linux-kernel - Re: [RFC v2-fix-v3 1/1] x86/tdx: Skip WBINVD instruction for TDX guest

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Date:   Tue, 8 Jun 2021 17:14:27 -0700
From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Raj Ashok <ashok.raj@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>
Subject: Re: [RFC v2-fix-v3 1/1] x86/tdx: Skip WBINVD instruction for TDX
 guest



On 6/8/21 5:07 PM, Dan Williams wrote:
> That works too, but I assume if ACPI_FLUSH_CPU_CACHE() itself is going
> to be changed rather than sprinkling protected_guest_has() checks in a
> few places it will need to assert why changing all of those at once is
> correct. Otherwise I expect Rafael to ask why this global change of
> the ACPI_FLUSH_CPU_CACHE() policy is ok.

Yes. I am fixing it as below.

--- a/arch/x86/include/asm/acenv.h
+++ b/arch/x86/include/asm/acenv.h
@@ -10,10 +10,15 @@
  #define _ASM_X86_ACENV_H

  #include <asm/special_insns.h>
+#include <asm/protected_guest.h>

  /* Asm macros */

-#define ACPI_FLUSH_CPU_CACHE() wbinvd()
+#define ACPI_FLUSH_CPU_CACHE()                         \
+do {                                                   \
+       if (!prot_guest_has(PR_GUEST_DISABLE_WBINVD))   \
+               wbinvd();                               \
+} while (0)


-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer