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Date: Fri, 17 Mar 2017 12:33:47 +0100
From: Borislav Petkov <bp@suse.de>
Subject: Re: [RFC PATCH v2 14/32] x86: mm: Provide support to use memblock
 when spliting large pages
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>, simon.guinot@sequanux.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, rkrcmar@redhat.com, matt@codeblueprint.co.uk, linux-pci@vger.kernel.org, linus.walleij@linaro.org, gary.hook@amd.com, linux-mm@kvack.org, paul.gortmaker@windriver.com, hpa@zytor.com, cl@linux.com, dan.j.williams@intel.com, aarcange@redhat.com, sfr@canb.auug.org.au, andriy.shevchenko@linux.intel.com, herbert@gondor.apana.org.au, bhe@redhat.com, xemul@parallels.com, joro@8bytes.org, x86@kernel.org, peterz@infradead.org, piotr.luc@intel.com, mingo@redhat.com, msalter@redhat.com, ross.zwisler@linux.intel.com, dyoung@redhat.com, thomas.lendacky@amd.com, jroedel@suse.de, keescook@chromium.org, arnd@arndb.de, toshi.kani@hpe.com, mathieu.desnoyers@efficios.com, luto@kernel.org, devel@linuxdriverproject.org, bhelgaas@google.com, tglx@linutronix.de, mchehab@kernel.org

On Fri, Mar 17, 2017 at 12:03:31PM +0100, Paolo Bonzini wrote:

> If it is possible to do it in a fairly hypervisor-independent manner,
> I'm all for it.  That is, only by looking at AMD-specified CPUID leaves
> and at kernel ELF sections.

Not even that.

What that needs to be able to do is:

	kvm_map_percpu_hv_shared(st, sizeof(*st)))

where st is the percpu steal time ptr:

	struct kvm_steal_time *st = &per_cpu(steal_time, cpu);

Underneath, what it does basically is it clears the encryption mask from
the pte, see patch 16/32.

And I keep talking about SEV-ES because this is going to expand on the
need of having a shared memory region which the hypervisor and the guest
needs to access, thus unencrypted. See

http://support.amd.com/TechDocs/Protecting%20VM%20Register%20State%20with%20SEV-ES.pdf

This is where you come in and say what would be the best approach there...

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix ImendA?rffer, Jane Smithard, Graham Norton, HRB 21284 (AG NA 1/4 rnberg)
-- 

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