KY Srinivasan <kys@xxxxxxxxxxxxx> writes: >> -----Original Message----- >> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] >> Sent: Friday, April 7, 2017 4:27 AM >> To: devel@xxxxxxxxxxxxxxxxxxxxxx; x86@xxxxxxxxxx >> Cc: linux-kernel@xxxxxxxxxxxxxxx; KY Srinivasan <kys@xxxxxxxxxxxxx>; >> Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; Stephen Hemminger >> <sthemmin@xxxxxxxxxxxxx>; Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Ingo >> Molnar <mingo@xxxxxxxxxx>; H. Peter Anvin <hpa@xxxxxxxxx>; Steven >> Rostedt <rostedt@xxxxxxxxxxx>; Jork Loeser <Jork.Loeser@xxxxxxxxxxxxx> >> Subject: [PATCH 2/7] x86/hyper-v: fast hypercall implementation >> >> 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@xxxxxxxxxx> >> --- >> arch/x86/include/asm/mshyperv.h | 37 >> +++++++++++++++++++++++++++++++++++++ >> arch/x86/include/uapi/asm/hyperv.h | 19 +++++++++++++++++++ >> 2 files changed, 56 insertions(+) >> >> diff --git a/arch/x86/include/asm/mshyperv.h >> b/arch/x86/include/asm/mshyperv.h >> index 331e834..9a5f58b 100644 >> --- a/arch/x86/include/asm/mshyperv.h >> +++ b/arch/x86/include/asm/mshyperv.h >> @@ -216,6 +216,43 @@ 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}; > > Defining the hyper-call arguments on the stack can be problematic > if CONFIG_VMAP_STACK is defined - since we are passing the guest > physical address to the hypervisor, we cannot have the arguments > straddle a page boundary. > We have dealt with this issue currently by making sure the arguments are > never on the stack via different means. Perhaps, we can allocate memory > on a per-cpu basis that can be used for this purpose. In fact, this is what I have done > for the hv_post_message hypercall. We can just rename that page and use it in all > hypercalls - we can just allocate two pages on a per-CPU basis for this purpose > (for input and output parameters). This is fast hypercall and not the normal one - we pass control to register so we're fine here (and I'd actually expect the compiler to put it to the propper register in the first place. >> + >> + control.code = code; >> + control.fast = 1; >> +#ifdef CONFIG_X86_64 >> + { >> + u64 hv_status; >> + >> + __asm__ __volatile__("call *%3" >> + : "=a" (hv_status) >> + : "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; >> + >> + __asm__ __volatile__ ("call *%6" >> + : "=d"(hv_status_hi), >> + "=a"(hv_status_lo) : >> + "d" (control.as_uint32_hi), >> + "a" (control.as_uint32_lo), >> + "c" ((u32)input1), >> + "b" ((u32)(input1 >> 32)), >> + "m" (hv_hypercall_pg) >> + : "cc"); >> + >> + 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 >> -- >> 2.9.3 -- Vitaly _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
