linux-kernel - Re: [PATCH 12/27] x86/pkru: Provide .*_pkru

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Message-ID: <20190411132418.GF30080@zn.tnic>
Date:   Thu, 11 Apr 2019 15:24:18 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Dave Hansen <dave.hansen@...el.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH 12/27] x86/pkru: Provide .*_pkru_ins() functions

On Wed, Apr 10, 2019 at 02:29:26PM -0700, Dave Hansen wrote:
> On 4/10/19 2:25 PM, Sebastian Andrzej Siewior wrote:
> >>  static inline void write_pkru(u32 pkru)
> >>  {
> >>  	if (boot_cpu_has(X86_FEATURE_OSPKE))
> >> -		__write_pkru(pkru);
> >> +		wrpkru(pkru);
> > I think if this is a simple
> > 
> >    's@...rite_pkru_ins@...kru@g'
> >    's@...ead_pkru_ins@...kru@g'
> > 
> > then it should work just fine and match what Dave asked for.
> 
> I'm fine with it either way, fwiw.

Final version:

---
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Date: Wed, 3 Apr 2019 18:41:41 +0200
Subject: [PATCH] x86/pkru: Provide *pkru() helpers
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Dave Hansen asked for __read_pkru() and __write_pkru() to be
symmetrical.

As part of the series __write_pkru() will read back the value and only
write it if it is different.

In order to make both functions symmetrical, move the function
containing only the opcode asm into a function called like the
instruction itself.

__write_pkru() will just invoke wrpkru() but in a follow-up patch will
also read back the value.

 [ bp: Convert asm opcode wrapper names to rd/wrpkru(). ]

Suggested-by: Dave Hansen <dave.hansen@...el.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Dave Hansen <dave.hansen@...el.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Joerg Roedel <jroedel@...e.de>
Cc: Juergen Gross <jgross@...e.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: kvm ML <kvm@...r.kernel.org>
Cc: Michal Hocko <mhocko@...e.cz>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: "Radim Krčmář" <rkrcmar@...hat.com>
Cc: Rik van Riel <riel@...riel.com>
Cc: x86-ml <x86@...nel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-13-bigeasy@linutronix.de
---
 arch/x86/include/asm/pgtable.h       |  2 +-
 arch/x86/include/asm/special_insns.h | 12 +++++++++---
 arch/x86/kvm/vmx/vmx.c               |  2 +-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 2779ace16d23..e8875ca75623 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -127,7 +127,7 @@ static inline int pte_dirty(pte_t pte)
 static inline u32 read_pkru(void)
 {
 	if (boot_cpu_has(X86_FEATURE_OSPKE))
-		return __read_pkru();
+		return rdpkru();
 	return 0;
 }
 
diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
index 43c029cdc3fe..34897e2b52c9 100644
--- a/arch/x86/include/asm/special_insns.h
+++ b/arch/x86/include/asm/special_insns.h
@@ -92,7 +92,7 @@ static inline void native_write_cr8(unsigned long val)
 #endif
 
 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
-static inline u32 __read_pkru(void)
+static inline u32 rdpkru(void)
 {
 	u32 ecx = 0;
 	u32 edx, pkru;
@@ -107,7 +107,7 @@ static inline u32 __read_pkru(void)
 	return pkru;
 }
 
-static inline void __write_pkru(u32 pkru)
+static inline void wrpkru(u32 pkru)
 {
 	u32 ecx = 0, edx = 0;
 
@@ -118,8 +118,14 @@ static inline void __write_pkru(u32 pkru)
 	asm volatile(".byte 0x0f,0x01,0xef\n\t"
 		     : : "a" (pkru), "c"(ecx), "d"(edx));
 }
+
+static inline void __write_pkru(u32 pkru)
+{
+	wrpkru(pkru);
+}
+
 #else
-static inline u32 __read_pkru(void)
+static inline u32 rdpkru(void)
 {
 	return 0;
 }
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index ab432a930ae8..dd1e1eea4f0b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6501,7 +6501,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
 	 */
 	if (static_cpu_has(X86_FEATURE_PKU) &&
 	    kvm_read_cr4_bits(vcpu, X86_CR4_PKE)) {
-		vcpu->arch.pkru = __read_pkru();
+		vcpu->arch.pkru = rdpkru();
 		if (vcpu->arch.pkru != vmx->host_pkru)
 			__write_pkru(vmx->host_pkru);
 	}
-- 
2.21.0


-- 
Regards/Gruss,
    Boris.

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