Add slow_virt_to_phys() function for ARM64 that parallels the same
function on x86/x64. This is needed by the architecture independent
Hyper-V VMbus driver at drivers/hv/channel.c. The implementation
directly translates the virtual address using the ARM64 'at'
instruction.
Signed-off-by: Michael Kelley <mikel...@microsoft.com>
Reviewed-by: James Morris <james.mor...@microsoft.com>
---
arch/arm64/include/asm/memory.h | 6 ++++++
arch/arm64/mm/pageattr.c | 37 +++++++++++++++++++++++++++++++++++++
2 files changed, 43 insertions(+)
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 49d9921..3f68dcf 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -265,6 +265,12 @@ static inline void *phys_to_virt(phys_addr_t x)
}
/*
+ * For memory where the underlying physical pages may not
+ * be contiguous.
+ */
+extern phys_addr_t slow_virt_to_phys(void *vaddr);
+
+/*
* Drivers should NOT use these either.
*/
#define __pa(x) __virt_to_phys((unsigned long)(x))
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index a563593..8a42cac 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -19,6 +19,8 @@
#include <asm/pgtable.h>
#include <asm/set_memory.h>
#include <asm/tlbflush.h>
+#include <asm/sysreg.h>
+#include <asm/barrier.h>
struct page_change_data {
pgprot_t set_mask;
@@ -185,3 +187,38 @@ bool kernel_page_present(struct page *page)
}
#endif /* CONFIG_HIBERNATION */
#endif /* CONFIG_DEBUG_PAGEALLOC */
+
+/*
+ * For virtual addresses where the underlyine physical memory may not be
+ * contiguous and the normal virt_to_phys gives the wrong result. This
+ * function does an actual translation using the 'at' instruction.
+ */
+phys_addr_t slow_virt_to_phys(void *virt_addr)
+{
+ phys_addr_t result;
+ unsigned long input = (unsigned long)virt_addr;
+ char touch;
+ int i;
+
+ /* Try up to 3 times (an arbitrary number) */
+ for (i = 0; i < 3; i++) {
+ /* Do the translation and check that it worked */
+ asm volatile("at s1e1r, %0" : : "r" (input));
+ isb();
+ result = read_sysreg(par_el1);
+ if (likely(!(result & 0x1)))
+ return (result & GENMASK_ULL(51, 12)) |
+ (input & GENMASK_ULL(11, 0));
+ /*
+ * Something failed. Read the page to fault in anything
+ * that isn't resident, then try again. "Anything"
+ * could include the page itself or hypervisor page tables.
+ */
+ touch = READ_ONCE(*(char *)input);
+ dmb(sy);
+ }
+
+ /* Let the caller sort it out. */
+ return -1;
+}
+EXPORT_SYMBOL_GPL(slow_virt_to_phys);
--
1.8.3.1
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