Re: [PATCH v7 12/12] powerpc/vas: Define copy/paste interfaces

Michael Ellerman [mpe@ellerman.id.au] wrote:

Hi Suka,

A few more things ...

Sukadev Bhattiprolu [off-list ref] writes:

quoted

diff --git a/arch/powerpc/platforms/powernv/copy-paste.h b/arch/powerpc/platforms/powernv/copy-paste.h
new file mode 100644
index 0000000..7783bb8
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/copy-paste.h

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2016 IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+/*
+ * Macros taken from tools/testing/selftests/powerpc/context_switch/cp_abort.c
+ */

These are both out of date, they're changed in v3.0B.

quoted

+#define PASTE(RA, RB, L, RC) \
+	.long (0x7c00070c | (RA) << (31-15) | (RB) << (31-20) \
+			  | (L) << (31-10) | (RC) << (31-31))

You should define PPC_PASTE() in ppc-opcode.h

We already have PPC_INST_PASTE, so use that.

L and RC are gone.

Ok. I thought they would come back later, but of course we can update
these kernel-only calls then.

quoted

+
+#define COPY(RA, RB, L) \
+	.long (0x7c00060c | (RA) << (31-15) | (RB) << (31-20) \
+			  | (L) << (31-10))

Use PPC_COPY().

Ok

quoted

+
+#define CR0_FXM		"0x80"

I don't think a #define for this helps readability.

quoted

+#define CR0_SHIFT	28
+#define CR0_MASK	0xF

Not used.

Will need them now to return value in cr0?

quoted

+/*
+ * Copy/paste instructions:
+ *
+ *	copy RA,RB,L
+ *		Copy contents of address (RA) + effective_address(RB)
+ *		to internal copy-buffer.
+ *
+ *		L == 1 indicates this is the first copy.
+ *
+ *		L == 0 indicates its a continuation of a prior first copy.
+ *
+ *	paste RA,RB,L
+ *		Paste contents of internal copy-buffer to the address
+ *		(RA) + effective_address(RB)
+ *
+ *		L == 0 indicates its a continuation of a prior paste. i.e.
+ *		don't wait for the completion or update status.
+ *
+ *		L == 1 indicates this is the last paste in the group (i.e.
+ *		wait for the group to complete and update status in CR0).
+ *
+ *	For Power9, the L bit must be 'true' in both copy and paste.
+ */
+
+static inline int vas_copy(void *crb, int offset, int first)
+{
+	WARN_ON_ONCE(!first);

Please change the API to not require unused parameters.

Same for offset.

Ok, Haren's NX patches will need to drop those parameters as well.

quoted

+
+	__asm__ __volatile(stringify_in_c(COPY(%0, %1, %2))";"

I've never seen __volatile before.

Just use: asm volatile

ok

quoted

+		:
+		: "b" (offset), "b" (crb), "i" (1)
+		: "memory");
+
+	return 0;
+}
+
+static inline int vas_paste(void *paste_address, int offset, int last)
+{
+	unsigned long long cr;

cr is 32-bits actually.

ok

quoted

+	WARN_ON_ONCE(!last);
+
+	cr = 0;
+	__asm__ __volatile(stringify_in_c(PASTE(%1, %2, 1, 1))";"
+		"mfocrf %0," CR0_FXM ";"
+		: "=r" (cr)
+		: "b" (paste_address), "b" (offset)
+		: "memory");

You need cr0 in the clobbers.

ok

quoted

+
+	return cr;

I think it would be more natural if you just returned CR0, so if you did
shift and mask with the CR0 constants you have above.

ok

quoted

diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
index 70762c3..73081b4 100644
--- a/arch/powerpc/platforms/powernv/vas-window.c
+++ b/arch/powerpc/platforms/powernv/vas-window.c

@@ -1040,6 +1041,57 @@ struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop,
 }
 EXPORT_SYMBOL_GPL(vas_tx_win_open);
 
+int vas_copy_crb(void *crb, int offset, bool first)
+{
+	if (!vas_initialized())
+		return -1;
+
+	return vas_copy(crb, offset, first);
+}
+EXPORT_SYMBOL_GPL(vas_copy_crb);
+
+#define RMA_LSMP_REPORT_ENABLE PPC_BIT(53)
+int vas_paste_crb(struct vas_window *txwin, int offset, bool last, bool re)
+{
+	int rc;
+	uint64_t val;
+	void *addr;
+
+	if (!vas_initialized())
+		return -1;

This is in the fast path, or at least the runtime path. So I don't think
these checks are wanted, how would we have got this far if vas wasn't
initialised?

Yes, I have dropped vas_initialized() now.

cheers