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Shutemov" To: Tom Lendacky Subject: Re: [PATCH 07/11] treewide: Replace the use of mem_encrypt_active() with prot_guest_has() Message-ID: <20210812100724.t4cdh7xbkuqgnsc3@box.shutemov.name> References: <029791b24c6412f9427cfe6ec598156c64395964.1627424774.git.thomas.lendacky@amd.com> <166f30d8-9abb-02de-70d8-6e97f44f85df@linux.intel.com> <4b885c52-f70a-147e-86bd-c71a8f4ef564@amd.com> <20210811121917.ghxi7g4mctuybhbk@box.shutemov.name> <0a819549-e481-c004-7da8-82ba427b13ce@amd.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0a819549-e481-c004-7da8-82ba427b13ce@amd.com> Cc: linux-efi@vger.kernel.org, Brijesh Singh , kvm@vger.kernel.org, Peter Zijlstra , Dave Hansen , dri-devel@lists.freedesktop.org, platform-driver-x86@vger.kernel.org, Will Deacon , linux-s390@vger.kernel.org, Andi Kleen , x86@kernel.org, amd-gfx@lists.freedesktop.org, David Airlie , Ingo Molnar , linux-graphics-maintainer@vmware.com, Dave Young , Tianyu Lan , Thomas Zimmermann , Maarten Lankhorst , Maxime Ripard , Borislav Petkov , Andy Lutomirski , Thomas Gleixner , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Daniel Vetter , linux-fsdevel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Wed, Aug 11, 2021 at 10:52:55AM -0500, Tom Lendacky wrote: > On 8/11/21 7:19 AM, Kirill A. Shutemov wrote: > > 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 @@ > >>>> =A0 #include > >>>> =A0 #include > >>>> =A0 #include > >>>> -#include > >>>> +#include > >>>> =A0 #include > >>>> =A0 =A0 #include > >>>> @@ -285,7 +285,7 @@ unsigned long __head __startup_64(unsigned long > >>>> physaddr, > >>>> =A0=A0=A0=A0=A0=A0 * there is no need to zero it after changing the = memory encryption > >>>> =A0=A0=A0=A0=A0=A0 * attribute. > >>>> =A0=A0=A0=A0=A0=A0 */ > >>>> -=A0=A0=A0 if (mem_encrypt_active()) { > >>>> +=A0=A0=A0 if (prot_guest_has(PATTR_MEM_ENCRYPT)) { > >>>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 vaddr =3D (unsigned long)__start_bss_dec= rypted; > >>>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 vaddr_end =3D (unsigned long)__end_bss_d= ecrypted; > >>> > >>> > >>> Since this change is specific to AMD, can you replace PATTR_MEM_ENCRY= PT with > >>> prot_guest_has(PATTR_SME) || prot_guest_has(PATTR_SEV). It is not use= d 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 ri= ght > > for your case, I donno. > = > Hmm... yeah, could be that the compiler is using rip-relative addressing > for it because it lives in the .data section? I guess. It has to be fixed. It may break with complier upgrade or any random change around the code. BTW, does it work with clang for you? > For the static variables in mem_encrypt_identity.c I did an assembler rip > relative LEA, but probably could have passed physaddr to sme_enable() and > used a fixup_pointer() style function, instead. Sounds like a plan. > > A separate point is that TDX version of prot_guest_has() relies on > > cpu_feature_enabled() which is not ready at this point. > = > Does TDX have to do anything special to make memory able to be shared with > the hypervisor? Yes. But there's nothing that required any changes in early boot. It handled in ioremap/set_memory. > You might have to use something that is available earlier > than cpu_feature_enabled() in that case (should you eventually support > kvmclock). Maybe. > > 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 =3D=3D 0. > = > For SNP, we'll have to additionally call the HV to update the RMP to make > the memory shared. But that could also be done unconditionally since the > early_snp_set_memory_shared() routine will check for SNP before doing > anything. -- = Kirill A. Shutemov _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu