Re: [PATCH 09/17] powerpc: make __ioremap_caller() common to PPC32 and PPC64

From: Christophe LEROY
Date: Wed May 16 2018 - 05:25:30 EST



Le 08/05/2018 Ã 11:56, Aneesh Kumar K.V a ÃcritÂ:
Christophe Leroy <christophe.leroy@xxxxxx> writes:

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
---
arch/powerpc/include/asm/book3s/64/pgtable.h | 1 +
arch/powerpc/mm/ioremap.c | 126 +++++++--------------------
2 files changed, 34 insertions(+), 93 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index c5c6ead06bfb..2bebdd8302cb 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -18,6 +18,7 @@
#define _PAGE_RO 0
#define _PAGE_USER 0
#define _PAGE_HWWRITE 0
+#define _PAGE_COHERENT 0

This is something I was trying to avoid when I split the headers. We do
support _PAGE_USER it is !_PAGE_PRIVILEGED. It gets really confusing
when we have these conflicting names because we are trying to make code
common across platforms.

Euh ... Here patch adds _PAGE_COHERENT

_PAGE_USER was added some time ago.

Well, we have three cases:

BOOK3S64 and NOHASH32/8xx has _PAGE_PRIVILEGED and no _PAGE_USER
BOOKE has both _PAGE_PRIVILEGED and _PAGE_USER
Others have _PAGE_USER and no _PAGE_PRIVILEGED

So when giving user rights to a page, some will set _PAGE_USER, some will unset _PAGE_PRIVILEGED and some will do both.

_PAGE_USER and _PAGE_PRIVILEGED being used outside of the subarch headers,
- either we have to add uggly ifdefs
- or we can just make sure unused flags are set as 0, then (x | 0) and (x & ~0) will do nothing and will be eliminated by the compiler.

Today, this is done in asm/pte-common.h. Unfortunately, all headers except book3s64 do include pte-common.

Another solution would be to make sure _PAGE_xxx flags are not used outside of subarch specific headers. That would mean having specific helpers defined in each subarch header, but is it really worth it ?




Lets take the exemple of an even more tricky one :
- Some subarchs have _PAGE_RW, others have _PAGE_RO instead. In addition, the 8xx has _PAGE_NA
- Book3s64 has _PAGE_READ and _PAGE_WRITE.
- In some places, _PAGE_RW has been redefined has _PAGE_READ | _PAGE_WRITE

It has really become pretty complex. Why having defined new flags instead of using _PAGE_RO for _PAGE_READ and _PAGE_RW for _PAGE_READ | _PAGE_WRITE ? Does it make any sense to have the possibility to set _PAGE_WRITE without _PAGE_READ ?


I feel like having simple generic code like:

flags = (flags & ~_PAGE_PRIVILEGED) | _PAGE_USER;

is better than having almost same code duplicated in several places or ugly ifdefs like:

#if defined(CONFIG_BOOK3S64) || defined(CONFIG_PPC_8xx) || defined (CONFIG_BOOKE)
flags &= ~_PAGE_PRIVILEGED;
#endif
#if !defined(CONFIG_BOOK3S64) && !defined(CONFIG_PPC_8xx)
flags |= _PAGE_USER;
#endif


It looks to me that patch https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=812fadcb941a81d1f3948b10a95a4dce663da3e4 allowed a nice code simplification, don't you feel the same ?

Christophe



#define _PAGE_EXEC 0x00001 /* execute permission */
#define _PAGE_WRITE 0x00002 /* write access allowed */
diff --git a/arch/powerpc/mm/ioremap.c b/arch/powerpc/mm/ioremap.c
index 65d611d44d38..59be5dfcb3e9 100644
--- a/arch/powerpc/mm/ioremap.c
+++ b/arch/powerpc/mm/ioremap.c
@@ -33,95 +33,6 @@ unsigned long ioremap_bot;
unsigned long ioremap_bot = IOREMAP_BASE;
#endif
-#ifdef CONFIG_PPC32
-
-void __iomem *
-__ioremap_caller(phys_addr_t addr, unsigned long size, unsigned long flags,
- void *caller)
-{
- unsigned long v, i;
- phys_addr_t p;
- int err;
-
- /* Make sure we have the base flags */
- if ((flags & _PAGE_PRESENT) == 0)
- flags |= pgprot_val(PAGE_KERNEL);
-
- /* Non-cacheable page cannot be coherent */
- if (flags & _PAGE_NO_CACHE)
- flags &= ~_PAGE_COHERENT;
-
- /*
- * Choose an address to map it to.
- * Once the vmalloc system is running, we use it.
- * Before then, we use space going up from IOREMAP_BASE
- * (ioremap_bot records where we're up to).
- */
- p = addr & PAGE_MASK;
- size = PAGE_ALIGN(addr + size) - p;
-
- /*
- * If the address lies within the first 16 MB, assume it's in ISA
- * memory space
- */
- if (p < 16*1024*1024)
- p += _ISA_MEM_BASE;
-
-#ifndef CONFIG_CRASH_DUMP
- /*
- * Don't allow anybody to remap normal RAM that we're using.
- * mem_init() sets high_memory so only do the check after that.
- */
- if (slab_is_available() && (p < virt_to_phys(high_memory)) &&
- page_is_ram(__phys_to_pfn(p))) {
- printk("__ioremap(): phys addr 0x%llx is RAM lr %ps\n",
- (unsigned long long)p, __builtin_return_address(0));
- return NULL;
- }
-#endif
-
- if (size == 0)
- return NULL;
-
- /*
- * Is it already mapped? Perhaps overlapped by a previous
- * mapping.
- */
- v = p_block_mapped(p);
- if (v)
- goto out;
-
- if (slab_is_available()) {
- struct vm_struct *area;
- area = get_vm_area_caller(size, VM_IOREMAP, caller);
- if (area == 0)
- return NULL;
- area->phys_addr = p;
- v = (unsigned long) area->addr;
- } else {
- v = ioremap_bot;
- ioremap_bot += size;
- }
-
- /*
- * Should check if it is a candidate for a BAT mapping
- */
-
- err = 0;
- for (i = 0; i < size && err == 0; i += PAGE_SIZE)
- err = map_kernel_page(v+i, p+i, flags);
- if (err) {
- if (slab_is_available())
- vunmap((void *)v);
- return NULL;
- }
-
-out:
- return (void __iomem *) (v + ((unsigned long)addr & ~PAGE_MASK));
-}
-
-#else
-
/**
* __ioremap_at - Low level function to establish the page tables
* for an IO mapping
@@ -135,6 +46,10 @@ void __iomem * __ioremap_at(phys_addr_t pa, void *ea, unsigned long size,
if ((flags & _PAGE_PRESENT) == 0)
flags |= pgprot_val(PAGE_KERNEL);
+ /* Non-cacheable page cannot be coherent */
+ if (flags & _PAGE_NO_CACHE)
+ flags &= ~_PAGE_COHERENT;
+
/* We don't support the 4K PFN hack with ioremap */
if (flags & H_PAGE_4K_PFN)
return NULL;
@@ -187,6 +102,33 @@ void __iomem * __ioremap_caller(phys_addr_t addr, unsigned long size,
if ((size == 0) || (paligned == 0))
return NULL;
+ /*
+ * If the address lies within the first 16 MB, assume it's in ISA
+ * memory space
+ */
+ if (IS_ENABLED(CONFIG_PPC32) && paligned < 16*1024*1024)
+ paligned += _ISA_MEM_BASE;
+
+ /*
+ * Don't allow anybody to remap normal RAM that we're using.
+ * mem_init() sets high_memory so only do the check after that.
+ */
+ if (!IS_ENABLED(CONFIG_CRASH_DUMP) &&
+ slab_is_available() && (paligned < virt_to_phys(high_memory)) &&
+ page_is_ram(__phys_to_pfn(paligned))) {
+ printk("__ioremap(): phys addr 0x%llx is RAM lr %ps\n",
+ (u64)paligned, __builtin_return_address(0));
+ return NULL;
+ }
+
+ /*
+ * Is it already mapped? Perhaps overlapped by a previous
+ * mapping.
+ */
+ ret = (void __iomem *)p_block_mapped(paligned);
+ if (ret)
+ goto out;
+
if (slab_is_available()) {
struct vm_struct *area;
@@ -205,14 +147,12 @@ void __iomem * __ioremap_caller(phys_addr_t addr, unsigned long size,
if (ret)
ioremap_bot += size;
}
-
+out:
if (ret)
- ret += addr & ~PAGE_MASK;
+ ret += (unsigned long)addr & ~PAGE_MASK;
return ret;
}
-#endif
-
/*
* Unmap an IO region and remove it from imalloc'd list.
* Access to IO memory should be serialized by driver.
--
2.13.3