diff mbox series

[v2,03/11] arm64: gunyah: Add Gunyah hypercalls ABI

Message ID 20220801211240.597859-4-quic_eberman@quicinc.com
State New
Headers show
Series Drivers for gunyah hypervisor | expand

Commit Message

Elliot Berman Aug. 1, 2022, 9:12 p.m. UTC 
Add initial support to perform Gunyah hypercalls. The arm64 ABI for
Gunyah hypercalls generally follows the SMC Calling Convention.

Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
---
 MAINTAINERS                     |   1 +
 arch/arm64/include/asm/gunyah.h | 134 ++++++++++++++++++++++++++++++++
 2 files changed, 135 insertions(+)
 create mode 100644 arch/arm64/include/asm/gunyah.h

Comments

Dmitry Baryshkov Aug. 2, 2022, 1:34 p.m. UTC | #1 
On 02/08/2022 00:12, Elliot Berman wrote:
> Add initial support to perform Gunyah hypercalls. The arm64 ABI for
> Gunyah hypercalls generally follows the SMC Calling Convention.

Seeing a c&p (or c&rework) from arm-smccc.h, could you please describe:

1) Why can't you use the existing arm_smccc_1_1_hvc()? I checked, you 
don't seem to be getting more than 4 values back.

2) If #1 is not possible, why can't you add necessary glue code to the 
arm-smccc.h (as your code to support nargs/multiple return values is 
generic enough) and use corresponding macro in asm/gunyah.h ?
Elliot Berman Aug. 3, 2022, 9:15 p.m. UTC | #2 
Hi Dmitry,

On 8/2/2022 6:34 AM, Dmitry Baryshkov wrote:
> On 02/08/2022 00:12, Elliot Berman wrote:
>> Add initial support to perform Gunyah hypercalls. The arm64 ABI for
>> Gunyah hypercalls generally follows the SMC Calling Convention.
> 
> Seeing a c&p (or c&rework) from arm-smccc.h, could you please describe:
> 
> 1) Why can't you use the existing arm_smccc_1_1_hvc()? I checked, you 
> don't seem to be getting more than 4 values back.
> 

The Gunyah APIs can return up to 8 values. As you observed though, these 
initial patches are only using the first 4 values back. I'd like to use 
the larger v1.2 so I don't need to update later.

> 2) If #1 is not possible, why can't you add necessary glue code to the 
> arm-smccc.h (as your code to support nargs/multiple return values is 
> generic enough) and use corresponding macro in asm/gunyah.h ?
> 

I think the code here may be considered Gunyah-specific as I am limiting 
to 8 arguments and return values. If I add to arm-smccc.h, I would need 
to expand out to x17. Does it make sense to add another SMCCC 1.2 
interface to arm-smccc.h?
Dmitry Baryshkov Aug. 4, 2022, 7:04 a.m. UTC | #3 
On Thu, 4 Aug 2022 at 00:15, Elliot Berman <quic_eberman@quicinc.com> wrote:
>
> Hi Dmitry,
>
> On 8/2/2022 6:34 AM, Dmitry Baryshkov wrote:
> > On 02/08/2022 00:12, Elliot Berman wrote:
> >> Add initial support to perform Gunyah hypercalls. The arm64 ABI for
> >> Gunyah hypercalls generally follows the SMC Calling Convention.
> >
> > Seeing a c&p (or c&rework) from arm-smccc.h, could you please describe:
> >
> > 1) Why can't you use the existing arm_smccc_1_1_hvc()? I checked, you
> > don't seem to be getting more than 4 values back.
> >
>
> The Gunyah APIs can return up to 8 values. As you observed though, these
> initial patches are only using the first 4 values back. I'd like to use
> the larger v1.2 so I don't need to update later.

I'd suggest following the hyperv example here. It uses arm_smccc_1_1
when possible and 1_2 only when required. Note, that if you are using
the 1_2 call all the times, you are somewhat wasting the cpu cycles by
always copying x0...x17 instead of just x0...x3.

> > 2) If #1 is not possible, why can't you add necessary glue code to the
> > arm-smccc.h (as your code to support nargs/multiple return values is
> > generic enough) and use corresponding macro in asm/gunyah.h ?
> >
>
> I think the code here may be considered Gunyah-specific as I am limiting
> to 8 arguments and return values. If I add to arm-smccc.h, I would need
> to expand out to x17. Does it make sense to add another SMCCC 1.2
> interface to arm-smccc.h?

You do not need to handle 8 arguments at this moment, until the moment
you really need this code, I'd suggest postponing this change. And
when you need it, having the generic code is better than having the
gh-specific code.
diff mbox series

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index 0cd12ea6c11c..02f97ac90cdf 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8743,6 +8743,7 @@  L:	linux-arm-msm@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
 F:	Documentation/virt/gunyah/
+F:	arch/arm64/include/asm/gunyah.h
 
 HABANALABS PCI DRIVER
 M:	Oded Gabbay <ogabbay@kernel.org>
diff --git a/arch/arm64/include/asm/gunyah.h b/arch/arm64/include/asm/gunyah.h
new file mode 100644
index 000000000000..4820e9389f40
--- /dev/null
+++ b/arch/arm64/include/asm/gunyah.h
@@ -0,0 +1,134 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+#ifndef __ASM_GUNYAH_H
+#define __ASM_GUNYAH_H
+
+#include <linux/arm-smccc.h>
+#include <linux/types.h>
+
+#define GH_CALL_TYPE_PLATFORM_CALL		0
+#define GH_CALL_TYPE_HYPERCALL			2
+#define GH_CALL_TYPE_SERVICE			3
+#define GH_CALL_TYPE_SHIFT			14
+#define GH_CALL_FUNCTION_NUM_MASK		0x3fff
+
+#define GH_SERVICE(fn)		ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, \
+						   ARM_SMCCC_OWNER_VENDOR_HYP, \
+						   (GH_CALL_TYPE_SERVICE << GH_CALL_TYPE_SHIFT) \
+							| ((fn) & GH_CALL_FUNCTION_NUM_MASK))
+
+#define GH_HYPERCALL(fn)	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_64, \
+						   ARM_SMCCC_OWNER_VENDOR_HYP, \
+						   (GH_CALL_TYPE_HYPERCALL << GH_CALL_TYPE_SHIFT) \
+							| ((fn) & GH_CALL_FUNCTION_NUM_MASK))
+
+#define ___gh_count_args(_0, _1, _2, _3, _4, _5, _6, _7, _8, x, ...) x
+
+#define __gh_count_args(...)						\
+	___gh_count_args(_, ## __VA_ARGS__, 8, 7, 6, 5, 4, 3, 2, 1, 0)
+
+#define __gh_skip_0(...)		__VA_ARGS__
+#define __gh_skip_1(a, ...)	__VA_ARGS__
+#define __gh_skip_2(a, b, ...)	__VA_ARGS__
+#define __gh_skip_3(a, b, c, ...)	__VA_ARGS__
+#define __gh_skip_4(a, b, c, d, ...)	__VA_ARGS__
+#define __gh_skip_5(a, b, c, d, e, ...)	__VA_ARGS__
+#define __gh_skip_6(a, b, c, d, e, f, ...)	__VA_ARGS__
+#define __gh_skip_7(a, b, c, d, e, f, g, ...)	__VA_ARGS__
+#define __gh_skip_8(a, b, c, d, e, f, g, h, ...)	__VA_ARGS__
+#define __gh_to_res(nargs, ...)		__gh_skip_ ## nargs (__VA_ARGS__)
+
+#define __gh_declare_arg_0(...)
+
+#define __gh_declare_arg_1(arg1, ...)						\
+	.a1 = (arg1)
+
+#define __gh_declare_arg_2(arg1, arg2, ...)					\
+	__gh_declare_arg_1(arg1),						\
+	.a2 = (arg2)
+
+#define __gh_declare_arg_3(arg1, arg2, arg3, ...)				\
+	__gh_declare_arg_2(arg1, arg2),						\
+	.a3 = (arg3)
+
+#define __gh_declare_arg_4(arg1, arg2, arg3, arg4, ...)				\
+	__gh_declare_arg_3(arg1, arg2, arg3),					\
+	.a4 = (arg4)
+
+#define __gh_declare_arg_5(arg1, arg2, arg3, arg4, arg5, ...)			\
+	__gh_declare_arg_4(arg1, arg2, arg3, arg4),				\
+	.a5 = (arg5)
+
+#define __gh_declare_arg_6(arg1, arg2, arg3, arg4, arg5, arg6, ...)		\
+	__gh_declare_arg_5(arg1, arg2, arg3, arg4, arg5),			\
+	.a6 = (arg6)
+
+#define __gh_declare_arg_7(arg1, arg2, arg3, arg4, arg5, arg6, arg7, ...)	\
+	__gh_declare_arg_6(arg1, arg2, arg3, arg4, arg5, arg6),			\
+	.a7 = (arg7)
+
+#define __gh_declare_arg_8(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, ...)	\
+	__gh_declare_arg_7(arg1, arg2, arg3, arg4, arg5, arg6, arg7),		\
+	.a8 = (arg8)
+
+#define ___gh_declare_args(nargs)	__gh_declare_arg_ ## nargs
+#define __gh_declare_args(nargs)	___gh_declare_args(nargs)
+#define _gh_declare_args(nargs, ...) __gh_declare_args(nargs)(__VA_ARGS__)
+
+#define __gh_assign_res_0(...)
+
+#define __gh_assign_res_1(r1)					\
+	r1 = __res.a0
+
+#define __gh_assign_res_2(r1, r2)				\
+	__gh_assign_res_1(r1);					\
+	r2 = __res.a1
+
+#define __gh_assign_res_3(r1, r2, r3)				\
+	__gh_assign_res_2(r1, r2);				\
+	r3 = __res.a2
+
+#define __gh_assign_res_4(r1, r2, r3, r4)			\
+	__gh_assign_res_3(r1, r2, r3);				\
+	r4 = __res.a3
+
+#define __gh_assign_res_5(r1, r2, r3, r4, r5)			\
+	__gh_assign_res_4(r1, r2, r3, r4);			\
+	r5 = __res.a4
+
+#define __gh_assign_res_6(r1, r2, r3, r4, r5, r6)		\
+	__gh_assign_res_5(r1, r2, r3, r4, r5);			\
+	r6 = __res.a5
+
+#define __gh_assign_res_7(r1, r2, r3, r4, r5, r6, r7)		\
+	__gh_assign_res_6(r1, r2, r3, r4, r5, r6);		\
+	r7 = __res.a6
+
+#define __gh_assign_res_8(r1, r2, r3, r4, r5, r6, r7, r8)	\
+	__gh_assign_res_7(r1, r2, r3, r4, r5, r6, r7);		\
+	r8 = __res.a7
+
+#define ___gh_assign_res(nargs)	__gh_assign_res_ ## nargs
+#define __gh_assign_res(nargs)	___gh_assign_res(nargs)
+#define _gh_assign_res(...) __gh_assign_res(__gh_count_args(__VA_ARGS__))(__VA_ARGS__)
+
+/**
+ * arch_gh_hypercall() - Performs an AArch64-specific call into hypervisor using Gunyah ABI
+ * @hcall_num: Hypercall function ID to invoke
+ * @nargs: Number of input arguments
+ * @...: First nargs are the input arguments. Remaining arguments are output variables.
+ */
+#define arch_gh_hypercall(hcall_num, nargs, ...)				\
+	do {									\
+		struct arm_smccc_1_2_regs __res;					\
+		struct arm_smccc_1_2_regs __args = {				\
+			.a0 = hcall_num,					\
+			_gh_declare_args(nargs, __VA_ARGS__)			\
+		};								\
+		arm_smccc_1_2_hvc(&__args, &__res);					\
+		_gh_assign_res(__gh_to_res(nargs, __VA_ARGS__));		\
+	} while (0)
+
+#endif