[PATCH v4 26/30] xen/riscv: add minimal stuff to mm.h to build full Xen

Oleksii Kurochko posted 30 patches 7 months ago
There is a newer version of this series
[PATCH v4 26/30] xen/riscv: add minimal stuff to mm.h to build full Xen
Posted by Oleksii Kurochko 7 months ago
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
---
Changes in V4:
 - update an argument name of PFN_ORDERN macros.
 - drop pad at the end of 'struct page_info'.
 - Change message -> subject in "Changes in V3"
 - delete duplicated macros from riscv/mm.h
 - fix identation in struct page_info
 - align comment for PGC_ macros
 - update definitions of domain_set_alloc_bitsize() and domain_clamp_alloc_bitsize()
 - drop unnessary comments.
 - s/BUG/BUG_ON("...")
 - define __virt_to_maddr, __maddr_to_virt as stubs
 - add inclusion of xen/mm-frame.h for mfn_x and others
 - include "xen/mm.h" instead of "asm/mm.h" to fix compilation issues:
	 In file included from arch/riscv/setup.c:7:
	./arch/riscv/include/asm/mm.h:60:28: error: field 'list' has incomplete type
	   60 |     struct page_list_entry list;
	      |                            ^~~~
	./arch/riscv/include/asm/mm.h:81:43: error: 'MAX_ORDER' undeclared here (not in a function)
	   81 |                 unsigned long first_dirty:MAX_ORDER + 1;
	      |                                           ^~~~~~~~~
	./arch/riscv/include/asm/mm.h:81:31: error: bit-field 'first_dirty' width not an integer constant
	   81 |                 unsigned long first_dirty:MAX_ORDER + 1;
 - Define __virt_to_mfn() and __mfn_to_virt() using maddr_to_mfn() and mfn_to_maddr().
---
Changes in V3:
 - update the commit title
 - introduce DIRECTMAP_VIRT_START.
 - drop changes related pfn_to_paddr() and paddr_to_pfn as they were remvoe in
   [PATCH v2 32/39] xen/riscv: add minimal stuff to asm/page.h to build full Xen
 - code style fixes.
 - drop get_page_nr  and put_page_nr as they don't need for time being
 - drop CONFIG_STATIC_MEMORY related things
 - code style fixes
---
Changes in V2:
 - define stub for arch_get_dma_bitsize(void)
---
 xen/arch/riscv/include/asm/mm.h | 246 ++++++++++++++++++++++++++++++++
 xen/arch/riscv/mm.c             |   2 +-
 xen/arch/riscv/setup.c          |   2 +-
 3 files changed, 248 insertions(+), 2 deletions(-)

diff --git a/xen/arch/riscv/include/asm/mm.h b/xen/arch/riscv/include/asm/mm.h
index 07c7a0abba..0254babcc1 100644
--- a/xen/arch/riscv/include/asm/mm.h
+++ b/xen/arch/riscv/include/asm/mm.h
@@ -3,11 +3,252 @@
 #ifndef _ASM_RISCV_MM_H
 #define _ASM_RISCV_MM_H
 
+#include <public/xen.h>
+#include <xen/bug.h>
+#include <xen/mm-frame.h>
+#include <xen/pdx.h>
+#include <xen/types.h>
+
 #include <asm/page-bits.h>
 
 #define pfn_to_paddr(pfn) ((paddr_t)(pfn) << PAGE_SHIFT)
 #define paddr_to_pfn(pa)  ((unsigned long)((pa) >> PAGE_SHIFT))
 
+#define paddr_to_pdx(pa)    mfn_to_pdx(maddr_to_mfn(pa))
+#define gfn_to_gaddr(gfn)   pfn_to_paddr(gfn_x(gfn))
+#define gaddr_to_gfn(ga)    _gfn(paddr_to_pfn(ga))
+#define mfn_to_maddr(mfn)   pfn_to_paddr(mfn_x(mfn))
+#define maddr_to_mfn(ma)    _mfn(paddr_to_pfn(ma))
+#define vmap_to_mfn(va)     maddr_to_mfn(virt_to_maddr((vaddr_t)va))
+#define vmap_to_page(va)    mfn_to_page(vmap_to_mfn(va))
+
+static inline unsigned long __virt_to_maddr(unsigned long va)
+{
+    BUG_ON("unimplemented");
+    return 0;
+}
+
+static inline void *__maddr_to_virt(unsigned long ma)
+{
+    BUG_ON("unimplemented");
+    return NULL;
+}
+
+#define virt_to_maddr(va) __virt_to_maddr((unsigned long)(va))
+#define maddr_to_virt(pa) __maddr_to_virt((unsigned long)(pa))
+
+/* Convert between Xen-heap virtual addresses and machine frame numbers. */
+#define __virt_to_mfn(va)  mfn_x(maddr_to_mfn(virt_to_maddr(va)))
+#define __mfn_to_virt(mfn) maddr_to_virt(mfn_to_maddr(_mfn(mfn)))
+
+/* Convert between Xen-heap virtual addresses and page-info structures. */
+static inline struct page_info *virt_to_page(const void *v)
+{
+    BUG_ON("unimplemented");
+    return NULL;
+}
+
+/*
+ * We define non-underscored wrappers for above conversion functions.
+ * These are overriden in various source files while underscored version
+ * remain intact.
+ */
+#define virt_to_mfn(va)     __virt_to_mfn(va)
+#define mfn_to_virt(mfn)    __mfn_to_virt(mfn)
+
+struct page_info
+{
+    /* Each frame can be threaded onto a doubly-linked list. */
+    struct page_list_entry list;
+
+    /* Reference count and various PGC_xxx flags and fields. */
+    unsigned long count_info;
+
+    /* Context-dependent fields follow... */
+    union {
+        /* Page is in use: ((count_info & PGC_count_mask) != 0). */
+        struct {
+            /* Type reference count and various PGT_xxx flags and fields. */
+            unsigned long type_info;
+        } inuse;
+        /* Page is on a free list: ((count_info & PGC_count_mask) == 0). */
+        union {
+            struct {
+                /*
+                 * Index of the first *possibly* unscrubbed page in the buddy.
+                 * One more bit than maximum possible order to accommodate
+                 * INVALID_DIRTY_IDX.
+                 */
+#define INVALID_DIRTY_IDX ((1UL << (MAX_ORDER + 1)) - 1)
+                unsigned long first_dirty:MAX_ORDER + 1;
+
+                /* Do TLBs need flushing for safety before next page use? */
+                bool need_tlbflush:1;
+
+#define BUDDY_NOT_SCRUBBING    0
+#define BUDDY_SCRUBBING        1
+#define BUDDY_SCRUB_ABORT      2
+                unsigned long scrub_state:2;
+            };
+
+                unsigned long val;
+        } free;
+    } u;
+
+    union {
+        /* Page is in use, but not as a shadow. */
+        struct {
+            /* Owner of this page (zero if page is anonymous). */
+            struct domain *domain;
+        } inuse;
+
+        /* Page is on a free list. */
+        struct {
+            /* Order-size of the free chunk this page is the head of. */
+            unsigned int order;
+        } free;
+    } v;
+
+    union {
+        /*
+         * Timestamp from 'TLB clock', used to avoid extra safety flushes.
+         * Only valid for: a) free pages, and b) pages with zero type count
+         */
+        uint32_t tlbflush_timestamp;
+    };
+};
+
+#define frame_table ((struct page_info *)FRAMETABLE_VIRT_START)
+
+/* PDX of the first page in the frame table. */
+extern unsigned long frametable_base_pdx;
+
+/* Convert between machine frame numbers and page-info structures. */
+#define mfn_to_page(mfn)                                            \
+    (frame_table + (mfn_to_pdx(mfn) - frametable_base_pdx))
+#define page_to_mfn(pg)                                             \
+    pdx_to_mfn((unsigned long)((pg) - frame_table) + frametable_base_pdx)
+
