way we can be more
selective in freeing regions (and it also makes it easier
to understand where is what).

[v1: Move the auto_translate_physmap to proper line]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/xen/enlighten.c |   38 ++++++++++++++++++++++++++++++++++++++
 arch/x86/xen/p2m.c       |    5 +++++
 arch/x86/xen/setup.c     |    9 ---------
 3 files changed, 43 insertions(+), 9 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index ff962d4..9b1afa4 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -998,7 +998,44 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
 
 	return ret;
 }
+static void __init xen_reserve_mfn(unsigned long mfn)
+{
+	unsigned long pfn;
+
+	if (!mfn)
+		return;
+	pfn = mfn_to_pfn(mfn);
+	if (phys_to_machine_mapping_valid(pfn))
+		memblock_reserve(PFN_PHYS(pfn), PAGE_SIZE);
+}
+static void __init xen_reserve_internals(void)
+{
+	unsigned long size;
+
+	if (!xen_pv_domain())
+		return;
+
+	memblock_reserve(__pa(xen_start_info), PAGE_SIZE);
+
+	xen_reserve_mfn(PFN_DOWN(xen_start_info->shared_info));
+	xen_reserve_mfn(xen_start_info->store_mfn);
 
+	if (!xen_initial_domain())
+		xen_reserve_mfn(xen_start_info->console.domU.mfn);
+
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return;
+
+	/*
+	 * ALIGN up to compensate for the p2m_page pointing to an array that
+	 * can partially filled (look in xen_build_dynamic_phys_to_machine).
+	 */
+
+	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
+	memblock_reserve(__pa(xen_start_info->mfn_list), size);
+
+	/* The pagetables are reserved in mmu.c */
+}
 void xen_setup_shared_info(void)
 {
 	if (!xen_feature(XENFEAT_auto_translated_physmap)) {
@@ -1362,6 +1399,7 @@ asmlinkage void __init xen_start_kernel(void)
 	xen_raw_console_write("mapping kernel into physical memory\n");
 	pgd = xen_setup_kernel_pagetable(pgd, xen_start_info->nr_pages);
 
+	xen_reserve_internals();
 	/* Allocate and initialize top and mid mfn levels for p2m structure */
 	xen_build_mfn_list_list();
 
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index e4adbfb..6a2bfa4 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -388,6 +388,11 @@ void __init xen_build_dynamic_phys_to_machine(void)
 	}
 
 	m2p_override_init();
+
+	/* NOTE: We cannot call memblock_reserve here for the mfn_list as there
+	 * isn't enough pieces to make it work (for one - we are still using the
+	 * Xen provided pagetable). Do it later in xen_reserve_internals.
+	 */
 }
 
 unsigned long get_phys_to_machine(unsigned long pfn)
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index a4790bf..9efca75 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -424,15 +424,6 @@ char * __init xen_memory_setup(void)
 	e820_add_region(ISA_START_ADDRESS, ISA_END_ADDRESS - ISA_START_ADDRESS,
 			E820_RESERVED);
 
-	/*
-	 * Reserve Xen bits:
-	 *  - mfn_list
-	 *  - xen_start_info
-	 * See comment above "struct start_info" in <xen/interface/xen.h>
-	 */
-	memblock_reserve(__pa(xen_start_info->mfn_list),
-			 xen_start_info->pt_base - xen_start_info->mfn_list);
-
 	sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
 
 	return "Xen";
-- 
1.7.7.6

Re: [PATCH 2/4] xen/x86: Use memblock_reserve for sensitive areas.

[Stefano Stabellini]

On Thu, 26 Jul 2012, Konrad Rzeszutek Wilk wrote:
> instead of a big memblock_reserve. This way we can be more
> selective in freeing regions (and it also makes it easier
> to understand where is what).
> 
> [v1: Move the auto_translate_physmap to proper line]
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  arch/x86/xen/enlighten.c |   38 ++++++++++++++++++++++++++++++++++++++
>  arch/x86/xen/p2m.c       |    5 +++++
>  arch/x86/xen/setup.c     |    9 ---------
>  3 files changed, 43 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index ff962d4..9b1afa4 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -998,7 +998,44 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
>  
>  	return ret;
>  }
> +static void __init xen_reserve_mfn(unsigned long mfn)
> +{
> +	unsigned long pfn;
> +
> +	if (!mfn)
> +		return;
> +	pfn = mfn_to_pfn(mfn);
> +	if (phys_to_machine_mapping_valid(pfn))
> +		memblock_reserve(PFN_PHYS(pfn), PAGE_SIZE);
> +}

If the mfn is not in the m2p xen_reserve_mfn won't do anything. It is
worth writing it down in a comment.


