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Date: Thu, 23 Sep 2021 10:24:20 -0700 From: "Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@...ux.intel.com> To: Tom Lendacky <thomas.lendacky@....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 9/23/21 9:32 AM, Tom Lendacky wrote: > 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. Any reason for using sev_enable_key over CC attribute? IMO, CC attribute exist to generalize the common feature code. My impression is SEV is specific to AMD code. > > Thanks, > Tom > -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
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