+static inline void *page_to_virt(const struct page_info *pg)
+{
+    return mfn_to_virt(mfn_x(page_to_mfn(pg)));
+}
+
+/*
+ * Common code requires get_page_type and put_page_type.
+ * We don't care about typecounts so we just do the minimum to make it
+ * happy.
+ */
+static inline int get_page_type(struct page_info *page, unsigned long type)
+{
+    return 1;
+}
+
+static inline void put_page_type(struct page_info *page)
+{
+}
+
+static inline void put_page_and_type(struct page_info *page)
+{
+    put_page_type(page);
+    put_page(page);
+}
+
+/*
+ * RISC-V does not have an M2P, but common code expects a handful of
+ * M2P-related defines and functions. Provide dummy versions of these.
+ */
+#define INVALID_M2P_ENTRY        (~0UL)
+#define SHARED_M2P_ENTRY         (~0UL - 1UL)
+#define SHARED_M2P(_e)           ((_e) == SHARED_M2P_ENTRY)
+
+#define set_gpfn_from_mfn(mfn, pfn) do { (void)(mfn), (void)(pfn); } while (0)
+#define mfn_to_gfn(d, mfn) ((void)(d), _gfn(mfn_x(mfn)))
+
+#define PDX_GROUP_SHIFT (16 + 5)
+
+static inline unsigned long domain_get_maximum_gpfn(struct domain *d)
+{
+    BUG_ON("unimplemented");
+    return 0;
+}
+
+static inline long arch_memory_op(int op, XEN_GUEST_HANDLE_PARAM(void) arg)
+{
+    BUG_ON("unimplemented");
+    return 0;
+}
+
+/*
+ * On RISCV, all the RAM is currently direct mapped in Xen.
+ * Hence return always true.
+ */
+static inline bool arch_mfns_in_directmap(unsigned long mfn, unsigned long nr)
+{
+    return true;
+}
+
+#define PG_shift(idx)   (BITS_PER_LONG - (idx))
+#define PG_mask(x, idx) (x ## UL << PG_shift(idx))
+
+#define PGT_none          PG_mask(0, 1)  /* no special uses of this page   */
+#define PGT_writable_page PG_mask(1, 1)  /* has writable mappings?         */
+#define PGT_type_mask     PG_mask(1, 1)  /* Bits 31 or 63.                 */
+
+ /* Count of uses of this frame as its current type. */
+#define PGT_count_width   PG_shift(2)
+#define PGT_count_mask    ((1UL << PGT_count_width) - 1)
+
+/*
+ * Page needs to be scrubbed. Since this bit can only be set on a page that is
+ * free (i.e. in PGC_state_free) we can reuse PGC_allocated bit.
+ */
+#define _PGC_need_scrub   _PGC_allocated
+#define PGC_need_scrub    PGC_allocated
+
+/* Cleared when the owning guest 'frees' this page. */
+#define _PGC_allocated    PG_shift(1)
+#define PGC_allocated     PG_mask(1, 1)
+/* Page is Xen heap? */
+#define _PGC_xen_heap     PG_shift(2)
+#define PGC_xen_heap      PG_mask(1, 2)
+/* Page is broken? */
+#define _PGC_broken       PG_shift(7)
+#define PGC_broken        PG_mask(1, 7)
+/* Mutually-exclusive page states: { inuse, offlining, offlined, free }. */
+#define PGC_state         PG_mask(3, 9)
+#define PGC_state_inuse   PG_mask(0, 9)
+#define PGC_state_offlining PG_mask(1, 9)
+#define PGC_state_offlined PG_mask(2, 9)
+#define PGC_state_free    PG_mask(3, 9)
+#define page_state_is(pg, st) (((pg)->count_info&PGC_state) == PGC_state_##st)
+
+/* Count of references to this frame. */
+#define PGC_count_width   PG_shift(9)
+#define PGC_count_mask    ((1UL << PGC_count_width) - 1)
+
+#define _PGC_extra        PG_shift(10)
+#define PGC_extra         PG_mask(1, 10)
+
+#define is_xen_heap_page(page) ((page)->count_info & PGC_xen_heap)
+#define is_xen_heap_mfn(mfn) \
+    (mfn_valid(mfn) && is_xen_heap_page(mfn_to_page(mfn)))
+
+#define is_xen_fixed_mfn(mfn)                                   \
+    ((mfn_to_maddr(mfn) >= virt_to_maddr((vaddr_t)_start)) &&   \
+     (mfn_to_maddr(mfn) <= virt_to_maddr((vaddr_t)_end - 1)))
+
+#define page_get_owner(_p)    (_p)->v.inuse.domain
+#define page_set_owner(_p,_d) ((_p)->v.inuse.domain = (_d))
+
+/* TODO: implement */
+#define mfn_valid(mfn) ({ (void)(mfn); 0; })
+
+#define domain_set_alloc_bitsize(d) ((void)(d))
+#define domain_clamp_alloc_bitsize(d, b) ((void)(d), (b))
+
+#define PFN_ORDER(pfn) ((pfn)->v.free.order)
+
 extern unsigned char cpu0_boot_stack[];
 
 void setup_initial_pagetables(void);
@@ -20,4 +261,9 @@ unsigned long calc_phys_offset(void);
 
 void turn_on_mmu(unsigned long ra);
 
+static inline unsigned int arch_get_dma_bitsize(void)
+{
+    return 32; /* TODO */
+}
+
 #endif /* _ASM_RISCV_MM_H */
diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c
index 053f043a3d..fe3a43be20 100644
--- a/xen/arch/riscv/mm.c
+++ b/xen/arch/riscv/mm.c
@@ -5,12 +5,12 @@
 #include <xen/init.h>
 #include <xen/kernel.h>
 #include <xen/macros.h>
+#include <xen/mm.h>
 #include <xen/pfn.h>
 
 #include <asm/early_printk.h>
 #include <asm/csr.h>
 #include <asm/current.h>
-#include <asm/mm.h>
 #include <asm/page.h>
 #include <asm/processor.h>
 
diff --git a/xen/arch/riscv/setup.c b/xen/arch/riscv/setup.c
index 6593f601c1..98a94c4c48 100644
--- a/xen/arch/riscv/setup.c
+++ b/xen/arch/riscv/setup.c
@@ -2,9 +2,9 @@
 
 #include <xen/compile.h>
 #include <xen/init.h>
+#include <xen/mm.h>
 
 #include <asm/early_printk.h>
-#include <asm/mm.h>
 
 /* Xen stack for bringing up the first CPU. */
 unsigned char __initdata cpu0_boot_stack[STACK_SIZE]
-- 
2.43.0
Re: [PATCH v4 26/30] xen/riscv: add minimal stuff to mm.h to build full Xen
Posted by Jan Beulich 6 months, 3 weeks ago
On 05.02.2024 16:32, Oleksii Kurochko wrote:
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
> ---
> Changes in V4:
>  - update an argument name of PFN_ORDERN macros.
>  - drop pad at the end of 'struct page_info'.
>  - Change message -> subject in "Changes in V3"
>  - delete duplicated macros from riscv/mm.h
>  - fix identation in struct page_info

I'm sorry, but how does this fit ...

> +struct page_info
> +{
> +    /* Each frame can be threaded onto a doubly-linked list. */
> +    struct page_list_entry list;
> +
> +    /* Reference count and various PGC_xxx flags and fields. */
> +    unsigned long count_info;
> +
> +    /* Context-dependent fields follow... */
> +    union {
> +        /* Page is in use: ((count_info & PGC_count_mask) != 0). */
> +        struct {
> +            /* Type reference count and various PGT_xxx flags and fields. */
> +            unsigned long type_info;
> +        } inuse;
> +        /* Page is on a free list: ((count_info & PGC_count_mask) == 0). */
> +        union {
> +            struct {
> +                /*
> +                 * Index of the first *possibly* unscrubbed page in the buddy.
> +                 * One more bit than maximum possible order to accommodate
> +                 * INVALID_DIRTY_IDX.
> +                 */
> +#define INVALID_DIRTY_IDX ((1UL << (MAX_ORDER + 1)) - 1)
> +                unsigned long first_dirty:MAX_ORDER + 1;
> +
> +                /* Do TLBs need flushing for safety before next page use? */
> +                bool need_tlbflush:1;
> +
> +#define BUDDY_NOT_SCRUBBING    0
> +#define BUDDY_SCRUBBING        1
> +#define BUDDY_SCRUB_ABORT      2
> +                unsigned long scrub_state:2;
> +            };
> +
> +                unsigned long val;

... this?

> +        } free;
> +    } u;
> +
> +    union {
> +        /* Page is in use, but not as a shadow. */

I'm also pretty sure I asked before what shadow this comment alludes to.

> +        struct {
> +            /* Owner of this page (zero if page is anonymous). */
> +            struct domain *domain;

Seeing this is a pointer, I find "zero" in the comment a little
misleading. Better say NULL?

> +        } inuse;
> +
> +        /* Page is on a free list. */
> +        struct {
> +            /* Order-size of the free chunk this page is the head of. */
> +            unsigned int order;
> +        } free;
> +    } v;
> +
> +    union {
> +        /*
> +         * Timestamp from 'TLB clock', used to avoid extra safety flushes.
> +         * Only valid for: a) free pages, and b) pages with zero type count
> +         */
> +        uint32_t tlbflush_timestamp;
> +    };
> +};
> +
> +#define frame_table ((struct page_info *)FRAMETABLE_VIRT_START)
> +
> +/* PDX of the first page in the frame table. */
> +extern unsigned long frametable_base_pdx;
> +
> +/* Convert between machine frame numbers and page-info structures. */
> +#define mfn_to_page(mfn)                                            \
> +    (frame_table + (mfn_to_pdx(mfn) - frametable_base_pdx))
> +#define page_to_mfn(pg)                                             \
> +    pdx_to_mfn((unsigned long)((pg) - frame_table) + frametable_base_pdx)
> +
> +static inline void *page_to_virt(const struct page_info *pg)
> +{
> +    return mfn_to_virt(mfn_x(page_to_mfn(pg)));
> +}

Would be nice if this and the inverse function would live closer to
one another.

> +/*
> + * Common code requires get_page_type and put_page_type.
> + * We don't care about typecounts so we just do the minimum to make it
> + * happy.
> + */
> +static inline int get_page_type(struct page_info *page, unsigned long type)
> +{
> +    return 1;
> +}
> +
> +static inline void put_page_type(struct page_info *page)
> +{
> +}
> +
> +static inline void put_page_and_type(struct page_info *page)
> +{
> +    put_page_type(page);
> +    put_page(page);
> +}
> +
> +/*
> + * RISC-V does not have an M2P, but common code expects a handful of
> + * M2P-related defines and functions. Provide dummy versions of these.
> + */
> +#define INVALID_M2P_ENTRY        (~0UL)
> +#define SHARED_M2P_ENTRY         (~0UL - 1UL)
> +#define SHARED_M2P(_e)           ((_e) == SHARED_M2P_ENTRY)
> +
> +#define set_gpfn_from_mfn(mfn, pfn) do { (void)(mfn), (void)(pfn); } while (0)
> +#define mfn_to_gfn(d, mfn) ((void)(d), _gfn(mfn_x(mfn)))
> +
> +#define PDX_GROUP_SHIFT (16 + 5)

Where are these magic numbers coming from? None of the other three
architectures use literal numbers here, thus making clear what
values are actually meant. If you can't use suitable constants,
please add a comment.

> +static inline unsigned long domain_get_maximum_gpfn(struct domain *d)
> +{
> +    BUG_ON("unimplemented");
> +    return 0;
> +}
> +
> +static inline long arch_memory_op(int op, XEN_GUEST_HANDLE_PARAM(void) arg)
> +{
> +    BUG_ON("unimplemented");
> +    return 0;
> +}
> +
> +/*
> + * On RISCV, all the RAM is currently direct mapped in Xen.
> + * Hence return always true.
> + */
> +static inline bool arch_mfns_in_directmap(unsigned long mfn, unsigned long nr)
> +{
> +    return true;
> +}
> +
> +#define PG_shift(idx)   (BITS_PER_LONG - (idx))
> +#define PG_mask(x, idx) (x ## UL << PG_shift(idx))
> +
> +#define PGT_none          PG_mask(0, 1)  /* no special uses of this page   */
> +#define PGT_writable_page PG_mask(1, 1)  /* has writable mappings?         */
> +#define PGT_type_mask     PG_mask(1, 1)  /* Bits 31 or 63.                 */
> +
> + /* Count of uses of this frame as its current type. */

Imo the PGC_ related revision log item should have covered this one, too.