> +static void __init xen_reserve_internals(void)
> +{
> +	unsigned long size;
> +
> +	if (!xen_pv_domain())
> +		return;
> +
> +	memblock_reserve(__pa(xen_start_info), PAGE_SIZE);

xen_start_info is not in the m2p, so you cannot use xen_reserve_mfn


> +	xen_reserve_mfn(PFN_DOWN(xen_start_info->shared_info));
> +	xen_reserve_mfn(xen_start_info->store_mfn);

Are we sure that shared_info points to an mfn that is in the m2p (rather
than a special mfn not present in the list)?


> +	if (!xen_initial_domain())
> +		xen_reserve_mfn(xen_start_info->console.domU.mfn);
> +
> +	if (xen_feature(XENFEAT_auto_translated_physmap))
> +		return;
> +
> +	/*
> +	 * ALIGN up to compensate for the p2m_page pointing to an array that
> +	 * can partially filled (look in xen_build_dynamic_phys_to_machine).
> +	 */
> +
> +	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
> +	memblock_reserve(__pa(xen_start_info->mfn_list), size);

I take that here you are using memblock_reserve again, rather than
xen_reserve_mfn, because the corresponding mfn is not in the m2p?


> +	/* The pagetables are reserved in mmu.c */
> +}
>  void xen_setup_shared_info(void)
>  {
>  	if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> @@ -1362,6 +1399,7 @@ asmlinkage void __init xen_start_kernel(void)
>  	xen_raw_console_write("mapping kernel into physical memory\n");
>  	pgd = xen_setup_kernel_pagetable(pgd, xen_start_info->nr_pages);
>  
> +	xen_reserve_internals();
>  	/* Allocate and initialize top and mid mfn levels for p2m structure */
>  	xen_build_mfn_list_list();
>  
> diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
> index e4adbfb..6a2bfa4 100644
> --- a/arch/x86/xen/p2m.c
> +++ b/arch/x86/xen/p2m.c
> @@ -388,6 +388,11 @@ void __init xen_build_dynamic_phys_to_machine(void)
>  	}
>  
>  	m2p_override_init();
> +
> +	/* NOTE: We cannot call memblock_reserve here for the mfn_list as there
> +	 * isn't enough pieces to make it work (for one - we are still using the
> +	 * Xen provided pagetable). Do it later in xen_reserve_internals.
> +	 */
>  }
>  
>  unsigned long get_phys_to_machine(unsigned long pfn)
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index a4790bf..9efca75 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -424,15 +424,6 @@ char * __init xen_memory_setup(void)
>  	e820_add_region(ISA_START_ADDRESS, ISA_END_ADDRESS - ISA_START_ADDRESS,
>  			E820_RESERVED);
>  
> -	/*
> -	 * Reserve Xen bits:
> -	 *  - mfn_list
> -	 *  - xen_start_info
> -	 * See comment above "struct start_info" in <xen/interface/xen.h>
> -	 */
> -	memblock_reserve(__pa(xen_start_info->mfn_list),
> -			 xen_start_info->pt_base - xen_start_info->mfn_list);
> -
>  	sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
>  
>  	return "Xen";
> -- 
> 1.7.7.6
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
> 

Re: [Xen-devel] [PATCH 2/4] xen/x86: Use memblock_reserve for sensitive areas.

[Konrad Rzeszutek Wilk]

