[PATCH] arm/arm64: xen: Fix to convert percpu address to gfn correctly

Masami Hiramatsu posted 1 patch 3 weeks ago
Failed in applying to current master (apply log)
arch/arm/xen/enlighten.c |    2 +-
include/xen/arm/page.h   |    3 +++
2 files changed, 4 insertions(+), 1 deletion(-)

[PATCH] arm/arm64: xen: Fix to convert percpu address to gfn correctly

Posted by Masami Hiramatsu 3 weeks ago
Use per_cpu_ptr_to_phys() instead of virt_to_phys() for per-cpu
address conversion.

In xen_starting_cpu(), per-cpu xen_vcpu_info address is converted
to gfn by virt_to_gfn() macro. However, since the virt_to_gfn(v)
assumes the given virtual address is in contiguous kernel memory
area, it can not convert the per-cpu memory if it is allocated on
vmalloc area (depends on CONFIG_SMP).

Without this fix, the Dom0 kernel will fail to boot with following
errors.

[    0.466172] Xen: initializing cpu0
[    0.469601] ------------[ cut here ]------------
[    0.474295] WARNING: CPU: 0 PID: 1 at arch/arm64/xen/../../arm/xen/enlighten.c:153 xen_starting_cpu+0x160/0x180
[    0.484435] Modules linked in:
[    0.487565] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc4+ #4
[    0.493895] Hardware name: Socionext Developer Box (DT)
[    0.499194] pstate: 00000005 (nzcv daif -PAN -UAO BTYPE=--)
[    0.504836] pc : xen_starting_cpu+0x160/0x180
[    0.509263] lr : xen_starting_cpu+0xb0/0x180
[    0.513599] sp : ffff8000116cbb60
[    0.516984] x29: ffff8000116cbb60 x28: ffff80000abec000
[    0.522366] x27: 0000000000000000 x26: 0000000000000000
[    0.527754] x25: ffff80001156c000 x24: fffffdffbfcdb600
[    0.533129] x23: 0000000000000000 x22: 0000000000000000
[    0.538511] x21: ffff8000113a99c8 x20: ffff800010fe4f68
[    0.543892] x19: ffff8000113a9988 x18: 0000000000000010
[    0.549274] x17: 0000000094fe0f81 x16: 00000000deadbeef
[    0.554655] x15: ffffffffffffffff x14: 0720072007200720
[    0.560037] x13: 0720072007200720 x12: 0720072007200720
[    0.565418] x11: 0720072007200720 x10: 0720072007200720
[    0.570801] x9 : ffff8000100fbdc0 x8 : ffff800010715208
[    0.576182] x7 : 0000000000000054 x6 : ffff00001b790f00
[    0.581564] x5 : ffff800010bbf880 x4 : 0000000000000000
[    0.586945] x3 : 0000000000000000 x2 : ffff80000abec000
[    0.592327] x1 : 000000000000002f x0 : 0000800000000000
[    0.597716] Call trace:
[    0.600232]  xen_starting_cpu+0x160/0x180
[    0.604309]  cpuhp_invoke_callback+0xac/0x640
[    0.608736]  cpuhp_issue_call+0xf4/0x150
[    0.612728]  __cpuhp_setup_state_cpuslocked+0x128/0x2c8
[    0.618030]  __cpuhp_setup_state+0x84/0xf8
[    0.622192]  xen_guest_init+0x324/0x364
[    0.626097]  do_one_initcall+0x54/0x250
[    0.630003]  kernel_init_freeable+0x12c/0x2c8
[    0.634428]  kernel_init+0x1c/0x128
[    0.637988]  ret_from_fork+0x10/0x18
[    0.641635] ---[ end trace d95b5309a33f8b27 ]---
[    0.646337] ------------[ cut here ]------------
[    0.651005] kernel BUG at arch/arm64/xen/../../arm/xen/enlighten.c:158!
[    0.657697] Internal error: Oops - BUG: 0 [#1] SMP
[    0.662548] Modules linked in:
[    0.665676] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W         5.9.0-rc4+ #4
[    0.673398] Hardware name: Socionext Developer Box (DT)
[    0.678695] pstate: 00000005 (nzcv daif -PAN -UAO BTYPE=--)
[    0.684338] pc : xen_starting_cpu+0x178/0x180
[    0.688765] lr : xen_starting_cpu+0x144/0x180
[    0.693188] sp : ffff8000116cbb60
[    0.696573] x29: ffff8000116cbb60 x28: ffff80000abec000
[    0.701955] x27: 0000000000000000 x26: 0000000000000000
[    0.707344] x25: ffff80001156c000 x24: fffffdffbfcdb600
[    0.712718] x23: 0000000000000000 x22: 0000000000000000
[    0.718107] x21: ffff8000113a99c8 x20: ffff800010fe4f68
[    0.723481] x19: ffff8000113a9988 x18: 0000000000000010
[    0.728863] x17: 0000000094fe0f81 x16: 00000000deadbeef
[    0.734245] x15: ffffffffffffffff x14: 0720072007200720
[    0.739626] x13: 0720072007200720 x12: 0720072007200720
[    0.745008] x11: 0720072007200720 x10: 0720072007200720
[    0.750390] x9 : ffff8000100fbdc0 x8 : ffff800010715208
[    0.755771] x7 : 0000000000000054 x6 : ffff00001b790f00
[    0.761153] x5 : ffff800010bbf880 x4 : 0000000000000000
[    0.766534] x3 : 0000000000000000 x2 : 00000000deadbeef
[    0.771916] x1 : 00000000deadbeef x0 : ffffffffffffffea
[    0.777304] Call trace:
[    0.779819]  xen_starting_cpu+0x178/0x180
[    0.783898]  cpuhp_invoke_callback+0xac/0x640
[    0.788325]  cpuhp_issue_call+0xf4/0x150
[    0.792317]  __cpuhp_setup_state_cpuslocked+0x128/0x2c8
[    0.797619]  __cpuhp_setup_state+0x84/0xf8
[    0.801779]  xen_guest_init+0x324/0x364
[    0.805683]  do_one_initcall+0x54/0x250
[    0.809590]  kernel_init_freeable+0x12c/0x2c8
[    0.814016]  kernel_init+0x1c/0x128
[    0.817583]  ret_from_fork+0x10/0x18
[    0.821226] Code: d0006980 f9427c00 cb000300 17ffffea (d4210000)
[    0.827415] ---[ end trace d95b5309a33f8b28 ]---
[    0.832076] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
[    0.839815] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---

