[PATCH v4 04/10] x86/hyper-v: fast hypercall implementation

Vitaly Kuznetsov
2017-05-24T12:04:25Z

Hyper-V supports 'fast' hypercalls when all parameters are passed through
registers. Implement an inline version of a simpliest of these calls:
hypercall with one 8-byte input and no output.

Proper hypercall input interface (struct hv_hypercall_input) definition is
added as well.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Acked-by: K. Y. Srinivasan <kys@microsoft.com>
Tested-by: Simon Xiao <sixiao@microsoft.com>
Tested-by: Srikanth Myakam <v-srm@microsoft.com>
---
Change since v3:
- Force stack frame in hv_do_fast_hypercall8() [Andy Lutomirski]
---
arch/x86/include/asm/mshyperv.h | 41 ++++++++++++++++++++++++++++++++++++++
arch/x86/include/uapi/asm/hyperv.h | 19 ++++++++++++++++++
2 files changed, 60 insertions(+)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index cbbf7db..52b3611 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -217,6 +217,47 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
#endif /* !x86_64 */
}

+/* Fast hypercall with 8 bytes of input and no output */
+static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
+{
+ union hv_hypercall_input control = {0};
+ register void *__sp asm(_ASM_SP);
+
+ control.code = code;
+ control.fast = 1;
+#ifdef CONFIG_X86_64
+ {
+ u64 hv_status;
+
+ __asm__ __volatile__("call *%4"
+ : "=a" (hv_status), "+r" (__sp),
+ "+c" (control.as_uint64), "+d" (input1)
+ : "m" (hv_hypercall_pg)
+ : "cc", "r8", "r9", "r10", "r11");
+ return hv_status;
+ }
+#else
+ {
+ u32 hv_status_hi, hv_status_lo;
+ u32 input1_hi = (u32)(input1 >> 32);
+ u32 input1_lo = (u32)input1;
+
+ __asm__ __volatile__ ("call *%7"
+ : "=d"(hv_status_hi),
+ "=a"(hv_status_lo),
+ "+c"(input1_lo),
+ "+r"(__sp)
+ : "d" (control.as_uint32_hi),
+ "a" (control.as_uint32_lo),
+ "b" (input1_hi),
+ "m" (hv_hypercall_pg)
+ : "cc", "edi", "esi");
+
+ return hv_status_lo | ((u64)hv_status_hi << 32);
+ }
+#endif
+}
+
void hyperv_init(void);
void hyperv_report_panic(struct pt_regs *regs);
bool hv_is_hypercall_page_setup(void);
diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 432df4b..c87e900 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -256,6 +256,25 @@
#define HV_PROCESSOR_POWER_STATE_C2 2
#define HV_PROCESSOR_POWER_STATE_C3 3

+/* Hypercall interface */
+union hv_hypercall_input {
+ u64 as_uint64;
+ struct {
+ __u32 as_uint32_lo;
+ __u32 as_uint32_hi;
+ };
+ struct {
+ __u64 code:16;
+ __u64 fast:1;
+ __u64 varhead_size:10;
+ __u64 reserved1:5;
+ __u64 rep_count:12;
+ __u64 reserved2:4;
+ __u64 rep_start:12;
+ __u64 reserved3:4;
+ };
+};
+
/* hypercall status code */
#define HV_STATUS_SUCCESS 0
#define HV_STATUS_INVALID_HYPERCALL_CODE 2
--
2.9.4