On Fri, Jul 27, 2012 at 11:49:02AM +0100, Stefano Stabellini wrote:
> On Thu, 26 Jul 2012, Konrad Rzeszutek Wilk wrote:
> > instead of a big memblock_reserve. This way we can be more
> > selective in freeing regions (and it also makes it easier
> > to understand where is what).
> > 
> > [v1: Move the auto_translate_physmap to proper line]
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > ---
> >  arch/x86/xen/enlighten.c |   38 ++++++++++++++++++++++++++++++++++++++
> >  arch/x86/xen/p2m.c       |    5 +++++
> >  arch/x86/xen/setup.c     |    9 ---------
> >  3 files changed, 43 insertions(+), 9 deletions(-)
> > 
> > diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> > index ff962d4..9b1afa4 100644
> > --- a/arch/x86/xen/enlighten.c
> > +++ b/arch/x86/xen/enlighten.c
> > @@ -998,7 +998,44 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
> >  
> >  	return ret;
> >  }
> > +static void __init xen_reserve_mfn(unsigned long mfn)
> > +{
> > +	unsigned long pfn;
> > +
> > +	if (!mfn)
> > +		return;
> > +	pfn = mfn_to_pfn(mfn);
> > +	if (phys_to_machine_mapping_valid(pfn))
> > +		memblock_reserve(PFN_PHYS(pfn), PAGE_SIZE);
> > +}
> 
> If the mfn is not in the m2p xen_reserve_mfn won't do anything. It is
> worth writing it down in a comment.

Meaning in a printk?
> 
> 
> > +static void __init xen_reserve_internals(void)
> > +{
> > +	unsigned long size;
> > +
> > +	if (!xen_pv_domain())
> > +		return;
> > +
> > +	memblock_reserve(__pa(xen_start_info), PAGE_SIZE);
> 
> xen_start_info is not in the m2p, so you cannot use xen_reserve_mfn

It seems to work for me. For both the toolstack created guests
and dom0. Let me double check thought.
> 
> 
> > +	xen_reserve_mfn(PFN_DOWN(xen_start_info->shared_info));
> > +	xen_reserve_mfn(xen_start_info->store_mfn);
> 
> Are we sure that shared_info points to an mfn that is in the m2p (rather
> than a special mfn not present in the list)?
> 
> 
> > +	if (!xen_initial_domain())
> > +		xen_reserve_mfn(xen_start_info->console.domU.mfn);
> > +
> > +	if (xen_feature(XENFEAT_auto_translated_physmap))
> > +		return;
> > +
> > +	/*
> > +	 * ALIGN up to compensate for the p2m_page pointing to an array that
> > +	 * can partially filled (look in xen_build_dynamic_phys_to_machine).
> > +	 */
> > +
> > +	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
> > +	memblock_reserve(__pa(xen_start_info->mfn_list), size);
> 
> I take that here you are using memblock_reserve again, rather than
> xen_reserve_mfn, because the corresponding mfn is not in the m2p?

<nods> Well, they are - but they are 55555555..
> 
> 
> > +	/* The pagetables are reserved in mmu.c */
> > +}
> >  void xen_setup_shared_info(void)
> >  {
> >  	if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> > @@ -1362,6 +1399,7 @@ asmlinkage void __init xen_start_kernel(void)
> >  	xen_raw_console_write("mapping kernel into physical memory\n");
> >  	pgd = xen_setup_kernel_pagetable(pgd, xen_start_info->nr_pages);
> >  
> > +	xen_reserve_internals();
> >  	/* Allocate and initialize top and mid mfn levels for p2m structure */
> >  	xen_build_mfn_list_list();
> >  
> > diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
> > index e4adbfb..6a2bfa4 100644
> > --- a/arch/x86/xen/p2m.c
> > +++ b/arch/x86/xen/p2m.c
> > @@ -388,6 +388,11 @@ void __init xen_build_dynamic_phys_to_machine(void)
> >  	}
> >  
> >  	m2p_override_init();
> > +
> > +	/* NOTE: We cannot call memblock_reserve here for the mfn_list as there
> > +	 * isn't enough pieces to make it work (for one - we are still using the
> > +	 * Xen provided pagetable). Do it later in xen_reserve_internals.
> > +	 */
> >  }
> >  
> >  unsigned long get_phys_to_machine(unsigned long pfn)
> > diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> > index a4790bf..9efca75 100644
> > --- a/arch/x86/xen/setup.c
> > +++ b/arch/x86/xen/setup.c
> > @@ -424,15 +424,6 @@ char * __init xen_memory_setup(void)
> >  	e820_add_region(ISA_START_ADDRESS, ISA_END_ADDRESS - ISA_START_ADDRESS,
> >  			E820_RESERVED);
> >  
> > -	/*
> > -	 * Reserve Xen bits:
> > -	 *  - mfn_list
> > -	 *  - xen_start_info
> > -	 * See comment above "struct start_info" in <xen/interface/xen.h>
> > -	 */
> > -	memblock_reserve(__pa(xen_start_info->mfn_list),
> > -			 xen_start_info->pt_base - xen_start_info->mfn_list);
> > -
> >  	sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
> >  
> >  	return "Xen";
> > -- 
> > 1.7.7.6
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> > 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 2/4] xen/x86: Use memblock_reserve for sensitive areas.

