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Date: Tue, 20 Oct 2020 09:38:09 +0800 From: Shuo A Liu <shuo.a.liu@...el.com> To: Arvind Sankar <nivedita@...m.mit.edu> Cc: linux-kernel@...r.kernel.org, x86@...nel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "H . Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Sean Christopherson <sean.j.christopherson@...el.com>, Yu Wang <yu1.wang@...el.com>, Reinette Chatre <reinette.chatre@...el.com>, Yakui Zhao <yakui.zhao@...el.com>, Dave Hansen <dave.hansen@...el.com>, Dan Williams <dan.j.williams@...el.com>, Fengwei Yin <fengwei.yin@...el.com>, Zhi Wang <zhi.a.wang@...el.com>, Zhenyu Wang <zhenyuw@...ux.intel.com>, Peter Zijlstra <peterz@...radead.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Segher Boessenkool <segher@...nel.crashing.org> Subject: Re: [PATCH v5 04/17] x86/acrn: Introduce hypercall interfaces On Mon 19.Oct'20 at 18:15:15 -0400, Arvind Sankar wrote: >On Mon, Oct 19, 2020 at 02:17:50PM +0800, shuo.a.liu@...el.com wrote: >> From: Shuo Liu <shuo.a.liu@...el.com> >> >> The Service VM communicates with the hypervisor via conventional >> hypercalls. VMCALL instruction is used to make the hypercalls. >> >> ACRN hypercall ABI: >> * Hypercall number is in R8 register. >> * Up to 2 parameters are in RDI and RSI registers. >> * Return value is in RAX register. >> >> Introduce the ACRN hypercall interfaces. Because GCC doesn't support R8 >> register as direct register constraints, use supported constraint as >> input with a explicit MOV to R8 in beginning of asm. >> >> +static inline long acrn_hypercall0(unsigned long hcall_id) >> +{ >> + long result; >> + >> + asm volatile("movl %1, %%r8d\n\t" >> + "vmcall\n\t" >> + : "=a" (result) >> + : "ir" (hcall_id) > >Is the hypercall id an unsigned long (64 bits) or an unsigned int (32 >bits)? This will generate broken assembly if the "r" option is chosen, >eg something like > movl %rdi, %r8d Yes, it can be an unsigned long. So do MOV explicitly. asm volatile("movq %1, %%r8\n\t" "vmcall\n\t" : "=a" (result) : "ir" (hcall_id) Thanks
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