Hi kashyapc & all,
I see a piece of code in vmx_vcpu_run as below, is it used to switch
context to a guest? Kvm don't used "vmlaunch" or "vmresume" to launch or
resume a guest? Why does kvm need to manually switch context by filling
registers using stored register copies?
===============
asm(
/* Store host registers */
"push %%"R"dx; push %%"R"bp;"
"push %%"R"cx \n\t" /* placeholder for guest rcx */
"push %%"R"cx \n\t"
"cmp %%"R"sp, %c[host_rsp](%0) \n\t"
"je 1f \n\t"
"mov %%"R"sp, %c[host_rsp](%0) \n\t"
__ex(ASM_VMX_VMWRITE_RSP_RDX) "\n\t"
"1: \n\t"
/* Reload cr2 if changed */
"mov %c[cr2](%0), %%"R"ax \n\t"
"mov %%cr2, %%"R"dx \n\t"
"cmp %%"R"ax, %%"R"dx \n\t"
"je 2f \n\t"
"mov %%"R"ax, %%cr2 \n\t"
"2: \n\t"
/* Check if vmlaunch of vmresume is needed */
"cmpl $0, %c[launched](%0) \n\t"
/* Load guest registers. Don't clobber flags. */
"mov %c[rax](%0), %%"R"ax \n\t"
"mov %c[rbx](%0), %%"R"bx \n\t"
"mov %c[rdx](%0), %%"R"dx \n\t"
"mov %c[rsi](%0), %%"R"si \n\t"
"mov %c[rdi](%0), %%"R"di \n\t"
"mov %c[rbp](%0), %%"R"bp \n\t"
========
Thanks,
Zhengwang
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