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[PATCH v2 09/12] x86: make mem-paging configuarable and default it to off for being unsupported
jbeulich at suse
Apr 12, 2021, 7:12 AM
Post #1 of 7 (20 views)
Permalink
While doing so, make the option dependent upon HVM, which really is the
main purpose of the change.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v2: New.

--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -15,7 +15,6 @@ config X86
select HAS_FAST_MULTIPLY
select HAS_IOPORTS
select HAS_KEXEC
- select HAS_MEM_PAGING
select HAS_NS16550
select HAS_PASSTHROUGH
select HAS_PCI
@@ -251,6 +250,10 @@ config HYPERV_GUEST

endif

+config MEM_PAGING
+ bool "Xen memory paging support (UNSUPPORTED)" if UNSUPPORTED
+ depends on HVM
+
config MEM_SHARING
bool "Xen memory sharing support (UNSUPPORTED)" if UNSUPPORTED
depends on HVM
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1932,9 +1932,11 @@ int hvm_hap_nested_page_fault(paddr_t gp
goto out_put_gfn;
}

+#ifdef CONFIG_MEM_PAGING
/* Check if the page has been paged out */
if ( p2m_is_paged(p2mt) || (p2mt == p2m_ram_paging_out) )
paged = 1;
+#endif

#ifdef CONFIG_MEM_SHARING
/* Mem sharing: if still shared on write access then its enomem */
--- a/xen/arch/x86/mm/Makefile
+++ b/xen/arch/x86/mm/Makefile
@@ -5,7 +5,7 @@ obj-$(CONFIG_HVM) += altp2m.o
obj-$(CONFIG_HVM) += guest_walk_2.o guest_walk_3.o guest_walk_4.o
obj-$(CONFIG_SHADOW_PAGING) += guest_walk_4.o
obj-$(CONFIG_MEM_ACCESS) += mem_access.o
-obj-y += mem_paging.o
+obj-$(CONFIG_MEM_PAGING) += mem_paging.o
obj-$(CONFIG_MEM_SHARING) += mem_sharing.o
obj-y += p2m.o p2m-pt.o
obj-$(CONFIG_HVM) += p2m-ept.o p2m-pod.o
--- a/xen/arch/x86/x86_64/compat/mm.c
+++ b/xen/arch/x86/x86_64/compat/mm.c
@@ -155,8 +155,10 @@ int compat_arch_memory_op(unsigned long
case XENMEM_get_sharing_shared_pages:
return mem_sharing_get_nr_shared_mfns();

+#ifdef CONFIG_MEM_PAGING
case XENMEM_paging_op:
return mem_paging_memop(guest_handle_cast(arg, xen_mem_paging_op_t));
+#endif

#ifdef CONFIG_MEM_SHARING
case XENMEM_sharing_op:
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -994,8 +994,10 @@ long subarch_memory_op(unsigned long cmd
case XENMEM_get_sharing_shared_pages:
return mem_sharing_get_nr_shared_mfns();

+#ifdef CONFIG_MEM_PAGING
case XENMEM_paging_op:
return mem_paging_memop(guest_handle_cast(arg, xen_mem_paging_op_t));
+#endif

#ifdef CONFIG_MEM_SHARING
case XENMEM_sharing_op:
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -40,9 +40,6 @@ config HAS_IOPORTS
config HAS_KEXEC
bool

-config HAS_MEM_PAGING
- bool
-
config HAS_PDX
bool

--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1096,7 +1096,7 @@ static void complete_domain_destroy(stru
free_xenoprof_pages(d);
#endif

-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
xfree(d->vm_event_paging);
#endif
xfree(d->vm_event_monitor);
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -1856,7 +1856,7 @@ int check_get_page_from_gfn(struct domai

page = get_page_from_gfn(d, gfn_x(gfn), &p2mt, q);

