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Date: Thu, 23 Sep 2021 11:32:27 -0500 From: Tom Lendacky <thomas.lendacky@....com> To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, x86@...nel.org, "H . Peter Anvin" <hpa@...or.com> Cc: Dave Hansen <dave.hansen@...el.com>, Tony Luck <tony.luck@...el.com>, Dan Williams <dan.j.williams@...el.com>, Andi Kleen <ak@...ux.intel.com>, Kirill Shutemov <kirill.shutemov@...ux.intel.com>, Sean Christopherson <seanjc@...gle.com>, Kuppuswamy Sathyanarayanan <knsathya@...nel.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH v6 05/10] x86/tdx: Handle port I/O On 9/22/21 5:52 PM, Kuppuswamy Sathyanarayanan wrote: > From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> > > TDX hypervisors cannot emulate instructions directly. This includes > port IO which is normally emulated in the hypervisor. All port IO > instructions inside TDX trigger the #VE exception in the guest and > would be normally emulated there. > > Also string I/O is not supported in TDX guest. So, unroll the string > I/O operation into a loop operating on one element at a time. This > method is similar to AMD SEV, so just extend the support for TDX guest > platform. > > Add a new confidential guest flag CC_ATTR_GUEST_UNROLL_STRING_IO to > add string unroll support in asm/io.h > > Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com> > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> > Reviewed-by: Andi Kleen <ak@...ux.intel.com> > Reviewed-by: Dan Williams <dan.j.williams@...el.com> > --- > > Changes since v5: > * Changed prot_guest_has() to cc_platform_has(). > > Changes since v4: > * Changed order of variable declaration in tdx_handle_io(). > * Changed tdg_* prefix with tdx_*. > > Changes since v3: > * Included PATTR_GUEST_UNROLL_STRING_IO protected guest flag > addition change in this patch. > * Rebased on top of Tom Lendacks protected guest change. > > Changes since v2: > * None > > Changes since v1: > * Fixed comments for tdg_handle_io(). > * Used _tdx_hypercall() instead of __tdx_hypercall() in tdg_handle_io(). > > arch/x86/include/asm/io.h | 7 +++++-- > arch/x86/kernel/cpu/intel.c | 1 + > arch/x86/kernel/tdx.c | 35 +++++++++++++++++++++++++++++++++++ > include/linux/cc_platform.h | 11 +++++++++++ > 4 files changed, 52 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h > index fa6aa43e5dc3..67e0c4a0a0f4 100644 > --- a/arch/x86/include/asm/io.h > +++ b/arch/x86/include/asm/io.h > @@ -40,6 +40,7 @@ > > #include <linux/string.h> > #include <linux/compiler.h> > +#include <linux/cc_platform.h> > #include <asm/page.h> > #include <asm/tdx.h> > #include <asm/early_ioremap.h> > @@ -310,7 +311,8 @@ static inline unsigned type in##bwl##_p(int port) \ > \ > static inline void outs##bwl(int port, const void *addr, unsigned long count) \ > { \ > - if (sev_key_active()) { \ > + if (sev_key_active() || \ > + cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO)) { \ Would it make sense to make sev_key_active() and sev_enable_key generic and just re-use those instead of adding CC_ATTR_GUEST_UNROLL_STRING_IO and having multiple conditions here? You can set the key in the TDX init routine just like SEV does. Thanks, Tom
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