linux-kernel - Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted

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Message-ID: <20230309144505.GEZAnw8QpyOyMpCD4r@fat_crate.local>
Date:   Thu, 9 Mar 2023 15:45:05 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Jörg Rödel <joro@...tes.org>
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Dave Hansen <dave.hansen@...el.com>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
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        "hpa@...or.com" <hpa@...or.com>, KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
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        "peterz@...radead.org" <peterz@...radead.org>,
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        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
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        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>
Subject: Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range
 to map as encrypted

On Thu, Mar 09, 2023 at 03:36:45PM +0100, Jörg Rödel wrote:
> Yes, that is right. The key is mainly for the NMI entry path which can
> be performance relevant in some situations. For SEV-ES some special
> handling is needed there to re-enable NMIs and adjust the #VC stack in
> case it was raised on the VC-handlers entry path.

So the performance argument is meh. That key will be replaced by

	if (cc_vendor == CC_VENDOR_AMD &&
	    cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)

which is something like 4 insns or so. Tops.

Haven't looked yet but it should be cheap.

-- 
Regards/Gruss,
    Boris.

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