[Stefano Stabellini]

On Fri, 27 Jul 2012, Konrad Rzeszutek Wilk wrote:
> On Fri, Jul 27, 2012 at 11:49:02AM +0100, Stefano Stabellini wrote:
> > On Thu, 26 Jul 2012, Konrad Rzeszutek Wilk wrote:
> > > instead of a big memblock_reserve. This way we can be more
> > > selective in freeing regions (and it also makes it easier
> > > to understand where is what).
> > > 
> > > [v1: Move the auto_translate_physmap to proper line]
> > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > > ---
> > >  arch/x86/xen/enlighten.c |   38 ++++++++++++++++++++++++++++++++++++++
> > >  arch/x86/xen/p2m.c       |    5 +++++
> > >  arch/x86/xen/setup.c     |    9 ---------
> > >  3 files changed, 43 insertions(+), 9 deletions(-)
> > > 
> > > diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> > > index ff962d4..9b1afa4 100644
> > > --- a/arch/x86/xen/enlighten.c
> > > +++ b/arch/x86/xen/enlighten.c
> > > @@ -998,7 +998,44 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
> > >  
> > >  	return ret;
> > >  }
> > > +static void __init xen_reserve_mfn(unsigned long mfn)
> > > +{
> > > +	unsigned long pfn;
> > > +
> > > +	if (!mfn)
> > > +		return;
> > > +	pfn = mfn_to_pfn(mfn);
> > > +	if (phys_to_machine_mapping_valid(pfn))
> > > +		memblock_reserve(PFN_PHYS(pfn), PAGE_SIZE);
> > > +}
> > 
> > If the mfn is not in the m2p xen_reserve_mfn won't do anything. It is
> > worth writing it down in a comment.
> 
> Meaning in a printk?

I meant a comment in the code.


> > > +static void __init xen_reserve_internals(void)
> > > +{
> > > +	unsigned long size;
> > > +
> > > +	if (!xen_pv_domain())
> > > +		return;
> > > +
> > > +	memblock_reserve(__pa(xen_start_info), PAGE_SIZE);
> > 
> > xen_start_info is not in the m2p, so you cannot use xen_reserve_mfn
> 
> It seems to work for me. For both the toolstack created guests
> and dom0. Let me double check thought.

I was just thinking out loud: you are calling memblock_reserve rather
than xen_reserve_mfn, because xen_reserve_mfn wouldn't work in this case
as xen_start_info is not in the m2p.

[PATCH 3/4] xen/mmu: The xen_setup_kernel_pagetable doesn't need to return anything.

[Konrad Rzeszutek Wilk]

We don't need to return the new PGD - as we do not use it.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/xen/enlighten.c |    5 +----
 arch/x86/xen/mmu.c       |   10 ++--------
 arch/x86/xen/xen-ops.h   |    2 +-
 3 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 9b1afa4..2b67948 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1295,7 +1295,6 @@ asmlinkage void __init xen_start_kernel(void)
 {
 	struct physdev_set_iopl set_iopl;
 	int rc;
-	pgd_t *pgd;
 
 	if (!xen_start_info)
 		return;
@@ -1387,8 +1386,6 @@ asmlinkage void __init xen_start_kernel(void)
 	acpi_numa = -1;
 #endif
 
-	pgd = (pgd_t *)xen_start_info->pt_base;
-
 	/* Don't do the full vcpu_info placement stuff until we have a
 	   possible map and a non-dummy shared_info. */
 	per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];
@@ -1397,7 +1394,7 @@ asmlinkage void __init xen_start_kernel(void)
 	early_boot_irqs_disabled = true;
 
 	xen_raw_console_write("mapping kernel into physical memory\n");
-	pgd = xen_setup_kernel_pagetable(pgd, xen_start_info->nr_pages);
+	xen_setup_kernel_pagetable((pgd_t *)xen_start_info->pt_base, xen_start_info->nr_pages);
 
 	xen_reserve_internals();
 	/* Allocate and initialize top and mid mfn levels for p2m structure */
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 3a73785..4ac21a4 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1719,8 +1719,7 @@ static void convert_pfn_mfn(void *v)
  * of the physical mapping once some sort of allocator has been set
  * up.
  */
-pgd_t * __init xen_setup_kernel_pagetable(pgd_t *pgd,
-					 unsigned long max_pfn)
+void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
 {
 	pud_t *l3;
 	pmd_t *l2;
@@ -1781,8 +1780,6 @@ pgd_t * __init xen_setup_kernel_pagetable(pgd_t *pgd,
 
 	memblock_reserve(__pa(xen_start_info->pt_base),
 			 xen_start_info->nr_pt_frames * PAGE_SIZE);
-
-	return pgd;
 }
 #else	/* !CONFIG_X86_64 */
 static RESERVE_BRK_ARRAY(pmd_t, initial_kernel_pmd, PTRS_PER_PMD);
@@ -1825,8 +1822,7 @@ static void __init xen_write_cr3_init(unsigned long cr3)
 	pv_mmu_ops.write_cr3 = &xen_write_cr3;
 }
 
-pgd_t * __init xen_setup_kernel_pagetable(pgd_t *pgd,
-					 unsigned long max_pfn)
+void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
 {
 	pmd_t *kernel_pmd;
 
@@ -1858,8 +1854,6 @@ pgd_t * __init xen_setup_kernel_pagetable(pgd_t *pgd,
 
 	memblock_reserve(__pa(xen_start_info->pt_base),
 			 xen_start_info->nr_pt_frames * PAGE_SIZE);
-
-	return initial_page_table;
 }
 #endif	/* CONFIG_X86_64 */
 
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 202d4c1..2230f57 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -27,7 +27,7 @@ void xen_setup_mfn_list_list(void);
 void xen_setup_shared_info(void);
 void xen_build_mfn_list_list(void);
 void xen_setup_machphys_mapping(void);
-pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
+void xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
 void xen_reserve_top(void);
 extern unsigned long xen_max_p2m_pfn;
 
-- 
1.7.7.6

Re: [PATCH 3/4] xen/mmu: The xen_setup_kernel_pagetable doesn't need to return anything.

[Stefano Stabellini]

On Thu, 26 Jul 2012, Konrad Rzeszutek Wilk wrote:
> We don't need to return the new PGD - as we do not use it.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>


Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

>  arch/x86/xen/enlighten.c |    5 +----
>  arch/x86/xen/mmu.c       |   10 ++--------
>  arch/x86/xen/xen-ops.h   |    2 +-
>  3 files changed, 4 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 9b1afa4..2b67948 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1295,7 +1295,6 @@ asmlinkage void __init xen_start_kernel(void)
>  {
>  	struct physdev_set_iopl set_iopl;
>  	int rc;
> -	pgd_t *pgd;
>  
>  	if (!xen_start_info)
>  		return;
> @@ -1387,8 +1386,6 @@ asmlinkage void __init xen_start_kernel(void)
>  	acpi_numa = -1;
>  #endif
>  
> -	pgd = (pgd_t *)xen_start_info->pt_base;
> -
>  	/* Don't do the full vcpu_info placement stuff until we have a
>  	   possible map and a non-dummy shared_info. */
>  	per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];
> @@ -1397,7 +1394,7 @@ asmlinkage void __init xen_start_kernel(void)
>  	early_boot_irqs_disabled = true;
>  
>  	xen_raw_console_write("mapping kernel into physical memory\n");
> -	pgd = xen_setup_kernel_pagetable(pgd, xen_start_info->nr_pages);
> +	xen_setup_kernel_pagetable((pgd_t *)xen_start_info->pt_base, xen_start_info->nr_pages);
>  
>  	xen_reserve_internals();
>  	/* Allocate and initialize top and mid mfn levels for p2m structure */
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index 3a73785..4ac21a4 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -1719,8 +1719,7 @@ static void convert_pfn_mfn(void *v)
>   * of the physical mapping once some sort of allocator has been set
>   * up.
>   */
> -pgd_t * __init xen_setup_kernel_pagetable(pgd_t *pgd,
> -					 unsigned long max_pfn)
> +void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
>  {
>  	pud_t *l3;
>  	pmd_t *l2;
> @@ -1781,8 +1780,6 @@ pgd_t * __init xen_setup_kernel_pagetable(pgd_t *pgd,
>  
>  	memblock_reserve(__pa(xen_start_info->pt_base),
>  			 xen_start_info->nr_pt_frames * PAGE_SIZE);
> -
> -	return pgd;
>  }
>  #else	/* !CONFIG_X86_64 */
>  static RESERVE_BRK_ARRAY(pmd_t, initial_kernel_pmd, PTRS_PER_PMD);
> @@ -1825,8 +1822,7 @@ static void __init xen_write_cr3_init(unsigned long cr3)
>  	pv_mmu_ops.write_cr3 = &xen_write_cr3;
>  }
>  
> -pgd_t * __init xen_setup_kernel_pagetable(pgd_t *pgd,
> -					 unsigned long max_pfn)
> +void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
>  {
>  	pmd_t *kernel_pmd;
>  
> @@ -1858,8 +1854,6 @@ pgd_t * __init xen_setup_kernel_pagetable(pgd_t *pgd,
>  
>  	memblock_reserve(__pa(xen_start_info->pt_base),
>  			 xen_start_info->nr_pt_frames * PAGE_SIZE);
> -
> -	return initial_page_table;
>  }
>  #endif	/* CONFIG_X86_64 */
>  
> diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
> index 202d4c1..2230f57 100644
> --- a/arch/x86/xen/xen-ops.h
> +++ b/arch/x86/xen/xen-ops.h
> @@ -27,7 +27,7 @@ void xen_setup_mfn_list_list(void);
>  void xen_setup_shared_info(void);
>  void xen_build_mfn_list_list(void);
>  void xen_setup_machphys_mapping(void);
> -pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
> +void xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
>  void xen_reserve_top(void);
>  extern unsigned long xen_max_p2m_pfn;
>  
> -- 
> 1.7.7.6
> 
> --
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> 