Fixes: 250c9af3d831 ("arm/xen: Add support for 64KB page granularity")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 arch/arm/xen/enlighten.c |    2 +-
 include/xen/arm/page.h   |    3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index e93145d72c26..a6ab3689b2f4 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -150,7 +150,7 @@ static int xen_starting_cpu(unsigned int cpu)
 	pr_info("Xen: initializing cpu%d\n", cpu);
 	vcpup = per_cpu_ptr(xen_vcpu_info, cpu);
 
-	info.mfn = virt_to_gfn(vcpup);
+	info.mfn = percpu_to_gfn(vcpup);
 	info.offset = xen_offset_in_page(vcpup);
 
 	err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, xen_vcpu_nr(cpu),
diff --git a/include/xen/arm/page.h b/include/xen/arm/page.h
index 39df751d0dc4..ac1b65470563 100644
--- a/include/xen/arm/page.h
+++ b/include/xen/arm/page.h
@@ -83,6 +83,9 @@ static inline unsigned long bfn_to_pfn(unsigned long bfn)
 	})
 #define gfn_to_virt(m)		(__va(gfn_to_pfn(m) << XEN_PAGE_SHIFT))
 
+#define percpu_to_gfn(v)	\
+	(pfn_to_gfn(per_cpu_ptr_to_phys(v) >> XEN_PAGE_SHIFT))
+
 /* Only used in PV code. But ARM guests are always HVM. */
 static inline xmaddr_t arbitrary_virt_to_machine(void *vaddr)
 {


Re: [PATCH] arm/arm64: xen: Fix to convert percpu address to gfn correctly

Posted by Julien Grall 3 weeks ago
Hi Masami,

On 05/10/2020 14:39, Masami Hiramatsu wrote:
> Use per_cpu_ptr_to_phys() instead of virt_to_phys() for per-cpu
> address conversion.
> 
> In xen_starting_cpu(), per-cpu xen_vcpu_info address is converted
> to gfn by virt_to_gfn() macro. However, since the virt_to_gfn(v)
> assumes the given virtual address is in contiguous kernel memory
> area, it can not convert the per-cpu memory if it is allocated on
> vmalloc area (depends on CONFIG_SMP).

Are you sure about this? I have a .config with CONFIG_SMP=y where the 
per-cpu region for CPU0 is allocated outside of vmalloc area.

However, I was able to trigger the bug as soon as CONFIG_NUMA_BALANCING 
was enabled.

[...]

> Fixes: 250c9af3d831 ("arm/xen: Add support for 64KB page granularity")

FWIW, I think the bug was already present before 250c9af3d831.

> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>   arch/arm/xen/enlighten.c |    2 +-
>   include/xen/arm/page.h   |    3 +++
>   2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index e93145d72c26..a6ab3689b2f4 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -150,7 +150,7 @@ static int xen_starting_cpu(unsigned int cpu)
>   	pr_info("Xen: initializing cpu%d\n", cpu);
>   	vcpup = per_cpu_ptr(xen_vcpu_info, cpu);
>   
> -	info.mfn = virt_to_gfn(vcpup);
> +	info.mfn = percpu_to_gfn(vcpup);
>   	info.offset = xen_offset_in_page(vcpup);
>   
>   	err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, xen_vcpu_nr(cpu),
> diff --git a/include/xen/arm/page.h b/include/xen/arm/page.h
> index 39df751d0dc4..ac1b65470563 100644
> --- a/include/xen/arm/page.h
> +++ b/include/xen/arm/page.h
> @@ -83,6 +83,9 @@ static inline unsigned long bfn_to_pfn(unsigned long bfn)
>   	})
>   #define gfn_to_virt(m)		(__va(gfn_to_pfn(m) << XEN_PAGE_SHIFT))
>   
> +#define percpu_to_gfn(v)	\
> +	(pfn_to_gfn(per_cpu_ptr_to_phys(v) >> XEN_PAGE_SHIFT))
> +
>   /* Only used in PV code. But ARM guests are always HVM. */
>   static inline xmaddr_t arbitrary_virt_to_machine(void *vaddr)
>   {
> 

Cheers,

-- 
Julien Grall

Re: [PATCH] arm/arm64: xen: Fix to convert percpu address to gfn correctly

Posted by Stefano Stabellini 3 weeks ago
On Mon, 5 Oct 2020, Julien Grall wrote:
> Hi Masami,
> 
> On 05/10/2020 14:39, Masami Hiramatsu wrote:
> > Use per_cpu_ptr_to_phys() instead of virt_to_phys() for per-cpu
> > address conversion.
> > 
> > In xen_starting_cpu(), per-cpu xen_vcpu_info address is converted
> > to gfn by virt_to_gfn() macro. However, since the virt_to_gfn(v)
> > assumes the given virtual address is in contiguous kernel memory
> > area, it can not convert the per-cpu memory if it is allocated on
> > vmalloc area (depends on CONFIG_SMP).
> 
> Are you sure about this? I have a .config with CONFIG_SMP=y where the per-cpu
> region for CPU0 is allocated outside of vmalloc area.
> 
> However, I was able to trigger the bug as soon as CONFIG_NUMA_BALANCING was
> enabled.

I cannot reproduce the issue with defconfig, but I can with Masami's
kconfig.

If I disable just CONFIG_NUMA_BALANCING from Masami's kconfig, the
problem still appears.

If I disable CONFIG_NUMA from Masami's kconfig, it works, which is
strange because CONFIG_NUMA is enabled in defconfig, and defconfig
works.


> [...]
> 
> > Fixes: 250c9af3d831 ("arm/xen: Add support for 64KB page granularity")
> 
> FWIW, I think the bug was already present before 250c9af3d831.

