Re: [PATCH v4 15/46] KVM: PPC: Book3S 64: Move hcall early register setup to KVM
From: Paul Mackerras <hidden>
Date: 2021-04-01 05:42:17
On Tue, Mar 23, 2021 at 11:02:34AM +1000, Nicholas Piggin wrote:
System calls / hcalls have a different calling convention than other interrupts, so there is code in the KVMTEST to massage these into the same form as other interrupt handlers. Move this work into the KVM hcall handler. This means teaching KVM a little more about the low level interrupt handler setup, PACA save areas, etc., although that's not obviously worse than the current approach of coming up with an entirely different interrupt register / save convention.
[snip]
quoted hunk ↗ jump to hunk
@@ -1964,29 +1948,8 @@ EXC_VIRT_END(system_call, 0x4c00, 0x100) #ifdef CONFIG_KVM_BOOK3S_64_HANDLER TRAMP_REAL_BEGIN(system_call_kvm) - /* - * This is a hcall, so register convention is as above, with these - * differences:
I haven't checked all the code changes in detail yet, but this comment at least is slightly misleading, since under PR KVM, system calls (to the guest kernel) and hypercalls both come through this path. Paul.