2010-11-11 13:56:58

by Joerg Roedel

[permalink] [raw]
Subject: [PATCH 2/3] x86, mm: Fix CONFIG_VMSPLIT_1G and 2G_OPT trampoline

From: Hugh Dickins <[email protected]>

rc2 kernel crashes when booting second cpu on this CONFIG_VMSPLIT_2G_OPT
laptop: whereas cloning from kernel to low mappings pgd range does need
to limit by both KERNEL_PGD_PTRS and KERNEL_PGD_BOUNDARY, cloning kernel
pgd range itself must not be limited by the smaller KERNEL_PGD_BOUNDARY.

Signed-off-by: Hugh Dickins <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
---
arch/x86/kernel/trampoline.c | 3 +--
1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/trampoline.c b/arch/x86/kernel/trampoline.c
index 4e816a4..0ac23a7 100644
--- a/arch/x86/kernel/trampoline.c
+++ b/arch/x86/kernel/trampoline.c
@@ -47,8 +47,7 @@ void __init setup_trampoline_page_table(void)
/* Copy kernel address range */
clone_pgd_range(trampoline_pg_dir + KERNEL_PGD_BOUNDARY,
swapper_pg_dir + KERNEL_PGD_BOUNDARY,
- min_t(unsigned long, KERNEL_PGD_PTRS,
- KERNEL_PGD_BOUNDARY));
+ KERNEL_PGD_PTRS);

/* Initialize low mappings */
clone_pgd_range(trampoline_pg_dir,
--
1.7.0.4


2010-11-11 14:11:00

by Greg KH

[permalink] [raw]
Subject: Re: [PATCH 2/3] x86, mm: Fix CONFIG_VMSPLIT_1G and 2G_OPT trampoline

On Thu, Nov 11, 2010 at 02:56:14PM +0100, Joerg Roedel wrote:
> From: Hugh Dickins <[email protected]>
>
> rc2 kernel crashes when booting second cpu on this CONFIG_VMSPLIT_2G_OPT
> laptop: whereas cloning from kernel to low mappings pgd range does need
> to limit by both KERNEL_PGD_PTRS and KERNEL_PGD_BOUNDARY, cloning kernel
> pgd range itself must not be limited by the smaller KERNEL_PGD_BOUNDARY.
>
> Signed-off-by: Hugh Dickins <[email protected]>
> LKML-Reference: <[email protected]>
> Signed-off-by: H. Peter Anvin <[email protected]>
> ---
> arch/x86/kernel/trampoline.c | 3 +--
> 1 files changed, 1 insertions(+), 2 deletions(-)

Why are you sending this to me? I'm not the x86 maintainer.

confused,

greg k-h

2010-11-11 14:13:11

by Greg KH

[permalink] [raw]
Subject: Re: [PATCH 2/3] x86, mm: Fix CONFIG_VMSPLIT_1G and 2G_OPT trampoline

On Thu, Nov 11, 2010 at 06:11:30AM -0800, Greg KH wrote:
> On Thu, Nov 11, 2010 at 02:56:14PM +0100, Joerg Roedel wrote:
> > From: Hugh Dickins <[email protected]>
> >
> > rc2 kernel crashes when booting second cpu on this CONFIG_VMSPLIT_2G_OPT
> > laptop: whereas cloning from kernel to low mappings pgd range does need
> > to limit by both KERNEL_PGD_PTRS and KERNEL_PGD_BOUNDARY, cloning kernel
> > pgd range itself must not be limited by the smaller KERNEL_PGD_BOUNDARY.
> >
> > Signed-off-by: Hugh Dickins <[email protected]>
> > LKML-Reference: <[email protected]>
> > Signed-off-by: H. Peter Anvin <[email protected]>
> > ---
> > arch/x86/kernel/trampoline.c | 3 +--
> > 1 files changed, 1 insertions(+), 2 deletions(-)
>
> Why are you sending this to me? I'm not the x86 maintainer.

Ah, now it makes more sense (seeing 0/3 after 2/3 came in.)

