Messages in this thread | | | Date | Sun, 1 Nov 2015 12:51:09 -0800 | Subject | Re: [GIT PULL] memremap fix for 4.3 (v2) | From | Dan Williams <> |
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On Sun, Nov 1, 2015 at 12:36 PM, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote: > On Sun, Nov 01, 2015 at 08:24:25PM +0000, Williams, Dan J wrote: >> diff --git a/kernel/memremap.c b/kernel/memremap.c >> index 72b0c66628b6..9d6b55587eaa 100644 >> --- a/kernel/memremap.c >> +++ b/kernel/memremap.c >> @@ -24,6 +24,16 @@ __weak void __iomem *ioremap_cache(resource_size_t offset, unsigned long size) >> } >> #endif >> >> +static void *try_ram_remap(resource_size_t offset, size_t size) >> +{ >> + struct page *page = pfn_to_page(offset >> PAGE_SHIFT); >> + >> + /* In the simple case just return the existing linear address */ >> + if (!PageHighMem(page)) >> + return __va(offset); >> + return NULL; /* fallback to ioremap_cache */ > > Right, so a highmem page results in this returning NULL, which will... > >> @@ -66,8 +76,8 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags) >> * the requested range is potentially in "System RAM" >> */ >> if (is_ram == REGION_INTERSECTS) >> - addr = __va(offset); >> - else >> + addr = try_ram_remap(offset, size); >> + if (!addr) >> addr = ioremap_cache(offset, size); > > cause ioremap_cache() to be called. That falls through on ARM to: > > __arm_ioremap_pfn_caller() > > and we will hit this (as I've mentioned before through explanation > rather than quoting code): > > /* > * Don't allow RAM to be mapped - this causes problems with ARMv6+ > */ > if (WARN_ON(pfn_valid(pfn))) > return NULL; >
Right, which means the caller is broken and shouldn't be using memremap, same as misuse of ioremap_cache today.
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