Re: [PATCHv4 2/2] arm64/io: Add a header for mmio access instrumentation

From: Sai Prakash Ranjan
Date: Thu Nov 18 2021 - 23:06:50 EST

Hi Arnd,

On 11/18/2021 8:54 PM, Arnd Bergmann wrote:
On Mon, Nov 15, 2021 at 12:33 PM Sai Prakash Ranjan
<quic_saipraka@xxxxxxxxxxx> wrote:
* Generic IO read/write. These perform native-endian accesses.
-#define __raw_writeb __raw_writeb
-static inline void __raw_writeb(u8 val, volatile void __iomem *addr)
+static inline void arch_raw_writeb(u8 val, volatile void __iomem *addr)
asm volatile("strb %w0, [%1]" : : "rZ" (val), "r" (addr));
Woundn't removing the #define here will break the logic in
making it fall back to the pointer-dereference version for the actual access?

#defines for these are added in mmio-instrumented.h header which is included in
arm64/asm/io.h, so it won't break the logic by falling back to pointer-dereference.

+void log_write_mmio(const char *width, volatile void __iomem *addr);
+void log_read_mmio(const char *width, const volatile void __iomem *addr);
+#define __raw_write(v, a, _l) ({ \
+ volatile void __iomem *_a = (a); \
+ if (tracepoint_enabled(rwmmio_write)) \
+ log_write_mmio(__stringify(write##_l), _a); \
+ arch_raw_write##_l((v), _a); \
+ })
This feels like it's getting too big to be inlined. Have you considered
integrating this with the lib/logic_iomem.c infrastructure instead?

That already provides a way to override MMIO areas, and it lets you do
the logging from a single place rather than having it duplicated in every
single caller. It also provides a way of filtering it based on the ioremap()

Thanks for the suggestion, will look at the logic_iomem.c and see if it fits our