But, for all 3 of these patches, can you please resend them with the git
commit id of the original patch that is in Linus's tree? I need that to
be able to apply them to the stable releases.

thanks,

greg k-h

2010-11-11 14:15:52

by Joerg Roedel

[permalink] [raw]
Subject: Re: [PATCH 2/3] x86, mm: Fix CONFIG_VMSPLIT_1G and 2G_OPT trampoline

On Thu, Nov 11, 2010 at 09:13:58AM -0500, Greg KH wrote:
> On Thu, Nov 11, 2010 at 06:11:30AM -0800, Greg KH wrote:
> > On Thu, Nov 11, 2010 at 02:56:14PM +0100, Joerg Roedel wrote:
> > > From: Hugh Dickins <[email protected]>
> > >
> > > rc2 kernel crashes when booting second cpu on this CONFIG_VMSPLIT_2G_OPT
> > > laptop: whereas cloning from kernel to low mappings pgd range does need
> > > to limit by both KERNEL_PGD_PTRS and KERNEL_PGD_BOUNDARY, cloning kernel
> > > pgd range itself must not be limited by the smaller KERNEL_PGD_BOUNDARY.
> > >
> > > Signed-off-by: Hugh Dickins <[email protected]>
> > > LKML-Reference: <[email protected]>
> > > Signed-off-by: H. Peter Anvin <[email protected]>
> > > ---
> > > arch/x86/kernel/trampoline.c | 3 +--
> > > 1 files changed, 1 insertions(+), 2 deletions(-)
> >
> > Why are you sending this to me? I'm not the x86 maintainer.
>
> Ah, now it makes more sense (seeing 0/3 after 2/3 came in.)
>
> But, for all 3 of these patches, can you please resend them with the git
> commit id of the original patch that is in Linus's tree? I need that to
> be able to apply them to the stable releases.

Hey, you work very early in the morning :-)

I will add the upstream-commit-ids and repost.

Joerg

--
AMD Operating System Research Center

Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632

2010-11-11 15:14:24

by Joerg Roedel

[permalink] [raw]
Subject: [PATCH 0/3] Erratum 383 fix for 32 bit x86 kernels

Again with upstream commit-ids

2010-11-11 15:14:42

by Joerg Roedel

[permalink] [raw]
Subject: [PATCH 1/3] x86-32: Separate 1:1 pagetables from swapper_pg_dir

commit fd89a137924e0710078c3ae855e7cec1c43cb845 upstream

This patch fixes machine crashes which occur when heavily exercising the
CPU hotplug codepaths on a 32-bit kernel. These crashes are caused by
AMD Erratum 383 and result in a fatal machine check exception. Here's
the scenario:

1. On 32-bit, the swapper_pg_dir page table is used as the initial page
table for booting a secondary CPU.

2. To make this work, swapper_pg_dir needs a direct mapping of physical
memory in it (the low mappings). By adding those low, large page (2M)
mappings (PAE kernel), we create the necessary conditions for Erratum
383 to occur.

3. Other CPUs which do not participate in the off- and onlining game may
use swapper_pg_dir while the low mappings are present (when leave_mm is
called). For all steps below, the CPU referred to is a CPU that is using
swapper_pg_dir, and not the CPU which is being onlined.

4. The presence of the low mappings in swapper_pg_dir can result
in TLB entries for addresses below __PAGE_OFFSET to be established
speculatively. These TLB entries are marked global and large.

5. When the CPU with such TLB entry switches to another page table, this
TLB entry remains because it is global.

6. The process then generates an access to an address covered by the
above TLB entry but there is a permission mismatch - the TLB entry
covers a large global page not accessible to userspace.

7. Due to this permission mismatch a new 4kb, user TLB entry gets
established. Further, Erratum 383 provides for a small window of time
where both TLB entries are present. This results in an uncorrectable
machine check exception signalling a TLB multimatch which panics the
machine.

There are two ways to fix this issue:

1. Always do a global TLB flush when a new cr3 is loaded and the
old page table was swapper_pg_dir. I consider this a hack hard
to understand and with performance implications

2. Do not use swapper_pg_dir to boot secondary CPUs like 64-bit
does.

This patch implements solution 2. It introduces a trampoline_pg_dir
which has the same layout as swapper_pg_dir with low_mappings. This page
table is used as the initial page table of the booting CPU. Later in the
bringup process, it switches to swapper_pg_dir and does a global TLB
flush. This fixes the crashes in our test cases.

-v2: switch to swapper_pg_dir right after entering start_secondary() so
that we are able to access percpu data which might not be mapped in the
trampoline page table.

Signed-off-by: Joerg Roedel <[email protected]>
LKML-Reference: <20100816123833.GB28147@aftab>
Signed-off-by: Borislav Petkov <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
---
arch/x86/include/asm/pgtable_32.h | 1 +
arch/x86/include/asm/trampoline.h | 3 +++
arch/x86/kernel/head_32.S | 8 +++++++-
arch/x86/kernel/setup.c | 3 +++
arch/x86/kernel/smpboot.c | 32 +++++++++++++-------------------
arch/x86/kernel/trampoline.c | 18 ++++++++++++++++++
6 files changed, 45 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/pgtable_32.h b/arch/x86/include/asm/pgtable_32.h
index 01fd946..750f1bf 100644
--- a/arch/x86/include/asm/pgtable_32.h
+++ b/arch/x86/include/asm/pgtable_32.h
@@ -27,6 +27,7 @@ struct mm_struct;
struct vm_area_struct;

extern pgd_t swapper_pg_dir[1024];
+extern pgd_t trampoline_pg_dir[1024];

static inline void pgtable_cache_init(void) { }
static inline void check_pgt_cache(void) { }
diff --git a/arch/x86/include/asm/trampoline.h b/arch/x86/include/asm/trampoline.h
index 90f06c2..2ab4ccd 100644
--- a/arch/x86/include/asm/trampoline.h
+++ b/arch/x86/include/asm/trampoline.h
@@ -13,15 +13,18 @@ extern unsigned char *trampoline_base;

extern unsigned long init_rsp;
extern unsigned long initial_code;
+extern unsigned long initial_page_table;
extern unsigned long initial_gs;

#define TRAMPOLINE_SIZE roundup(trampoline_end - trampoline_data, PAGE_SIZE)
#define TRAMPOLINE_BASE 0x6000

extern unsigned long setup_trampoline(void);
+extern void __init setup_trampoline_page_table(void);
extern void __init reserve_trampoline_memory(void);
#else
static inline void reserve_trampoline_memory(void) {};
+extern void __init setup_trampoline_page_table(void) {};
#endif /* CONFIG_X86_TRAMPOLINE */

#endif /* __ASSEMBLY__ */
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 050c278..34c3308 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -324,7 +324,7 @@ ENTRY(startup_32_smp)
/*
* Enable paging
*/
- movl $pa(swapper_pg_dir),%eax
+ movl pa(initial_page_table), %eax
movl %eax,%cr3 /* set the page table pointer.. */
movl %cr0,%eax
orl $X86_CR0_PG,%eax
@@ -604,6 +604,8 @@ ignore_int:
.align 4
ENTRY(initial_code)
.long i386_start_kernel
+ENTRY(initial_page_table)
+ .long pa(swapper_pg_dir)

/*
* BSS section
@@ -619,6 +621,10 @@ ENTRY(swapper_pg_dir)
#endif
swapper_pg_fixmap:
.fill 1024,4,0
+#ifdef CONFIG_X86_TRAMPOLINE
+ENTRY(trampoline_pg_dir)
+ .fill 1024,4,0
+#endif
ENTRY(empty_zero_page)
.fill 4096,1,0

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index d7a0888..5449a26 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -110,6 +110,7 @@
#include <asm/numa_64.h>
#endif
#include <asm/mce.h>
+#include <asm/trampoline.h>

/*
* end_pfn only includes RAM, while max_pfn_mapped includes all e820 entries.
@@ -998,6 +999,8 @@ void __init setup_arch(char **cmdline_p)
paging_init();
x86_init.paging.pagetable_setup_done(swapper_pg_dir);

+ setup_trampoline_page_table();
+
tboot_probe();

#ifdef CONFIG_X86_64
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 29ec560..7e8e905 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -70,7 +70,6 @@

#ifdef CONFIG_X86_32
u8 apicid_2_node[MAX_APICID];
-static int low_mappings;
#endif

/* State of each CPU */
@@ -292,6 +291,18 @@ notrace static void __cpuinit start_secondary(void *unused)
* fragile that we want to limit the things done here to the
* most necessary things.
*/
+
+#ifdef CONFIG_X86_32
+ /*
+ * Switch away from the trampoline page-table
+ *
+ * Do this before cpu_init() because it needs to access per-cpu
+ * data which may not be mapped in the trampoline page-table.
+ */
+ load_cr3(swapper_pg_dir);
+ __flush_tlb_all();
+#endif
+
vmi_bringup();
cpu_init();
preempt_disable();
@@ -310,12 +321,6 @@ notrace static void __cpuinit start_secondary(void *unused)
enable_8259A_irq(0);
}

-#ifdef CONFIG_X86_32
- while (low_mappings)
- cpu_relax();
- __flush_tlb_all();
-#endif
-
/* This must be done before setting cpu_online_mask */
set_cpu_sibling_map(raw_smp_processor_id());
wmb();
@@ -741,6 +746,7 @@ do_rest:
#ifdef CONFIG_X86_32
/* Stack for startup_32 can be just as for start_secondary onwards */
irq_ctx_init(cpu);
+ initial_page_table = __pa(&trampoline_pg_dir);
#else
clear_tsk_thread_flag(c_idle.idle, TIF_FORK);
initial_gs = per_cpu_offset(cpu);
@@ -885,20 +891,8 @@ int __cpuinit native_cpu_up(unsigned int cpu)

per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;

-#ifdef CONFIG_X86_32
- /* init low mem mapping */
- clone_pgd_range(swapper_pg_dir, swapper_pg_dir + KERNEL_PGD_BOUNDARY,
- min_t(unsigned long, KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY));
- flush_tlb_all();
- low_mappings = 1;
-
err = do_boot_cpu(apicid, cpu);

- zap_low_mappings(false);
- low_mappings = 0;
-#else
- err = do_boot_cpu(apicid, cpu);
-#endif
if (err) {
pr_debug("do_boot_cpu failed %d\n", err);
return -EIO;
diff --git a/arch/x86/kernel/trampoline.c b/arch/x86/kernel/trampoline.c
index cd02212..4e816a4 100644
--- a/arch/x86/kernel/trampoline.c
+++ b/arch/x86/kernel/trampoline.c
@@ -1,6 +1,7 @@
#include <linux/io.h>

#include <asm/trampoline.h>
+#include <asm/pgtable.h>
#include <asm/e820.h>

#if defined(CONFIG_X86_64) && defined(CONFIG_ACPI_SLEEP)
@@ -39,3 +40,20 @@ unsigned long __trampinit setup_trampoline(void)
memcpy(trampoline_base, trampoline_data, TRAMPOLINE_SIZE);
return virt_to_phys(trampoline_base);
}
+
+void __init setup_trampoline_page_table(void)
+{
+#ifdef CONFIG_X86_32
+ /* Copy kernel address range */
+ clone_pgd_range(trampoline_pg_dir + KERNEL_PGD_BOUNDARY,
+ swapper_pg_dir + KERNEL_PGD_BOUNDARY,
+ min_t(unsigned long, KERNEL_PGD_PTRS,
+ KERNEL_PGD_BOUNDARY));
+
+ /* Initialize low mappings */
+ clone_pgd_range(trampoline_pg_dir,
+ swapper_pg_dir + KERNEL_PGD_BOUNDARY,
+ min_t(unsigned long, KERNEL_PGD_PTRS,
+ KERNEL_PGD_BOUNDARY));
+#endif
+}
--
1.7.0.4

2010-11-11 15:14:45

by Joerg Roedel

[permalink] [raw]
Subject: [PATCH 2/3] x86, mm: Fix CONFIG_VMSPLIT_1G and 2G_OPT trampoline

From: Hugh Dickins <[email protected]>

commit b7d460897739e02f186425b7276e3fdb1595cea7 upstream

rc2 kernel crashes when booting second cpu on this CONFIG_VMSPLIT_2G_OPT
laptop: whereas cloning from kernel to low mappings pgd range does need
to limit by both KERNEL_PGD_PTRS and KERNEL_PGD_BOUNDARY, cloning kernel
pgd range itself must not be limited by the smaller KERNEL_PGD_BOUNDARY.

Signed-off-by: Hugh Dickins <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
---
arch/x86/kernel/trampoline.c | 3 +--
1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/trampoline.c b/arch/x86/kernel/trampoline.c
index 4e816a4..0ac23a7 100644
--- a/arch/x86/kernel/trampoline.c
+++ b/arch/x86/kernel/trampoline.c
@@ -47,8 +47,7 @@ void __init setup_trampoline_page_table(void)
/* Copy kernel address range */
clone_pgd_range(trampoline_pg_dir + KERNEL_PGD_BOUNDARY,
swapper_pg_dir + KERNEL_PGD_BOUNDARY,
- min_t(unsigned long, KERNEL_PGD_PTRS,
- KERNEL_PGD_BOUNDARY));
+ KERNEL_PGD_PTRS);

/* Initialize low mappings */
clone_pgd_range(trampoline_pg_dir,
--
1.7.0.4

2010-11-11 15:14:26

by Joerg Roedel

[permalink] [raw]
Subject: [PATCH 3/3] x86-32: Fix dummy trampoline-related inline stubs

From: H. Peter Anvin <[email protected]>

commit 8848a91068c018bc91f597038a0f41462a0f88a4 upstream

Fix dummy inline stubs for trampoline-related functions when no
trampolines exist (until we get rid of the no-trampoline case
entirely.)

Signed-off-by: H. Peter Anvin <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Borislav Petkov <[email protected]>
LKML-Reference: <[email protected]>
---
arch/x86/include/asm/trampoline.h | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/trampoline.h b/arch/x86/include/asm/trampoline.h
index 2ab4ccd..ebace68 100644
--- a/arch/x86/include/asm/trampoline.h
+++ b/arch/x86/include/asm/trampoline.h
@@ -23,8 +23,8 @@ extern unsigned long setup_trampoline(void);
extern void __init setup_trampoline_page_table(void);
extern void __init reserve_trampoline_memory(void);
#else
-static inline void reserve_trampoline_memory(void) {};
-extern void __init setup_trampoline_page_table(void) {};
+static inline void setup_trampoline_page_table(void) {}
+static inline void reserve_trampoline_memory(void) {}
#endif /* CONFIG_X86_TRAMPOLINE */

#endif /* __ASSEMBLY__ */
--
1.7.0.4

2010-12-07 21:33:24

by Greg KH

[permalink] [raw]
Subject: Re: [PATCH 1/3] x86-32: Separate 1:1 pagetables from swapper_pg_dir

On Thu, Nov 11, 2010 at 04:16:14PM +0100, Joerg Roedel wrote:
> commit fd89a137924e0710078c3ae855e7cec1c43cb845 upstream

applied, thanks.

greg k-h

2010-12-07 21:33:22

by Greg KH

[permalink] [raw]
Subject: Re: [PATCH 3/3] x86-32: Fix dummy trampoline-related inline stubs

On Thu, Nov 11, 2010 at 04:16:16PM +0100, Joerg Roedel wrote:
> From: H. Peter Anvin <[email protected]>
>
> commit 8848a91068c018bc91f597038a0f41462a0f88a4 upstream

Applied, thanks.

greg k-h

2010-12-07 21:33:23

by Greg KH

[permalink] [raw]
Subject: Re: [stable] [PATCH 2/3] x86, mm: Fix CONFIG_VMSPLIT_1G and 2G_OPT trampoline

On Thu, Nov 11, 2010 at 04:16:15PM +0100, Joerg Roedel wrote:
> From: Hugh Dickins <[email protected]>
>
> commit b7d460897739e02f186425b7276e3fdb1595cea7 upstream

Applied, thanks.

greg k-h

2010-12-08 03:06:34

by Jeremy Fitzhardinge

[permalink] [raw]
Subject: Re: [PATCH 1/3] x86-32: Separate 1:1 pagetables from swapper_pg_dir

On 12/07/2010 01:05 PM, Greg KH wrote:
> On Thu, Nov 11, 2010 at 04:16:14PM +0100, Joerg Roedel wrote:
>> commit fd89a137924e0710078c3ae855e7cec1c43cb845 upstream
> applied, thanks.

This will need as well 5b5c1af104ab5adec1be9dcb4c787492d83d8d83 to
prevent Xen regressions.

J

2010-12-08 04:18:41

by Greg KH

[permalink] [raw]
Subject: Re: [PATCH 1/3] x86-32: Separate 1:1 pagetables from swapper_pg_dir

On Tue, Dec 07, 2010 at 07:06:31PM -0800, Jeremy Fitzhardinge wrote:
> On 12/07/2010 01:05 PM, Greg KH wrote:
> > On Thu, Nov 11, 2010 at 04:16:14PM +0100, Joerg Roedel wrote:
> >> commit fd89a137924e0710078c3ae855e7cec1c43cb845 upstream
> > applied, thanks.
>
> This will need as well 5b5c1af104ab5adec1be9dcb4c787492d83d8d83 to
> prevent Xen regressions.

So should I add that to a specific release? The next .36 stable or
something else?

confused,

greg k-h

2010-12-08 09:34:22

by Ian Campbell

[permalink] [raw]
Subject: Re: [PATCH 1/3] x86-32: Separate 1:1 pagetables from swapper_pg_dir

On Wed, 2010-12-08 at 04:15 +0000, Greg KH wrote:
> On Tue, Dec 07, 2010 at 07:06:31PM -0800, Jeremy Fitzhardinge wrote:
> > On 12/07/2010 01:05 PM, Greg KH wrote:
> > > On Thu, Nov 11, 2010 at 04:16:14PM +0100, Joerg Roedel wrote:
> > >> commit fd89a137924e0710078c3ae855e7cec1c43cb845 upstream
> > > applied, thanks.
> >
> > This will need as well 5b5c1af104ab5adec1be9dcb4c787492d83d8d83 to
> > prevent Xen regressions.
>
> So should I add that to a specific release? The next .36 stable or something else?

5b5c1af104ab5 fixed an issue exposed by b40827fa7268. I'm not sure if
fd89a13792 also exposes a similar issue, but I think it does not:

It looks to me like fd89a13792 only reads from swapper_pg_dir and writes
to trampoline_pg_dir which is unpinned (and unused) under Xen and hence
there is no problem and 5b5c1af104ab5 is not needed.

b40827fa7268 is in 2.6.37-rc and doesn't seem to be targeted for a
stable backport AFAICT.

Ian.

2010-12-08 11:59:16

by Borislav Petkov

[permalink] [raw]
Subject: Re: [PATCH 1/3] x86-32: Separate 1:1 pagetables from swapper_pg_dir

On Wed, Dec 08, 2010 at 04:34:15AM -0500, Ian Campbell wrote:
> On Wed, 2010-12-08 at 04:15 +0000, Greg KH wrote:
> > On Tue, Dec 07, 2010 at 07:06:31PM -0800, Jeremy Fitzhardinge wrote:
> > > On 12/07/2010 01:05 PM, Greg KH wrote:
> > > > On Thu, Nov 11, 2010 at 04:16:14PM +0100, Joerg Roedel wrote:
> > > >> commit fd89a137924e0710078c3ae855e7cec1c43cb845 upstream
> > > > applied, thanks.
> > >
> > > This will need as well 5b5c1af104ab5adec1be9dcb4c787492d83d8d83 to
> > > prevent Xen regressions.
> >
> > So should I add that to a specific release? The next .36 stable or something else?
>
> 5b5c1af104ab5 fixed an issue exposed by b40827fa7268. I'm not sure if
> fd89a13792 also exposes a similar issue, but I think it does not:
>
> It looks to me like fd89a13792 only reads from swapper_pg_dir and writes
> to trampoline_pg_dir which is unpinned (and unused) under Xen and hence
> there is no problem and 5b5c1af104ab5 is not needed.

I tend to agree with Ian's assessment here.

Let me put it this way: have you guys seen any Xen-related regressions
with fd89a13792? I mean, this patch went in after 2.6.36-rc1 and if
it were breaking Xen, we (or maybe you :)) would've caught it by now,
right?

> b40827fa7268 is in 2.6.37-rc and doesn't seem to be targeted for a
> stable backport AFAICT.

Nope, since it's not fixing a bug or fits any other of the stable rules.

--
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
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2010-12-08 15:21:54

by Jeremy Fitzhardinge

[permalink] [raw]
Subject: Re: [PATCH 1/3] x86-32: Separate 1:1 pagetables from swapper_pg_dir

On 12/08/2010 03:58 AM, Borislav Petkov wrote:
> On Wed, Dec 08, 2010 at 04:34:15AM -0500, Ian Campbell wrote:
>> On Wed, 2010-12-08 at 04:15 +0000, Greg KH wrote:
>>> On Tue, Dec 07, 2010 at 07:06:31PM -0800, Jeremy Fitzhardinge wrote:
>>>> On 12/07/2010 01:05 PM, Greg KH wrote:
>>>>> On Thu, Nov 11, 2010 at 04:16:14PM +0100, Joerg Roedel wrote:
>>>>>> commit fd89a137924e0710078c3ae855e7cec1c43cb845 upstream
>>>>> applied, thanks.
>>>> This will need as well 5b5c1af104ab5adec1be9dcb4c787492d83d8d83 to
>>>> prevent Xen regressions.
>>> So should I add that to a specific release? The next .36 stable or something else?
>> 5b5c1af104ab5 fixed an issue exposed by b40827fa7268. I'm not sure if
>> fd89a13792 also exposes a similar issue, but I think it does not:
>>
>> It looks to me like fd89a13792 only reads from swapper_pg_dir and writes
>> to trampoline_pg_dir which is unpinned (and unused) under Xen and hence
>> there is no problem and 5b5c1af104ab5 is not needed.
> I tend to agree with Ian's assessment here.
>
> Let me put it this way: have you guys seen any Xen-related regressions
> with fd89a13792? I mean, this patch went in after 2.6.36-rc1 and if
> it were breaking Xen, we (or maybe you :)) would've caught it by now,
> right?

No, I got confused. Sorry for spreading the confusion around...

J