-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
if ( p2m_is_paging(p2mt) )
{
if ( page )
--- a/xen/common/vm_event.c
+++ b/xen/common/vm_event.c
@@ -390,7 +390,7 @@ static int vm_event_resume(struct domain
/* Check flags which apply only when the vCPU is paused */
if ( atomic_read(&v->vm_event_pause_count) )
{
-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
if ( rsp.reason == VM_EVENT_REASON_MEM_PAGING )
p2m_mem_paging_resume(d, &rsp);
#endif
@@ -521,7 +521,7 @@ int __vm_event_claim_slot(struct domain
return vm_event_grab_slot(ved, current->domain != d);
}

-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
/* Registered with Xen-bound event channel for incoming notifications. */
static void mem_paging_notification(struct vcpu *v, unsigned int port)
{
@@ -546,7 +546,7 @@ static void mem_sharing_notification(str
/* Clean up on domain destruction */
void vm_event_cleanup(struct domain *d)
{
-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
if ( vm_event_check_ring(d->vm_event_paging) )
{
/* Destroying the wait queue head means waking up all
@@ -613,7 +613,7 @@ int vm_event_domctl(struct domain *d, st

switch ( vec->mode )
{
-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
case XEN_DOMCTL_VM_EVENT_OP_PAGING:
{
rc = -EINVAL;
--- a/xen/drivers/passthrough/x86/iommu.c
+++ b/xen/drivers/passthrough/x86/iommu.c
@@ -23,6 +23,7 @@

#include <asm/hvm/io.h>
#include <asm/io_apic.h>
+#include <asm/mem_paging.h>
#include <asm/setup.h>

const struct iommu_init_ops *__initdata iommu_init_ops;
@@ -336,7 +337,7 @@ bool arch_iommu_use_permitted(const stru
*/
return d == dom_io ||
(likely(!mem_sharing_enabled(d)) &&
- likely(!vm_event_check_ring(d->vm_event_paging)) &&
+ likely(!mem_paging_enabled(d)) &&
likely(!p2m_get_hostp2m(d)->global_logdirty));
}

--- a/xen/include/asm-x86/mem_paging.h
+++ b/xen/include/asm-x86/mem_paging.h
@@ -24,6 +24,12 @@

int mem_paging_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_paging_op_t) arg);

+#ifdef CONFIG_MEM_PAGING
+# define mem_paging_enabled(d) vm_event_check_ring((d)->vm_event_paging)
+#else
+# define mem_paging_enabled(d) false
+#endif
+
#endif /*__ASM_X86_MEM_PAGING_H__ */

/*
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -136,11 +136,16 @@ typedef unsigned int p2m_query_t;
#define P2M_PAGEABLE_TYPES (p2m_to_mask(p2m_ram_rw) \
| p2m_to_mask(p2m_ram_logdirty) )

+#ifdef CONFIG_MEM_PAGING
#define P2M_PAGING_TYPES (p2m_to_mask(p2m_ram_paging_out) \
| p2m_to_mask(p2m_ram_paged) \
| p2m_to_mask(p2m_ram_paging_in))

#define P2M_PAGED_TYPES (p2m_to_mask(p2m_ram_paged))
+#else
+#define P2M_PAGING_TYPES 0
+#define P2M_PAGED_TYPES 0
+#endif

/* Shared types */
/* XXX: Sharable types could include p2m_ram_ro too, but we would need to
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -530,7 +530,7 @@ struct domain
struct domain *parent; /* VM fork parent */
#endif
/* Memory paging support */
-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
struct vm_event_domain *vm_event_paging;
#endif
/* VM event monitor support */
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -592,7 +592,7 @@ static XSM_INLINE int xsm_mem_access(XSM
}
#endif

-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
static XSM_INLINE int xsm_mem_paging(XSM_DEFAULT_ARG struct domain *d)
{
XSM_ASSERT_ACTION(XSM_DM_PRIV);
--- a/xen/include/xsm/xsm.h
+++ b/xen/include/xsm/xsm.h
@@ -146,7 +146,7 @@ struct xsm_operations {
int (*mem_access) (struct domain *d);
#endif

-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
int (*mem_paging) (struct domain *d);
#endif

@@ -592,7 +592,7 @@ static inline int xsm_mem_access (xsm_de
}
#endif

-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
static inline int xsm_mem_paging (xsm_default_t def, struct domain *d)
{
return xsm_ops->mem_paging(d);
--- a/xen/xsm/dummy.c
+++ b/xen/xsm/dummy.c
@@ -124,7 +124,7 @@ void __init xsm_fixup_ops (struct xsm_op
set_to_dummy_if_null(ops, mem_access);
#endif

-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
set_to_dummy_if_null(ops, mem_paging);
#endif

--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -1256,7 +1256,7 @@ static int flask_mem_access(struct domai
}
#endif

-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
static int flask_mem_paging(struct domain *d)
{
return current_has_perm(d, SECCLASS_DOMAIN2, DOMAIN2__MEM_PAGING);
@@ -1829,7 +1829,7 @@ static struct xsm_operations flask_ops =
.mem_access = flask_mem_access,
#endif

-#ifdef CONFIG_HAS_MEM_PAGING
+#ifdef CONFIG_MEM_PAGING
.mem_paging = flask_mem_paging,
#endif
Re: [PATCH v2 09/12] x86: make mem-paging configuarable and default it to off for being unsupported [ In reply to ]
tamas at tklengyel
Apr 12, 2021, 7:18 AM
Post #2 of 7 (20 views)
Permalink
On Mon, Apr 12, 2021 at 10:12 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> While doing so, make the option dependent upon HVM, which really is the
> main purpose of the change.

IMHO it would be better to just remove this dead code altogether.

Tamas
Re: [PATCH v2 09/12] x86: make mem-paging configuarable and default it to off for being unsupported [ In reply to ]
aisaila at bitdefender
Apr 12, 2021, 7:27 AM
Post #3 of 7 (20 views)
Permalink
On 12.04.2021 17:12, Jan Beulich wrote:
> CAUTION: This email originated from outside of our organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
>
> While doing so, make the option dependent upon HVM, which really is the
> main purpose of the change.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Alexandru Isaila <aisaila@bitdefender.com>
Re: [PATCH v2 09/12] x86: make mem-paging configuarable and default it to off for being unsupported [ In reply to ]
aisaila at bitdefender
Apr 12, 2021, 7:47 AM
Post #4 of 7 (20 views)
Permalink
On 12.04.2021 17:18, Tamas K Lengyel wrote:
> CAUTION: This email originated from outside of our organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
>
> On Mon, Apr 12, 2021 at 10:12 AM Jan Beulich <jbeulich@suse.com> wrote:
>>
>> While doing so, make the option dependent upon HVM, which really is the
>> main purpose of the change.
>
> IMHO it would be better to just remove this dead code altogether.
>

I agree with Tamas here.

Alex
Re: [PATCH v2 09/12] x86: make mem-paging configuarable and default it to off for being unsupported [ In reply to ]
roger.pau at citrix
Apr 30, 2021, 2:55 AM
Post #5 of 7 (20 views)
Permalink
On Mon, Apr 12, 2021 at 04:12:41PM +0200, Jan Beulich wrote:
> While doing so, make the option dependent upon HVM, which really is the
> main purpose of the change.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> ---
> v2: New.
>
> --- a/xen/arch/x86/Kconfig
> +++ b/xen/arch/x86/Kconfig
> @@ -15,7 +15,6 @@ config X86
> select HAS_FAST_MULTIPLY
> select HAS_IOPORTS
> select HAS_KEXEC
> - select HAS_MEM_PAGING
> select HAS_NS16550
> select HAS_PASSTHROUGH
> select HAS_PCI
> @@ -251,6 +250,10 @@ config HYPERV_GUEST
>
> endif
>
> +config MEM_PAGING
> + bool "Xen memory paging support (UNSUPPORTED)" if UNSUPPORTED
> + depends on HVM
> +
> config MEM_SHARING
> bool "Xen memory sharing support (UNSUPPORTED)" if UNSUPPORTED
> depends on HVM
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -1932,9 +1932,11 @@ int hvm_hap_nested_page_fault(paddr_t gp
> goto out_put_gfn;
> }
>
> +#ifdef CONFIG_MEM_PAGING
> /* Check if the page has been paged out */
> if ( p2m_is_paged(p2mt) || (p2mt == p2m_ram_paging_out) )
> paged = 1;
> +#endif
>
> #ifdef CONFIG_MEM_SHARING
> /* Mem sharing: if still shared on write access then its enomem */
> --- a/xen/arch/x86/mm/Makefile
> +++ b/xen/arch/x86/mm/Makefile
> @@ -5,7 +5,7 @@ obj-$(CONFIG_HVM) += altp2m.o
> obj-$(CONFIG_HVM) += guest_walk_2.o guest_walk_3.o guest_walk_4.o
> obj-$(CONFIG_SHADOW_PAGING) += guest_walk_4.o
> obj-$(CONFIG_MEM_ACCESS) += mem_access.o
> -obj-y += mem_paging.o
> +obj-$(CONFIG_MEM_PAGING) += mem_paging.o
> obj-$(CONFIG_MEM_SHARING) += mem_sharing.o
> obj-y += p2m.o p2m-pt.o
> obj-$(CONFIG_HVM) += p2m-ept.o p2m-pod.o
> --- a/xen/arch/x86/x86_64/compat/mm.c
> +++ b/xen/arch/x86/x86_64/compat/mm.c
> @@ -155,8 +155,10 @@ int compat_arch_memory_op(unsigned long
> case XENMEM_get_sharing_shared_pages:
> return mem_sharing_get_nr_shared_mfns();
>
> +#ifdef CONFIG_MEM_PAGING
> case XENMEM_paging_op:
> return mem_paging_memop(guest_handle_cast(arg, xen_mem_paging_op_t));
> +#endif
>
> #ifdef CONFIG_MEM_SHARING
> case XENMEM_sharing_op:
> --- a/xen/arch/x86/x86_64/mm.c
> +++ b/xen/arch/x86/x86_64/mm.c
> @@ -994,8 +994,10 @@ long subarch_memory_op(unsigned long cmd
> case XENMEM_get_sharing_shared_pages:
> return mem_sharing_get_nr_shared_mfns();
>
> +#ifdef CONFIG_MEM_PAGING
> case XENMEM_paging_op:
> return mem_paging_memop(guest_handle_cast(arg, xen_mem_paging_op_t));
> +#endif

I would create a dummy handler when !CONFIG_MEM_PAGING in
asm-x86/mem_paging.h.

> --- a/xen/include/asm-x86/mem_paging.h
> +++ b/xen/include/asm-x86/mem_paging.h
> @@ -24,6 +24,12 @@
>
> int mem_paging_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_paging_op_t) arg);
>
> +#ifdef CONFIG_MEM_PAGING
> +# define mem_paging_enabled(d) vm_event_check_ring((d)->vm_event_paging)
> +#else
> +# define mem_paging_enabled(d) false
> +#endif
> +
> #endif /*__ASM_X86_MEM_PAGING_H__ */
>
> /*
> --- a/xen/include/asm-x86/p2m.h
> +++ b/xen/include/asm-x86/p2m.h
> @@ -136,11 +136,16 @@ typedef unsigned int p2m_query_t;
> #define P2M_PAGEABLE_TYPES (p2m_to_mask(p2m_ram_rw) \
> | p2m_to_mask(p2m_ram_logdirty) )
>
> +#ifdef CONFIG_MEM_PAGING
> #define P2M_PAGING_TYPES (p2m_to_mask(p2m_ram_paging_out) \
> | p2m_to_mask(p2m_ram_paged) \
> | p2m_to_mask(p2m_ram_paging_in))
>
> #define P2M_PAGED_TYPES (p2m_to_mask(p2m_ram_paged))
> +#else
> +#define P2M_PAGING_TYPES 0
> +#define P2M_PAGED_TYPES 0
> +#endif

Since you don't guard the p2m related paged types in p2m_type_t is it
worth having diverging P2M_{PAGING/PAGED}_TYPES?

I guess it might be required in order to force the compiler to DCE
without having to add yet more CONFIG_MEM_PAGING guards?

I don't really have a strong opinion on whether the code should be
removed, IMO it's best to start by making it off by default at build
time and remove it in a later release?

Thanks, Roger.
Re: [PATCH v2 09/12] x86: make mem-paging configuarable and default it to off for being unsupported [ In reply to ]
jbeulich at suse
Apr 30, 2021, 7:16 AM
Post #6 of 7 (20 views)
Permalink
On 30.04.2021 11:55, Roger Pau Monné wrote:
> On Mon, Apr 12, 2021 at 04:12:41PM +0200, Jan Beulich wrote:
>> --- a/xen/arch/x86/x86_64/compat/mm.c
>> +++ b/xen/arch/x86/x86_64/compat/mm.c
>> @@ -155,8 +155,10 @@ int compat_arch_memory_op(unsigned long
>> case XENMEM_get_sharing_shared_pages:
>> return mem_sharing_get_nr_shared_mfns();
>>
>> +#ifdef CONFIG_MEM_PAGING
>> case XENMEM_paging_op:
>> return mem_paging_memop(guest_handle_cast(arg, xen_mem_paging_op_t));
>> +#endif
>>
>> #ifdef CONFIG_MEM_SHARING
>> case XENMEM_sharing_op:
>> --- a/xen/arch/x86/x86_64/mm.c
>> +++ b/xen/arch/x86/x86_64/mm.c
>> @@ -994,8 +994,10 @@ long subarch_memory_op(unsigned long cmd
>> case XENMEM_get_sharing_shared_pages:
>> return mem_sharing_get_nr_shared_mfns();
>>
>> +#ifdef CONFIG_MEM_PAGING
>> case XENMEM_paging_op:
>> return mem_paging_memop(guest_handle_cast(arg, xen_mem_paging_op_t));
>> +#endif
>
> I would create a dummy handler when !CONFIG_MEM_PAGING in
> asm-x86/mem_paging.h.

I was simply following the neighboring mem-sharing approach,
which you've stripped here, but which is still visible in the
xen/arch/x86/x86_64/compat/mm.c change above. I think the two
are helpful to be similar in such aspects.

>> --- a/xen/include/asm-x86/p2m.h
>> +++ b/xen/include/asm-x86/p2m.h
>> @@ -136,11 +136,16 @@ typedef unsigned int p2m_query_t;
>> #define P2M_PAGEABLE_TYPES (p2m_to_mask(p2m_ram_rw) \
>> | p2m_to_mask(p2m_ram_logdirty) )
>>
>> +#ifdef CONFIG_MEM_PAGING
>> #define P2M_PAGING_TYPES (p2m_to_mask(p2m_ram_paging_out) \
>> | p2m_to_mask(p2m_ram_paged) \
>> | p2m_to_mask(p2m_ram_paging_in))
>>
>> #define P2M_PAGED_TYPES (p2m_to_mask(p2m_ram_paged))
>> +#else
>> +#define P2M_PAGING_TYPES 0
>> +#define P2M_PAGED_TYPES 0
>> +#endif
>
> Since you don't guard the p2m related paged types in p2m_type_t is it
> worth having diverging P2M_{PAGING/PAGED}_TYPES?
>
> I guess it might be required in order to force the compiler to DCE
> without having to add yet more CONFIG_MEM_PAGING guards?

Indeed, this is the reason.

> I don't really have a strong opinion on whether the code should be
> removed, IMO it's best to start by making it off by default at build
> time and remove it in a later release?

Matches my way of thinking. I also wouldn't want to be the one to
delete code completely out of the blue.

Jan
Re: [PATCH v2 09/12] x86: make mem-paging configuarable and default it to off for being unsupported [ In reply to ]
roger.pau at citrix
Apr 30, 2021, 7:37 AM
Post #7 of 7 (20 views)
Permalink
On Fri, Apr 30, 2021 at 04:16:24PM +0200, Jan Beulich wrote:
> On 30.04.2021 11:55, Roger Pau Monné wrote:
> > On Mon, Apr 12, 2021 at 04:12:41PM +0200, Jan Beulich wrote:
> >> --- a/xen/arch/x86/x86_64/compat/mm.c
> >> +++ b/xen/arch/x86/x86_64/compat/mm.c
> >> @@ -155,8 +155,10 @@ int compat_arch_memory_op(unsigned long
> >> case XENMEM_get_sharing_shared_pages:
> >> return mem_sharing_get_nr_shared_mfns();
> >>
> >> +#ifdef CONFIG_MEM_PAGING
> >> case XENMEM_paging_op:
> >> return mem_paging_memop(guest_handle_cast(arg, xen_mem_paging_op_t));
> >> +#endif
> >>
> >> #ifdef CONFIG_MEM_SHARING
> >> case XENMEM_sharing_op:
> >> --- a/xen/arch/x86/x86_64/mm.c
> >> +++ b/xen/arch/x86/x86_64/mm.c
> >> @@ -994,8 +994,10 @@ long subarch_memory_op(unsigned long cmd
> >> case XENMEM_get_sharing_shared_pages:
> >> return mem_sharing_get_nr_shared_mfns();
> >>
> >> +#ifdef CONFIG_MEM_PAGING
> >> case XENMEM_paging_op:
> >> return mem_paging_memop(guest_handle_cast(arg, xen_mem_paging_op_t));
> >> +#endif
> >
> > I would create a dummy handler when !CONFIG_MEM_PAGING in
> > asm-x86/mem_paging.h.
>
> I was simply following the neighboring mem-sharing approach,
> which you've stripped here, but which is still visible in the
> xen/arch/x86/x86_64/compat/mm.c change above. I think the two
> are helpful to be similar in such aspects.
>
> >> --- a/xen/include/asm-x86/p2m.h
> >> +++ b/xen/include/asm-x86/p2m.h
> >> @@ -136,11 +136,16 @@ typedef unsigned int p2m_query_t;
> >> #define P2M_PAGEABLE_TYPES (p2m_to_mask(p2m_ram_rw) \
> >> | p2m_to_mask(p2m_ram_logdirty) )
> >>
> >> +#ifdef CONFIG_MEM_PAGING
> >> #define P2M_PAGING_TYPES (p2m_to_mask(p2m_ram_paging_out) \
> >> | p2m_to_mask(p2m_ram_paged) \
> >> | p2m_to_mask(p2m_ram_paging_in))
> >>
> >> #define P2M_PAGED_TYPES (p2m_to_mask(p2m_ram_paged))
> >> +#else
> >> +#define P2M_PAGING_TYPES 0
> >> +#define P2M_PAGED_TYPES 0
> >> +#endif
> >
> > Since you don't guard the p2m related paged types in p2m_type_t is it
> > worth having diverging P2M_{PAGING/PAGED}_TYPES?
> >
> > I guess it might be required in order to force the compiler to DCE
> > without having to add yet more CONFIG_MEM_PAGING guards?
>
> Indeed, this is the reason.
>
> > I don't really have a strong opinion on whether the code should be
> > removed, IMO it's best to start by making it off by default at build
> > time and remove it in a later release?
>
> Matches my way of thinking. I also wouldn't want to be the one to
> delete code completely out of the blue.

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks.

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