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Date:   Tue, 13 Mar 2018 15:49:56 +0300
From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     Kai Huang <kai.huang@linux.intel.com>
Cc:     dave.hansen@intel.com, peterz@infradead.org, hpa@zytor.com,
        mingo@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de,
        torvalds@linux-foundation.org, kirill.shutemov@linux.intel.com,
        thomas.lendacky@amd.com, linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/mm] x86/tme: Detect if TME and MKTME is activated by
 BIOS
Message-ID: <20180313124956.z426zmsr4xl6zomx@node.shutemov.name>
References: <20180305162610.37510-3-kirill.shutemov@linux.intel.com>
 <tip-cb06d8e3d020c30fe10ae711c925a5319ab82c88@git.kernel.org>
 <1520907122.6421.8.camel@linux.intel.com>
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On Tue, Mar 13, 2018 at 03:12:02PM +1300, Kai Huang wrote:
> It seems setup_pku() will call get_cpu_cap to restore c->x86_phys_bits
> later? In which case I think you need to change setup_pku as well.

Thanks for catching this.

I think setup_pku() shouldn't call get_cpu_cap().

Any objections against this:

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 348cf4821240..ce10d8ae4cd6 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -362,6 +362,8 @@ static bool pku_disabled;

 static __always_inline void setup_pku(struct cpuinfo_x86 *c)
 {
+       u32 eax, ebx, ecx, edx;
+
        /* check the boot processor, plus compile options for PKU: */
        if (!cpu_feature_enabled(X86_FEATURE_PKU))
                return;
@@ -377,7 +379,8 @@ static __always_inline void setup_pku(struct cpuinfo_x86 *c)
         * cpuid bit to be set.  We need to ensure that we
         * update that bit in this CPU's "cpu_info".
         */
-       get_cpu_cap(c);
+       cpuid_count(0x00000007, 0, &eax, &ebx, &ecx, &edx);
+       c->x86_capability[CPUID_7_ECX] = ecx;
 }

 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS

> And for the comments here, I think it can be refined. It is true that
> VM guest needs to know bits of physical address, but this info is not
> used only by VM. I think the reason we need to update is this is simply
> the fact.

Fair enough. Like this?

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index e8ddc6dcfd53..ac45ba7398d9 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -612,11 +612,8 @@ static void detect_tme(struct cpuinfo_x86 *c)
 #endif

        /*
-        * Exclude KeyID bits from physical address bits.
-        *
-        * We have to do this even if we are not going to use KeyID bits
-        * ourself. VM guests still have to know that these bits are not usable
-        * for physical address.
+        * KeyID bits effectively lower number of physical address bits.
+        * Let's update cpuinfo_x86::x86_phys_bits to reflect the fact.
         */
        c->x86_phys_bits -= keyid_bits;
 }
-- 
 Kirill A. Shutemov