> +#define PGT_count_width   PG_shift(2)
> +#define PGT_count_mask    ((1UL << PGT_count_width) - 1)
> +
> +/*
> + * Page needs to be scrubbed. Since this bit can only be set on a page that is
> + * free (i.e. in PGC_state_free) we can reuse PGC_allocated bit.
> + */
> +#define _PGC_need_scrub   _PGC_allocated
> +#define PGC_need_scrub    PGC_allocated
> +
> +/* Cleared when the owning guest 'frees' this page. */
> +#define _PGC_allocated    PG_shift(1)
> +#define PGC_allocated     PG_mask(1, 1)
> +/* Page is Xen heap? */
> +#define _PGC_xen_heap     PG_shift(2)
> +#define PGC_xen_heap      PG_mask(1, 2)
> +/* Page is broken? */
> +#define _PGC_broken       PG_shift(7)
> +#define PGC_broken        PG_mask(1, 7)
> +/* Mutually-exclusive page states: { inuse, offlining, offlined, free }. */
> +#define PGC_state         PG_mask(3, 9)
> +#define PGC_state_inuse   PG_mask(0, 9)
> +#define PGC_state_offlining PG_mask(1, 9)
> +#define PGC_state_offlined PG_mask(2, 9)
> +#define PGC_state_free    PG_mask(3, 9)
> +#define page_state_is(pg, st) (((pg)->count_info&PGC_state) == PGC_state_##st)
> +
> +/* Count of references to this frame. */
> +#define PGC_count_width   PG_shift(9)
> +#define PGC_count_mask    ((1UL << PGC_count_width) - 1)
> +
> +#define _PGC_extra        PG_shift(10)
> +#define PGC_extra         PG_mask(1, 10)
> +
> +#define is_xen_heap_page(page) ((page)->count_info & PGC_xen_heap)
> +#define is_xen_heap_mfn(mfn) \
> +    (mfn_valid(mfn) && is_xen_heap_page(mfn_to_page(mfn)))
> +
> +#define is_xen_fixed_mfn(mfn)                                   \
> +    ((mfn_to_maddr(mfn) >= virt_to_maddr((vaddr_t)_start)) &&   \
> +     (mfn_to_maddr(mfn) <= virt_to_maddr((vaddr_t)_end - 1)))
> +
> +#define page_get_owner(_p)    (_p)->v.inuse.domain
> +#define page_set_owner(_p,_d) ((_p)->v.inuse.domain = (_d))

Unnecessary (leading) underscores again.

Jan
Re: [PATCH v4 26/30] xen/riscv: add minimal stuff to mm.h to build full Xen
Posted by Oleksii 6 months, 3 weeks ago
> 
> > +        } free;
> > +    } u;
> > +
> > +    union {
> > +        /* Page is in use, but not as a shadow. */
> 
> I'm also pretty sure I asked before what shadow this comment alludes
> to.
I missed your request about 'shadow' before.

The comment arrived from Arm.

I tried to find out the answer by investigation how 'inuse' is used,
and, unfortunately, I couldn't find an answer what 'shadow' alludes to.

> 
> > +/*
> > + * Common code requires get_page_type and put_page_type.
> > + * We don't care about typecounts so we just do the minimum to
> > make it
> > + * happy.
> > + */
> > +static inline int get_page_type(struct page_info *page, unsigned
> > long type)
> > +{
> > +    return 1;
> > +}
> > +
> > +static inline void put_page_type(struct page_info *page)
> > +{
> > +}
> > +
> > +static inline void put_page_and_type(struct page_info *page)
> > +{
> > +    put_page_type(page);
> > +    put_page(page);
> > +}
> > +
> > +/*
> > + * RISC-V does not have an M2P, but common code expects a handful
> > of
> > + * M2P-related defines and functions. Provide dummy versions of
> > these.
> > + */
> > +#define INVALID_M2P_ENTRY        (~0UL)
> > +#define SHARED_M2P_ENTRY         (~0UL - 1UL)
> > +#define SHARED_M2P(_e)           ((_e) == SHARED_M2P_ENTRY)
> > +
> > +#define set_gpfn_from_mfn(mfn, pfn) do { (void)(mfn), (void)(pfn);
> > } while (0)
> > +#define mfn_to_gfn(d, mfn) ((void)(d), _gfn(mfn_x(mfn)))
> > +
> > +#define PDX_GROUP_SHIFT (16 + 5)
> 
> Where are these magic numbers coming from? None of the other three
> architectures use literal numbers here, thus making clear what
> values are actually meant. If you can't use suitable constants,
> please add a comment.
This numbers are incorrect for RISC-V, it should be 12 + 9 ( PAGE_SHIFT
+ VPN_BITS ).
I did some comparision of how some macros are defined in PPC and missed
to update that.

~ Oleksii
Re: [PATCH v4 26/30] xen/riscv: add minimal stuff to mm.h to build full Xen
Posted by Jan Beulich 6 months, 3 weeks ago
On 16.02.2024 12:03, Oleksii wrote:
>>
>>> +        } free;
>>> +    } u;
>>> +
>>> +    union {
>>> +        /* Page is in use, but not as a shadow. */
>>
>> I'm also pretty sure I asked before what shadow this comment alludes
>> to.
> I missed your request about 'shadow' before.
> 
> The comment arrived from Arm.
> 
> I tried to find out the answer by investigation how 'inuse' is used,
> and, unfortunately, I couldn't find an answer what 'shadow' alludes to.

That's from x86'es shadow paging, where a page can serve as a "shadow" of
a guest page table page.

Jan