[PATCH 4/4] xen/mmu: Provide comments describing the _ka and _va aliasing issue

[Konrad Rzeszutek Wilk]

Which is that the level2_kernel_pgt (__ka virtual addresses)
and level2_ident_pgt (__va virtual address) contain the same
PMD entries. So if you modify a PTE in __ka, it will be reflected
in __va (and vice-versa).

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/xen/mmu.c |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 4ac21a4..6ba6100 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1734,19 +1734,36 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
 	init_level4_pgt[0] = __pgd(0);
 
 	/* Pre-constructed entries are in pfn, so convert to mfn */
+	/* L4[272] -> level3_ident_pgt
+	 * L4[511] -> level3_kernel_pgt */
 	convert_pfn_mfn(init_level4_pgt);
+
+	/* L3_i[0] -> level2_ident_pgt */
 	convert_pfn_mfn(level3_ident_pgt);
+	/* L3_k[510] -> level2_kernel_pgt
+	 * L3_i[511] -> level2_fixmap_pgt */
 	convert_pfn_mfn(level3_kernel_pgt);
 
+	/* We get [511][511] and have Xen's version of level2_kernel_pgt */
 	l3 = m2v(pgd[pgd_index(__START_KERNEL_map)].pgd);
 	l2 = m2v(l3[pud_index(__START_KERNEL_map)].pud);
 
+	/* Graft it onto L4[272][0]. Note that we creating an aliasing problem:
+	 * Both L4[272][0] and L4[511][511] have entries that point to the same
+	 * L2 (PMD) tables. Meaning that if you modify it in __va space
+	 * it will be also modified in the __ka space! (But if you just
+	 * modify the PMD table to point to other PTE's or none, then you
+	 * are OK - which is what cleanup_highmap does) */
 	memcpy(level2_ident_pgt, l2, sizeof(pmd_t) * PTRS_PER_PMD);
+	/* Graft it onto L4[511][511] */
 	memcpy(level2_kernel_pgt, l2, sizeof(pmd_t) * PTRS_PER_PMD);
 
+	/* Get [511][510] and graft that in level2_fixmap_pgt */
 	l3 = m2v(pgd[pgd_index(__START_KERNEL_map + PMD_SIZE)].pgd);
 	l2 = m2v(l3[pud_index(__START_KERNEL_map + PMD_SIZE)].pud);
 	memcpy(level2_fixmap_pgt, l2, sizeof(pmd_t) * PTRS_PER_PMD);
+	/* Note that we don't do anything with level1_fixmap_pgt which
+	 * we don't need. */
 
 	/* Set up identity map */
 	xen_map_identity_early(level2_ident_pgt, max_pfn);
-- 
1.7.7.6