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From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Tom Lendacky <thomas.lendacky@amd.com>
Cc: "Kuppuswamy,
	Sathyanarayanan"  <sathyanarayanan.kuppuswamy@linux.intel.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
	iommu@lists.linux-foundation.org, kvm@vger.kernel.org,
	linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
	linux-graphics-maintainer@vmware.com,
	amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org,
	Borislav Petkov <bp@alien8.de>,
	Brijesh Singh <brijesh.singh@amd.com>,
	Joerg Roedel <joro@8bytes.org>, Andi Kleen <ak@linux.intel.com>,
	Tianyu Lan <Tianyu.Lan@microsoft.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Will Deacon <will@kernel.org>, Dave Young <dyoung@redhat.com>,
	Baoquan He <bhe@redhat.com>
Subject: Re: [PATCH 07/11] treewide: Replace the use of mem_encrypt_active() with prot_guest_has()
Date: Wed, 11 Aug 2021 15:19:17 +0300	[thread overview]
Message-ID: <20210811121917.ghxi7g4mctuybhbk@box.shutemov.name> (raw)
In-Reply-To: <4b885c52-f70a-147e-86bd-c71a8f4ef564@amd.com>

On Tue, Aug 10, 2021 at 02:48:54PM -0500, Tom Lendacky wrote:
> On 8/10/21 1:45 PM, Kuppuswamy, Sathyanarayanan wrote:
> > 
> > 
> > On 7/27/21 3:26 PM, Tom Lendacky wrote:
> >> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> >> index de01903c3735..cafed6456d45 100644
> >> --- a/arch/x86/kernel/head64.c
> >> +++ b/arch/x86/kernel/head64.c
> >> @@ -19,7 +19,7 @@
> >>   #include <linux/start_kernel.h>
> >>   #include <linux/io.h>
> >>   #include <linux/memblock.h>
> >> -#include <linux/mem_encrypt.h>
> >> +#include <linux/protected_guest.h>
> >>   #include <linux/pgtable.h>
> >>     #include <asm/processor.h>
> >> @@ -285,7 +285,7 @@ unsigned long __head __startup_64(unsigned long
> >> physaddr,
> >>        * there is no need to zero it after changing the memory encryption
> >>        * attribute.
> >>        */
> >> -    if (mem_encrypt_active()) {
> >> +    if (prot_guest_has(PATTR_MEM_ENCRYPT)) {
> >>           vaddr = (unsigned long)__start_bss_decrypted;
> >>           vaddr_end = (unsigned long)__end_bss_decrypted;
> > 
> > 
> > Since this change is specific to AMD, can you replace PATTR_MEM_ENCRYPT with
> > prot_guest_has(PATTR_SME) || prot_guest_has(PATTR_SEV). It is not used in
> > TDX.
> 
> This is a direct replacement for now.

With current implementation of prot_guest_has() for TDX it breaks boot for
me.

Looking at code agains, now I *think* the reason is accessing a global
variable from __startup_64() inside TDX version of prot_guest_has().

__startup_64() is special. If you access any global variable you need to
use fixup_pointer(). See comment before __startup_64().

I'm not sure how you get away with accessing sme_me_mask directly from
there. Any clues? Maybe just a luck and complier generates code just right
for your case, I donno.

A separate point is that TDX version of prot_guest_has() relies on
cpu_feature_enabled() which is not ready at this point.

I think __bss_decrypted fixup has to be done if sme_me_mask is non-zero.
Or just do it uncoditionally because it's NOP for sme_me_mask == 0.

> I think the change you're requesting
> should be done as part of the TDX support patches so it's clear why it is
> being changed.
> 
> But, wouldn't TDX still need to do something with this shared/unencrypted
> area, though? Or since it is shared, there's actually nothing you need to
> do (the bss decrpyted section exists even if CONFIG_AMD_MEM_ENCRYPT is not
> configured)?

AFAICS, only kvmclock uses __bss_decrypted. We don't enable kvmclock in
TDX at the moment. It may change in the future.

-- 
 Kirill A. Shutemov

  parent reply	other threads:[~2021-08-11 12:19 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27 22:26 [PATCH 00/11] Implement generic prot_guest_has() helper function Tom Lendacky
2021-07-27 22:26 ` [PATCH 01/11] mm: Introduce a function to check for virtualization protection features Tom Lendacky
2021-07-28 13:17   ` Christoph Hellwig
2021-07-28 16:28     ` Borislav Petkov
2021-08-02 10:34   ` Joerg Roedel
2021-08-11 14:53   ` Kuppuswamy, Sathyanarayanan
2021-08-11 15:39     ` Tom Lendacky
2021-07-27 22:26 ` [PATCH 02/11] x86/sev: Add an x86 version of prot_guest_has() Tom Lendacky
2021-07-28 13:22   ` Christoph Hellwig
2021-07-29 14:24     ` Tom Lendacky
2021-08-02 10:35   ` Joerg Roedel
2021-07-27 22:26 ` [PATCH 03/11] powerpc/pseries/svm: Add a powerpc " Tom Lendacky
2021-07-27 22:26 ` [PATCH 04/11] x86/sme: Replace occurrences of sme_active() with prot_guest_has() Tom Lendacky
2021-08-02 10:37   ` Joerg Roedel
2021-07-27 22:26 ` [PATCH 05/11] x86/sev: Replace occurrences of sev_active() " Tom Lendacky
2021-08-02 10:42   ` Joerg Roedel
2021-07-27 22:26 ` [PATCH 06/11] x86/sev: Replace occurrences of sev_es_active() " Tom Lendacky
2021-08-02 10:45   ` Joerg Roedel
2021-08-09 21:59     ` Tom Lendacky
2021-08-09 22:08       ` Kuppuswamy, Sathyanarayanan
2021-07-27 22:26 ` [PATCH 07/11] treewide: Replace the use of mem_encrypt_active() " Tom Lendacky
2021-07-30 22:34   ` Sean Christopherson
2021-08-09 21:55     ` Tom Lendacky
2021-08-02 12:42   ` Christophe Leroy
2021-08-09 22:04     ` Tom Lendacky
2021-08-10 18:45   ` Kuppuswamy, Sathyanarayanan
2021-08-10 19:48     ` Tom Lendacky
2021-08-10 20:09       ` Kuppuswamy, Sathyanarayanan
2021-08-11 12:19       ` Kirill A. Shutemov [this message]
2021-08-11 15:52         ` Tom Lendacky
2021-08-12 10:07           ` Kirill A. Shutemov
2021-08-13 17:08             ` Tom Lendacky
2021-08-13 20:17               ` Tom Lendacky
2021-07-27 22:26 ` [PATCH 08/11] mm: Remove the now unused mem_encrypt_active() function Tom Lendacky
2021-08-02 10:47   ` Joerg Roedel
2021-07-27 22:26 ` [PATCH 09/11] x86/sev: " Tom Lendacky
2021-08-02 10:46   ` Joerg Roedel
2021-07-27 22:26 ` [PATCH 10/11] powerpc/pseries/svm: " Tom Lendacky
2021-07-27 22:26 ` [PATCH 11/11] s390/mm: " Tom Lendacky
2021-07-27 22:37 ` [PATCH 00/11] Implement generic prot_guest_has() helper function Tom Lendacky
2021-07-28 11:50 ` Christian König
2021-08-09  1:41 ` Kuppuswamy, Sathyanarayanan
2021-08-09 22:16   ` Tom Lendacky

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