linux-kernel - Re: [PATCH v4 05/15] x86/sev: Use kernel provided SVSM Calling Areas

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Message-ID: <20240506100905.GFZjisQTQwbkv2eKsh@fat_crate.local>
Date: Mon, 6 May 2024 12:09:05 +0200
From: Borislav Petkov <bp@...en8.de>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-coco@...ts.linux.dev, svsm-devel@...onut-svsm.dev,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Michael Roth <michael.roth@....com>,
	Ashish Kalra <ashish.kalra@....com>
Subject: Re: [PATCH v4 05/15] x86/sev: Use kernel provided SVSM Calling Areas

Ok,

I think this is very readable and clear what's going on:

static __always_inline void issue_svsm_call(struct svsm_call *call, u8 *pending)
{
        register unsigned long rax asm("rax") = call->rax;
        register unsigned long rcx asm("rcx") = call->rcx;
        register unsigned long rdx asm("rdx") = call->rdx;
        register unsigned long r8  asm("r8")  = call->r8;
        register unsigned long r9  asm("r9")  = call->r9;

        call->caa->call_pending = 1;

        asm volatile("rep; vmmcall\n\t"
                     : "+r" (rax), "+r" (rcx), "+r" (rdx), "+r" (r8), "+r" (r9));

        xchg(pending, 1);

        call->rax_out = rax;
        call->rcx_out = rcx;
        call->rdx_out = rdx;
        call->r8_out = r8;
        call->r9_out = r9;
}

and the asm looks ok but the devil's in the detail.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette