Re: [RFC PATCH V6 02/14] x86/sev: Add Check of #HV event in path

[Tianyu Lan]

On 5/16/2023 5:32 PM, Peter Zijlstra wrote:
> > --- a/arch/x86/entry/entry_64.S
> > +++ b/arch/x86/entry/entry_64.S
> > @@ -1019,6 +1019,15 @@ SYM_CODE_END(paranoid_entry)
> >    * R15 - old SPEC_CTRL
> >    */
> >   SYM_CODE_START_LOCAL(paranoid_exit)
> > +#ifdef CONFIG_AMD_MEM_ENCRYPT
> > +	/*
> > +	 * If a #HV was delivered during execution and interrupts were
> > +	 * disabled, then check if it can be handled before the iret
> > +	 * (which may re-enable interrupts).
> > +	 */
> > +	mov     %rsp, %rdi
> > +	call    check_hv_pending
> > +#endif
> >   	UNWIND_HINT_REGS
> >   
> >   	/*
> > @@ -1143,6 +1152,15 @@ SYM_CODE_START(error_entry)
> >   SYM_CODE_END(error_entry)
> >   
> >   SYM_CODE_START_LOCAL(error_return)
> > +#ifdef CONFIG_AMD_MEM_ENCRYPT
> > +	/*
> > +	 * If a #HV was delivered during execution and interrupts were
> > +	 * disabled, then check if it can be handled before the iret
> > +	 * (which may re-enable interrupts).
> > +	 */
> > +	mov     %rsp, %rdi
> > +	call    check_hv_pending
> > +#endif
> >   	UNWIND_HINT_REGS
> >   	DEBUG_ENTRY_ASSERT_IRQS_OFF
> >   	testb	$3, CS(%rsp)
> Oh hell no... do now you're adding unconditional calls to every single
> interrupt and nmi exit path, with the grand total of 0 justification.

Sorry to Add check inside of check_hv_pending(). Will move the check 
before calling check_hv_pending() in the next version. Thanks.