Yeah, I bet 250c9af3d831 is not what introduced the issue. Whatever
caused virt_to_phys to stop working on vmalloc'ed addresses is the cause
of the problem. It is something that went in 5.9 (5.8 works) but I don't
know what for sure.


> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > ---
> >   arch/arm/xen/enlighten.c |    2 +-
> >   include/xen/arm/page.h   |    3 +++
> >   2 files changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> > index e93145d72c26..a6ab3689b2f4 100644
> > --- a/arch/arm/xen/enlighten.c
> > +++ b/arch/arm/xen/enlighten.c
> > @@ -150,7 +150,7 @@ static int xen_starting_cpu(unsigned int cpu)
> >   	pr_info("Xen: initializing cpu%d\n", cpu);
> >   	vcpup = per_cpu_ptr(xen_vcpu_info, cpu);
> >   -	info.mfn = virt_to_gfn(vcpup);
> > +	info.mfn = percpu_to_gfn(vcpup);
> >   	info.offset = xen_offset_in_page(vcpup);
> >     	err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, xen_vcpu_nr(cpu),
> > diff --git a/include/xen/arm/page.h b/include/xen/arm/page.h
> > index 39df751d0dc4..ac1b65470563 100644
> > --- a/include/xen/arm/page.h
> > +++ b/include/xen/arm/page.h
> > @@ -83,6 +83,9 @@ static inline unsigned long bfn_to_pfn(unsigned long bfn)
> >   	})
> >   #define gfn_to_virt(m)		(__va(gfn_to_pfn(m) <<
> > XEN_PAGE_SHIFT))
> >   +#define percpu_to_gfn(v)	\
> > +	(pfn_to_gfn(per_cpu_ptr_to_phys(v) >> XEN_PAGE_SHIFT))
> > +
> >   /* Only used in PV code. But ARM guests are always HVM. */
> >   static inline xmaddr_t arbitrary_virt_to_machine(void *vaddr)
> >   {


The fix is fine for me. I tested it and it works. We need to remove the
"Fixes:" line from the commit message. Ideally, replacing it with a
reference to what is the source of the problem.

Aside from that:

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

Re: [PATCH] arm/arm64: xen: Fix to convert percpu address to gfn correctly

Posted by Masami Hiramatsu 3 weeks ago
On Mon, 5 Oct 2020 18:13:22 -0700 (PDT)
Stefano Stabellini <sstabellini@kernel.org> wrote:

> On Mon, 5 Oct 2020, Julien Grall wrote:
> > Hi Masami,
> > 
> > On 05/10/2020 14:39, Masami Hiramatsu wrote:
> > > Use per_cpu_ptr_to_phys() instead of virt_to_phys() for per-cpu
> > > address conversion.
> > > 
> > > In xen_starting_cpu(), per-cpu xen_vcpu_info address is converted
> > > to gfn by virt_to_gfn() macro. However, since the virt_to_gfn(v)
> > > assumes the given virtual address is in contiguous kernel memory
> > > area, it can not convert the per-cpu memory if it is allocated on
> > > vmalloc area (depends on CONFIG_SMP).
> > 
> > Are you sure about this? I have a .config with CONFIG_SMP=y where the per-cpu
> > region for CPU0 is allocated outside of vmalloc area.
> > 
> > However, I was able to trigger the bug as soon as CONFIG_NUMA_BALANCING was
> > enabled.
> 
> I cannot reproduce the issue with defconfig, but I can with Masami's
> kconfig.
> 
> If I disable just CONFIG_NUMA_BALANCING from Masami's kconfig, the
> problem still appears.
> 
> If I disable CONFIG_NUMA from Masami's kconfig, it works, which is
> strange because CONFIG_NUMA is enabled in defconfig, and defconfig
> works.

Hmm, strange, because when I disabled CONFIG_NUMA_BALANCING, the issue
disappeared.

--- config-5.9.0-rc4+   2020-10-06 11:36:20.620107129 +0900
+++ config-5.9.0-rc4+.buggy     2020-10-05 21:04:40.369936461 +0900
@@ -131,7 +131,8 @@
 CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y
 CONFIG_CC_HAS_INT128=y
 CONFIG_ARCH_SUPPORTS_INT128=y
-# CONFIG_NUMA_BALANCING is not set
+CONFIG_NUMA_BALANCING=y
+CONFIG_NUMA_BALANCING_DEFAULT_ENABLED=y
 CONFIG_CGROUPS=y
 CONFIG_PAGE_COUNTER=y
 CONFIG_MEMCG=y

So buggy config just enabled NUMA_BALANCING (and default enabled)

> > [...]
> > 
> > > Fixes: 250c9af3d831 ("arm/xen: Add support for 64KB page granularity")
> > 
> > FWIW, I think the bug was already present before 250c9af3d831.
> 
> Yeah, I bet 250c9af3d831 is not what introduced the issue. Whatever
> caused virt_to_phys to stop working on vmalloc'ed addresses is the cause
> of the problem. It is something that went in 5.9 (5.8 works) but I don't
> know what for sure.

OK.

> 
> 
> > > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > > ---
> > >   arch/arm/xen/enlighten.c |    2 +-
> > >   include/xen/arm/page.h   |    3 +++
> > >   2 files changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> > > index e93145d72c26..a6ab3689b2f4 100644
> > > --- a/arch/arm/xen/enlighten.c
> > > +++ b/arch/arm/xen/enlighten.c
> > > @@ -150,7 +150,7 @@ static int xen_starting_cpu(unsigned int cpu)
> > >   	pr_info("Xen: initializing cpu%d\n", cpu);
> > >   	vcpup = per_cpu_ptr(xen_vcpu_info, cpu);
> > >   -	info.mfn = virt_to_gfn(vcpup);
> > > +	info.mfn = percpu_to_gfn(vcpup);
> > >   	info.offset = xen_offset_in_page(vcpup);
> > >     	err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, xen_vcpu_nr(cpu),
> > > diff --git a/include/xen/arm/page.h b/include/xen/arm/page.h
> > > index 39df751d0dc4..ac1b65470563 100644
> > > --- a/include/xen/arm/page.h
> > > +++ b/include/xen/arm/page.h
> > > @@ -83,6 +83,9 @@ static inline unsigned long bfn_to_pfn(unsigned long bfn)
> > >   	})
> > >   #define gfn_to_virt(m)		(__va(gfn_to_pfn(m) <<
> > > XEN_PAGE_SHIFT))
> > >   +#define percpu_to_gfn(v)	\
> > > +	(pfn_to_gfn(per_cpu_ptr_to_phys(v) >> XEN_PAGE_SHIFT))
> > > +
> > >   /* Only used in PV code. But ARM guests are always HVM. */
> > >   static inline xmaddr_t arbitrary_virt_to_machine(void *vaddr)
> > >   {
> 
> 
> The fix is fine for me. I tested it and it works. We need to remove the
> "Fixes:" line from the commit message. Ideally, replacing it with a
> reference to what is the source of the problem.

OK, as I said, it seems commit 9a9ab3cc00dc ("xen/arm: SMP support") has
introduced the per-cpu code. So note it instead of Fixes tag.

> 
> Aside from that:
> 
> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

Thank you!

-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [PATCH] arm/arm64: xen: Fix to convert percpu address to gfn correctly

Posted by Stefano Stabellini 3 weeks ago
On Tue, 6 Oct 2020, Masami Hiramatsu wrote:
> On Mon, 5 Oct 2020 18:13:22 -0700 (PDT)
> Stefano Stabellini <sstabellini@kernel.org> wrote:
> 
> > On Mon, 5 Oct 2020, Julien Grall wrote:
> > > Hi Masami,
> > > 
> > > On 05/10/2020 14:39, Masami Hiramatsu wrote:
> > > > Use per_cpu_ptr_to_phys() instead of virt_to_phys() for per-cpu
> > > > address conversion.
> > > > 
> > > > In xen_starting_cpu(), per-cpu xen_vcpu_info address is converted
> > > > to gfn by virt_to_gfn() macro. However, since the virt_to_gfn(v)
> > > > assumes the given virtual address is in contiguous kernel memory
> > > > area, it can not convert the per-cpu memory if it is allocated on
> > > > vmalloc area (depends on CONFIG_SMP).
> > > 
> > > Are you sure about this? I have a .config with CONFIG_SMP=y where the per-cpu
> > > region for CPU0 is allocated outside of vmalloc area.
> > > 
> > > However, I was able to trigger the bug as soon as CONFIG_NUMA_BALANCING was
> > > enabled.
> > 
> > I cannot reproduce the issue with defconfig, but I can with Masami's
> > kconfig.
> > 
> > If I disable just CONFIG_NUMA_BALANCING from Masami's kconfig, the
> > problem still appears.
> > 
> > If I disable CONFIG_NUMA from Masami's kconfig, it works, which is
> > strange because CONFIG_NUMA is enabled in defconfig, and defconfig
> > works.
> 
> Hmm, strange, because when I disabled CONFIG_NUMA_BALANCING, the issue
> disappeared.
> 
> --- config-5.9.0-rc4+   2020-10-06 11:36:20.620107129 +0900
> +++ config-5.9.0-rc4+.buggy     2020-10-05 21:04:40.369936461 +0900
> @@ -131,7 +131,8 @@
>  CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y
>  CONFIG_CC_HAS_INT128=y
>  CONFIG_ARCH_SUPPORTS_INT128=y
> -# CONFIG_NUMA_BALANCING is not set
> +CONFIG_NUMA_BALANCING=y
> +CONFIG_NUMA_BALANCING_DEFAULT_ENABLED=y
>  CONFIG_CGROUPS=y
>  CONFIG_PAGE_COUNTER=y
>  CONFIG_MEMCG=y
> 
> So buggy config just enabled NUMA_BALANCING (and default enabled)

Yeah but both NUMA and NUMA_BALANCING are enabled in defconfig which
works fine...

[...]

> > The fix is fine for me. I tested it and it works. We need to remove the
> > "Fixes:" line from the commit message. Ideally, replacing it with a
> > reference to what is the source of the problem.
> 
> OK, as I said, it seems commit 9a9ab3cc00dc ("xen/arm: SMP support") has
> introduced the per-cpu code. So note it instead of Fixes tag.

...and commit 9a9ab3cc00dc was already present in 5.8 which also works
fine with your kconfig. Something else changed in 5.9 causing this
breakage as a side effect. Commit 9a9ab3cc00dc is there since 2013, I
think it is OK -- this patch is fixing something else.

Re: [PATCH] arm/arm64: xen: Fix to convert percpu address to gfn correctly

Posted by Masami Hiramatsu 3 weeks ago
On Tue, 6 Oct 2020 10:56:52 -0700 (PDT)
Stefano Stabellini <sstabellini@kernel.org> wrote:

> On Tue, 6 Oct 2020, Masami Hiramatsu wrote:
> > On Mon, 5 Oct 2020 18:13:22 -0700 (PDT)
> > Stefano Stabellini <sstabellini@kernel.org> wrote:
> > 
> > > On Mon, 5 Oct 2020, Julien Grall wrote:
> > > > Hi Masami,
> > > > 
> > > > On 05/10/2020 14:39, Masami Hiramatsu wrote:
> > > > > Use per_cpu_ptr_to_phys() instead of virt_to_phys() for per-cpu
> > > > > address conversion.
> > > > > 
> > > > > In xen_starting_cpu(), per-cpu xen_vcpu_info address is converted
> > > > > to gfn by virt_to_gfn() macro. However, since the virt_to_gfn(v)
> > > > > assumes the given virtual address is in contiguous kernel memory
> > > > > area, it can not convert the per-cpu memory if it is allocated on
> > > > > vmalloc area (depends on CONFIG_SMP).
> > > > 
> > > > Are you sure about this? I have a .config with CONFIG_SMP=y where the per-cpu
> > > > region for CPU0 is allocated outside of vmalloc area.
> > > > 
> > > > However, I was able to trigger the bug as soon as CONFIG_NUMA_BALANCING was
> > > > enabled.
> > > 
> > > I cannot reproduce the issue with defconfig, but I can with Masami's
> > > kconfig.
> > > 
> > > If I disable just CONFIG_NUMA_BALANCING from Masami's kconfig, the
> > > problem still appears.
> > > 
> > > If I disable CONFIG_NUMA from Masami's kconfig, it works, which is
> > > strange because CONFIG_NUMA is enabled in defconfig, and defconfig
> > > works.
> > 
> > Hmm, strange, because when I disabled CONFIG_NUMA_BALANCING, the issue
> > disappeared.
> > 
> > --- config-5.9.0-rc4+   2020-10-06 11:36:20.620107129 +0900
> > +++ config-5.9.0-rc4+.buggy     2020-10-05 21:04:40.369936461 +0900
> > @@ -131,7 +131,8 @@
> >  CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y
> >  CONFIG_CC_HAS_INT128=y
> >  CONFIG_ARCH_SUPPORTS_INT128=y
> > -# CONFIG_NUMA_BALANCING is not set
> > +CONFIG_NUMA_BALANCING=y
> > +CONFIG_NUMA_BALANCING_DEFAULT_ENABLED=y
> >  CONFIG_CGROUPS=y
> >  CONFIG_PAGE_COUNTER=y
> >  CONFIG_MEMCG=y
> > 
> > So buggy config just enabled NUMA_BALANCING (and default enabled)
> 
> Yeah but both NUMA and NUMA_BALANCING are enabled in defconfig which
> works fine...

Hmm, I found that the xen_vcpu_info was allocated on km if the Dom0 has
enough memory. On my environment, if Xen passed 2GB of RAM to Dom0, it
was allocated on kernel linear mapped address, but with 1GB of RAM, it
was on vmalloc area.
As far as I can see, it seems that the percpu allocates memory from
2nd chunk if the default memory size is small.

I've built a kernel with patch [1] and boot the same kernel up with
different dom0_mem option with "trace_event=percpu:*" kernel cmdline.
Then got following logs.

Boot with 4GB:
          <idle>-0     [000] ....     0.543208: percpu_create_chunk: base_addr=000000005d5ad71c
 [...]
         systemd-1     [000] ....     0.568931: percpu_alloc_percpu: reserved=0 is_atomic=0 size=48 align=8 base_addr=00000000fa92a086 off=32672 ptr=000000008da0b73d
         systemd-1     [000] ....     0.568938: xen_guest_init: Xen: alloc xen_vcpu_info ffff800011003fa0 id=000000008da0b73d
         systemd-1     [000] ....     0.586635: xen_starting_cpu: Xen: xen_vcpu_info ffff800011003fa0, vcpup ffff00092f4ebfa0 per_cpu_offset[0] ffff80091e4e8000

(NOTE: base_addr and ptr are encoded to the ids, not actual address
 because of "%p" printk format)

In this log, we can see the xen_vcpu_info is allocated NOT on the
new chunk (this is the 2nd chunk). As you can see, the vcpup is in
the kernel linear address in this case, because it came from the
1st kernel embedded chunk.


Boot with 1GB
          <idle>-0     [000] ....     0.516221: percpu_create_chunk: base_addr=000000008456b989
[...]
         systemd-1     [000] ....     0.541982: percpu_alloc_percpu: reserved=0 is_atomic=0 size=48 align=8 base_addr=000000008456b989 off=17920 ptr=00000000c247612d
         systemd-1     [000] ....     0.541989: xen_guest_init: Xen: alloc xen_vcpu_info 7dff951f0600 id=00000000c247612d
         systemd-1     [000] ....     0.559690: xen_starting_cpu: Xen: xen_vcpu_info 7dff951f0600, vcpup fffffdffbfcdc600 per_cpu_offset[0] ffff80002aaec000

On the other hand, when we boot the dom0 with 1GB memory, the xen_vcpu_info
is allocated on the new chunk (the id of base_addr is same).
Since the data of new chunk is allocated on vmalloc area, vcpup points
the vmalloc address.

So, the bug seems not to depend on the kconfig, but depends on where
the percpu memory is allocated from.

> [...]
> 
> > > The fix is fine for me. I tested it and it works. We need to remove the
> > > "Fixes:" line from the commit message. Ideally, replacing it with a
> > > reference to what is the source of the problem.
> > 
> > OK, as I said, it seems commit 9a9ab3cc00dc ("xen/arm: SMP support") has
> > introduced the per-cpu code. So note it instead of Fixes tag.
> 
> ...and commit 9a9ab3cc00dc was already present in 5.8 which also works
> fine with your kconfig. Something else changed in 5.9 causing this
> breakage as a side effect. Commit 9a9ab3cc00dc is there since 2013, I
> think it is OK -- this patch is fixing something else.

I think the commit 9a9ab3cc00dc theoletically wrong because it uses
__pa() on percpu address. But that is not guaranteed according to the
comment on per_cpu_ptr_to_phys() as below.

----
 * percpu allocator has special setup for the first chunk, which currently
 * supports either embedding in linear address space or vmalloc mapping,
 * and, from the second one, the backing allocator (currently either vm or
 * km) provides translation.
 *
 * The addr can be translated simply without checking if it falls into the
 * first chunk. But the current code reflects better how percpu allocator
 * actually works, and the verification can discover both bugs in percpu
 * allocator itself and per_cpu_ptr_to_phys() callers. So we keep current
 * code.
----

So we must use per_cpu_ptr_to_phys() instead of __pa() macro for percpu
address. That's why I pointed this will fix the commit 9a9ab3cc00dc.

Thank you,

[1]
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index a6ab3689b2f4..1786b8b51a60 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -149,6 +149,7 @@ static int xen_starting_cpu(unsigned int cpu)
 
 	pr_info("Xen: initializing cpu%d\n", cpu);
 	vcpup = per_cpu_ptr(xen_vcpu_info, cpu);
+	trace_printk("Xen: xen_vcpu_info %lx, vcpup %lx per_cpu_offset[%d] %lx\n", (unsigned long)xen_vcpu_info, (unsigned long)vcpup, cpu, per_cpu_offset(cpu));
 
 	info.mfn = percpu_to_gfn(vcpup);
 	info.offset = xen_offset_in_page(vcpup);
@@ -356,6 +357,7 @@ static int __init xen_guest_init(void)
 	xen_vcpu_info = alloc_percpu(struct vcpu_info);
 	if (xen_vcpu_info == NULL)
 		return -ENOMEM;
+	trace_printk("Xen: alloc xen_vcpu_info %lx id=%p\n", (unsigned long)xen_vcpu_info, xen_vcpu_info);
 
 	/* Direct vCPU id mapping for ARM guests. */
 	for_each_possible_cpu(cpu)

-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [PATCH] arm/arm64: xen: Fix to convert percpu address to gfn correctly

Posted by Stefano Stabellini 3 weeks ago
On Thu, 8 Oct 2020, Masami Hiramatsu wrote:
> On Tue, 6 Oct 2020 10:56:52 -0700 (PDT)
> Stefano Stabellini <sstabellini@kernel.org> wrote:
> 
> > On Tue, 6 Oct 2020, Masami Hiramatsu wrote:
> > > On Mon, 5 Oct 2020 18:13:22 -0700 (PDT)
> > > Stefano Stabellini <sstabellini@kernel.org> wrote:
> > > 
> > > > On Mon, 5 Oct 2020, Julien Grall wrote:
> > > > > Hi Masami,
> > > > > 
> > > > > On 05/10/2020 14:39, Masami Hiramatsu wrote:
> > > > > > Use per_cpu_ptr_to_phys() instead of virt_to_phys() for per-cpu
> > > > > > address conversion.
> > > > > > 
> > > > > > In xen_starting_cpu(), per-cpu xen_vcpu_info address is converted
> > > > > > to gfn by virt_to_gfn() macro. However, since the virt_to_gfn(v)
> > > > > > assumes the given virtual address is in contiguous kernel memory
> > > > > > area, it can not convert the per-cpu memory if it is allocated on
> > > > > > vmalloc area (depends on CONFIG_SMP).
> > > > > 
> > > > > Are you sure about this? I have a .config with CONFIG_SMP=y where the per-cpu
> > > > > region for CPU0 is allocated outside of vmalloc area.
> > > > > 
> > > > > However, I was able to trigger the bug as soon as CONFIG_NUMA_BALANCING was
> > > > > enabled.
> > > > 
> > > > I cannot reproduce the issue with defconfig, but I can with Masami's
> > > > kconfig.
> > > > 
> > > > If I disable just CONFIG_NUMA_BALANCING from Masami's kconfig, the
> > > > problem still appears.
> > > > 
> > > > If I disable CONFIG_NUMA from Masami's kconfig, it works, which is
> > > > strange because CONFIG_NUMA is enabled in defconfig, and defconfig
> > > > works.
> > > 
> > > Hmm, strange, because when I disabled CONFIG_NUMA_BALANCING, the issue
> > > disappeared.
> > > 
> > > --- config-5.9.0-rc4+   2020-10-06 11:36:20.620107129 +0900
> > > +++ config-5.9.0-rc4+.buggy     2020-10-05 21:04:40.369936461 +0900
> > > @@ -131,7 +131,8 @@
> > >  CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y
> > >  CONFIG_CC_HAS_INT128=y
> > >  CONFIG_ARCH_SUPPORTS_INT128=y
> > > -# CONFIG_NUMA_BALANCING is not set
> > > +CONFIG_NUMA_BALANCING=y
> > > +CONFIG_NUMA_BALANCING_DEFAULT_ENABLED=y
> > >  CONFIG_CGROUPS=y
> > >  CONFIG_PAGE_COUNTER=y
> > >  CONFIG_MEMCG=y
> > > 
> > > So buggy config just enabled NUMA_BALANCING (and default enabled)
> > 
> > Yeah but both NUMA and NUMA_BALANCING are enabled in defconfig which
> > works fine...
> 
> Hmm, I found that the xen_vcpu_info was allocated on km if the Dom0 has
> enough memory. On my environment, if Xen passed 2GB of RAM to Dom0, it
> was allocated on kernel linear mapped address, but with 1GB of RAM, it
> was on vmalloc area.
> As far as I can see, it seems that the percpu allocates memory from
> 2nd chunk if the default memory size is small.
> 
> I've built a kernel with patch [1] and boot the same kernel up with
> different dom0_mem option with "trace_event=percpu:*" kernel cmdline.
> Then got following logs.
> 
> Boot with 4GB:
>           <idle>-0     [000] ....     0.543208: percpu_create_chunk: base_addr=000000005d5ad71c
>  [...]
>          systemd-1     [000] ....     0.568931: percpu_alloc_percpu: reserved=0 is_atomic=0 size=48 align=8 base_addr=00000000fa92a086 off=32672 ptr=000000008da0b73d
>          systemd-1     [000] ....     0.568938: xen_guest_init: Xen: alloc xen_vcpu_info ffff800011003fa0 id=000000008da0b73d
>          systemd-1     [000] ....     0.586635: xen_starting_cpu: Xen: xen_vcpu_info ffff800011003fa0, vcpup ffff00092f4ebfa0 per_cpu_offset[0] ffff80091e4e8000
> 
> (NOTE: base_addr and ptr are encoded to the ids, not actual address
>  because of "%p" printk format)
> 
> In this log, we can see the xen_vcpu_info is allocated NOT on the
> new chunk (this is the 2nd chunk). As you can see, the vcpup is in
> the kernel linear address in this case, because it came from the
> 1st kernel embedded chunk.
> 
> 
> Boot with 1GB
>           <idle>-0     [000] ....     0.516221: percpu_create_chunk: base_addr=000000008456b989
> [...]
>          systemd-1     [000] ....     0.541982: percpu_alloc_percpu: reserved=0 is_atomic=0 size=48 align=8 base_addr=000000008456b989 off=17920 ptr=00000000c247612d
>          systemd-1     [000] ....     0.541989: xen_guest_init: Xen: alloc xen_vcpu_info 7dff951f0600 id=00000000c247612d
>          systemd-1     [000] ....     0.559690: xen_starting_cpu: Xen: xen_vcpu_info 7dff951f0600, vcpup fffffdffbfcdc600 per_cpu_offset[0] ffff80002aaec000
> 
> On the other hand, when we boot the dom0 with 1GB memory, the xen_vcpu_info
> is allocated on the new chunk (the id of base_addr is same).
> Since the data of new chunk is allocated on vmalloc area, vcpup points
> the vmalloc address.
> 
> So, the bug seems not to depend on the kconfig, but depends on where
> the percpu memory is allocated from.
> 
> > [...]
> > 
> > > > The fix is fine for me. I tested it and it works. We need to remove the
> > > > "Fixes:" line from the commit message. Ideally, replacing it with a
> > > > reference to what is the source of the problem.
> > > 
> > > OK, as I said, it seems commit 9a9ab3cc00dc ("xen/arm: SMP support") has
> > > introduced the per-cpu code. So note it instead of Fixes tag.
> > 
> > ...and commit 9a9ab3cc00dc was already present in 5.8 which also works
> > fine with your kconfig. Something else changed in 5.9 causing this
> > breakage as a side effect. Commit 9a9ab3cc00dc is there since 2013, I
> > think it is OK -- this patch is fixing something else.
> 
> I think the commit 9a9ab3cc00dc theoletically wrong because it uses
> __pa() on percpu address. But that is not guaranteed according to the
> comment on per_cpu_ptr_to_phys() as below.
> 
> ----
>  * percpu allocator has special setup for the first chunk, which currently
>  * supports either embedding in linear address space or vmalloc mapping,
>  * and, from the second one, the backing allocator (currently either vm or
>  * km) provides translation.
>  *
>  * The addr can be translated simply without checking if it falls into the
>  * first chunk. But the current code reflects better how percpu allocator
>  * actually works, and the verification can discover both bugs in percpu
>  * allocator itself and per_cpu_ptr_to_phys() callers. So we keep current
>  * code.
> ----
> 
> So we must use per_cpu_ptr_to_phys() instead of __pa() macro for percpu
> address. That's why I pointed this will fix the commit 9a9ab3cc00dc.

Thank you for the analysis. We are going to try to get the patch
upstream as soon as we can.

Re: [PATCH] arm/arm64: xen: Fix to convert percpu address to gfn correctly

Posted by Masami Hiramatsu 3 weeks ago
On Tue, 6 Oct 2020 10:56:52 -0700 (PDT)
Stefano Stabellini <sstabellini@kernel.org> wrote:

> On Tue, 6 Oct 2020, Masami Hiramatsu wrote:
> > On Mon, 5 Oct 2020 18:13:22 -0700 (PDT)
> > Stefano Stabellini <sstabellini@kernel.org> wrote:
> > 
> > > On Mon, 5 Oct 2020, Julien Grall wrote:
> > > > Hi Masami,
> > > > 
> > > > On 05/10/2020 14:39, Masami Hiramatsu wrote:
> > > > > Use per_cpu_ptr_to_phys() instead of virt_to_phys() for per-cpu
> > > > > address conversion.
> > > > > 
> > > > > In xen_starting_cpu(), per-cpu xen_vcpu_info address is converted
> > > > > to gfn by virt_to_gfn() macro. However, since the virt_to_gfn(v)
> > > > > assumes the given virtual address is in contiguous kernel memory
> > > > > area, it can not convert the per-cpu memory if it is allocated on
> > > > > vmalloc area (depends on CONFIG_SMP).
> > > > 
> > > > Are you sure about this? I have a .config with CONFIG_SMP=y where the per-cpu
> > > > region for CPU0 is allocated outside of vmalloc area.
> > > > 
> > > > However, I was able to trigger the bug as soon as CONFIG_NUMA_BALANCING was
> > > > enabled.
> > > 
> > > I cannot reproduce the issue with defconfig, but I can with Masami's
> > > kconfig.
> > > 
> > > If I disable just CONFIG_NUMA_BALANCING from Masami's kconfig, the
> > > problem still appears.
> > > 
> > > If I disable CONFIG_NUMA from Masami's kconfig, it works, which is
> > > strange because CONFIG_NUMA is enabled in defconfig, and defconfig
> > > works.
> > 
> > Hmm, strange, because when I disabled CONFIG_NUMA_BALANCING, the issue
> > disappeared.
> > 
> > --- config-5.9.0-rc4+   2020-10-06 11:36:20.620107129 +0900
> > +++ config-5.9.0-rc4+.buggy     2020-10-05 21:04:40.369936461 +0900
> > @@ -131,7 +131,8 @@
> >  CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y
> >  CONFIG_CC_HAS_INT128=y
> >  CONFIG_ARCH_SUPPORTS_INT128=y
> > -# CONFIG_NUMA_BALANCING is not set
> > +CONFIG_NUMA_BALANCING=y
> > +CONFIG_NUMA_BALANCING_DEFAULT_ENABLED=y
> >  CONFIG_CGROUPS=y
> >  CONFIG_PAGE_COUNTER=y
> >  CONFIG_MEMCG=y
> > 
> > So buggy config just enabled NUMA_BALANCING (and default enabled)
> 
> Yeah but both NUMA and NUMA_BALANCING are enabled in defconfig which
> works fine...
> 
> [...]
> 
> > > The fix is fine for me. I tested it and it works. We need to remove the
> > > "Fixes:" line from the commit message. Ideally, replacing it with a
> > > reference to what is the source of the problem.
> > 
> > OK, as I said, it seems commit 9a9ab3cc00dc ("xen/arm: SMP support") has
> > introduced the per-cpu code. So note it instead of Fixes tag.
> 
> ...and commit 9a9ab3cc00dc was already present in 5.8 which also works
> fine with your kconfig. Something else changed in 5.9 causing this
> breakage as a side effect. Commit 9a9ab3cc00dc is there since 2013, I
> think it is OK -- this patch is fixing something else.

Hmm, then it might be someone runs out the first chunk of percpu and
xen uses the 2nd chunk which is in vmalloc area. It is possible if the
other initcall functions uses alloc_percpu().

Maybe we can trace percpu chunk allocation function for both case.

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [PATCH] arm/arm64: xen: Fix to convert percpu address to gfn correctly

Posted by Masami Hiramatsu 3 weeks ago
On Tue, 6 Oct 2020 11:40:58 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> On Mon, 5 Oct 2020 18:13:22 -0700 (PDT)
> Stefano Stabellini <sstabellini@kernel.org> wrote:
> 
> > On Mon, 5 Oct 2020, Julien Grall wrote:
> > > Hi Masami,
> > > 
> > > On 05/10/2020 14:39, Masami Hiramatsu wrote:
> > > > Use per_cpu_ptr_to_phys() instead of virt_to_phys() for per-cpu
> > > > address conversion.
> > > > 
> > > > In xen_starting_cpu(), per-cpu xen_vcpu_info address is converted
> > > > to gfn by virt_to_gfn() macro. However, since the virt_to_gfn(v)
> > > > assumes the given virtual address is in contiguous kernel memory
> > > > area, it can not convert the per-cpu memory if it is allocated on
> > > > vmalloc area (depends on CONFIG_SMP).
> > > 
> > > Are you sure about this? I have a .config with CONFIG_SMP=y where the per-cpu
> > > region for CPU0 is allocated outside of vmalloc area.
> > > 
> > > However, I was able to trigger the bug as soon as CONFIG_NUMA_BALANCING was
> > > enabled.
> > 
> > I cannot reproduce the issue with defconfig, but I can with Masami's
> > kconfig.
> > 
> > If I disable just CONFIG_NUMA_BALANCING from Masami's kconfig, the
> > problem still appears.
> > 
> > If I disable CONFIG_NUMA from Masami's kconfig, it works, which is
> > strange because CONFIG_NUMA is enabled in defconfig, and defconfig
> > works.
> 
> Hmm, strange, because when I disabled CONFIG_NUMA_BALANCING, the issue
> disappeared.

Ah, OK. It depends on NUMA. On arm64, CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK
is enabled if CONFIG_NUMA=y.

Since per-cpu first chunk has been allocated by memblock if the
CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK is enabled(See
pcpu_embed_first_chunk()), when the kernel allocate the xen_vcpu_info
on the first chunk, it will be in the linear address space.
However, if we disable CONFIG_NUMA, it will be on vmalloc page.

And if the first chunk has been filled up before initializing xen,
the xen_vcpu_info will be allocated on the 2nd chunk which is has been
allocated by the backend allocator (kernel memory or vmalloc, depends
on CONFIG_SMP).

So anyway we have to check it carefully with a special function, which is
per_cpu_ptr_to_phys(). 

Thank you,


-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [PATCH] arm/arm64: xen: Fix to convert percpu address to gfn correctly

Posted by Masami Hiramatsu 3 weeks ago
On Mon, 5 Oct 2020 19:18:47 +0100
Julien Grall <julien@xen.org> wrote:

> Hi Masami,
> 
> On 05/10/2020 14:39, Masami Hiramatsu wrote:
> > Use per_cpu_ptr_to_phys() instead of virt_to_phys() for per-cpu
> > address conversion.
> > 
> > In xen_starting_cpu(), per-cpu xen_vcpu_info address is converted
> > to gfn by virt_to_gfn() macro. However, since the virt_to_gfn(v)
> > assumes the given virtual address is in contiguous kernel memory
> > area, it can not convert the per-cpu memory if it is allocated on
> > vmalloc area (depends on CONFIG_SMP).
> 
> Are you sure about this? I have a .config with CONFIG_SMP=y where the 
> per-cpu region for CPU0 is allocated outside of vmalloc area.
> 
> However, I was able to trigger the bug as soon as CONFIG_NUMA_BALANCING 
> was enabled.

OK, I've confirmed that this depends on CONFIG_NUMA_BALANCING instead
of CONFIG_SMP. I'll update the comment.

> 
> [...]
> 
> > Fixes: 250c9af3d831 ("arm/xen: Add support for 64KB page granularity")
> 
> FWIW, I think the bug was already present before 250c9af3d831.

Hm, it seems commit 9a9ab3cc00dc ("xen/arm: SMP support") has introduced
the per-cpu code.

Thank you,

> 
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > ---
> >   arch/arm/xen/enlighten.c |    2 +-
> >   include/xen/arm/page.h   |    3 +++
> >   2 files changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> > index e93145d72c26..a6ab3689b2f4 100644
> > --- a/arch/arm/xen/enlighten.c
> > +++ b/arch/arm/xen/enlighten.c
> > @@ -150,7 +150,7 @@ static int xen_starting_cpu(unsigned int cpu)
> >   	pr_info("Xen: initializing cpu%d\n", cpu);
> >   	vcpup = per_cpu_ptr(xen_vcpu_info, cpu);
> >   
> > -	info.mfn = virt_to_gfn(vcpup);
> > +	info.mfn = percpu_to_gfn(vcpup);
> >   	info.offset = xen_offset_in_page(vcpup);
> >   
> >   	err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, xen_vcpu_nr(cpu),
> > diff --git a/include/xen/arm/page.h b/include/xen/arm/page.h
> > index 39df751d0dc4..ac1b65470563 100644
> > --- a/include/xen/arm/page.h
> > +++ b/include/xen/arm/page.h
> > @@ -83,6 +83,9 @@ static inline unsigned long bfn_to_pfn(unsigned long bfn)
> >   	})
> >   #define gfn_to_virt(m)		(__va(gfn_to_pfn(m) << XEN_PAGE_SHIFT))
> >   
> > +#define percpu_to_gfn(v)	\
> > +	(pfn_to_gfn(per_cpu_ptr_to_phys(v) >> XEN_PAGE_SHIFT))
> > +
> >   /* Only used in PV code. But ARM guests are always HVM. */
> >   static inline xmaddr_t arbitrary_virt_to_machine(void *vaddr)
> >   {
> > 
> 
> Cheers,
> 
> -- 
> Julien Grall


-- 
Masami Hiramatsu <mhiramat@kernel.org>