linux-kernel - Re: [PATCH v6 42/76] x86/sev-es: Setup early #VC handler

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Message-ID: <CAJhGHyA-GXrBgOxEu0sqN_+LMd7qUot=_2J1g6yGTvo-Mei6xA@mail.gmail.com>
Date:   Sat, 4 Sep 2021 17:39:41 +0800
From:   Lai Jiangshan <jiangshanlai+lkml@...il.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     X86 ML <x86@...nel.org>, Joerg Roedel <jroedel@...e.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Martin Radev <martin.b.radev@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v6 42/76] x86/sev-es: Setup early #VC handler

> @@ -363,6 +370,33 @@ SYM_CODE_START_LOCAL(early_idt_handler_common)
>         jmp restore_regs_and_return_to_kernel
>  SYM_CODE_END(early_idt_handler_common)
>
> +#ifdef CONFIG_AMD_MEM_ENCRYPT
> +/*
> + * VC Exception handler used during very early boot. The
> + * early_idt_handler_array can't be used because it returns via the
> + * paravirtualized INTERRUPT_RETURN and pv-ops don't work that early.

Hello Joerg, Juergen

The commit ae755b5a4548 ("x86/paravirt: Switch iret pvops to ALTERNATIVE")
( https://lore.kernel.org/lkml/20210311142319.4723-12-jgross@suse.com/ )
had been merged and the paravirt_iret is deferenced based via %rip.

Can INTERRUPT_RETURN still be a problem if early_idt_handler_array
is used instead for bringup IDT?

Thanks
Lai