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Re: [Xen-devel] [PATCH v2 06/27] x86/entry/64: Adapt assembly for PIE support
- To: Christopher Lameter <cl@xxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
- Date: Thu, 15 Mar 2018 11:18:19 +0100
- Cc: Kate Stewart <kstewart@xxxxxxxxxxxxxxxxxxx>, Nicolas Pitre <nicolas.pitre@xxxxxxxxxx>, Michal Hocko <mhocko@xxxxxxxx>, Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>, Petr Mladek <pmladek@xxxxxxxx>, Len Brown <len.brown@xxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Christopher Li <sparse@xxxxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, x86@xxxxxxxxxx, Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>, Pavel Machek <pavel@xxxxxx>, "H . Peter Anvin" <hpa@xxxxxxxxx>, kernel-hardening@xxxxxxxxxxxxxxxxxx, Jiri Slaby <jslaby@xxxxxxx>, Alok Kataria <akataria@xxxxxxxxxx>, linux-doc@xxxxxxxxxxxxxxx, linux-arch@xxxxxxxxxxxxxxx, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>, Baoquan He <bhe@xxxxxxxxxx>, Jonathan Corbet <corbet@xxxxxxx>, Joerg Roedel <joro@xxxxxxxxxx>, Radim Krčmář <rkrcmar@xxxxxxxxxx>, Kyle Huey <me@xxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-sparse@xxxxxxxxxxxxxxx, Matthias Kaehlcke <mka@xxxxxxxxxxxx>, Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>, Borislav Petkov <bp@xxxxxxx>, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, Alexey Dobriyan <adobriyan@xxxxxxxxx>, Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>, linux-crypto@xxxxxxxxxxxxxxx, kvm@xxxxxxxxxxxxxxx, Tom Lendacky <thomas.lendacky@xxxxxxx>, Rik van Riel <riel@xxxxxxxxxx>, "Jan H . Schönherr" <jschoenh@xxxxxxxxx>, Kees Cook <keescook@xxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, Dou Liyang <douly.fnst@xxxxxxxxxxxxxx>, Daniel Micay <danielmicay@xxxxxxxxx>, "H . J . Lu" <hjl.tools@xxxxxxxxx>, Steven Rostedt <rostedt@xxxxxxxxxxx>, Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>, Dennis Zhou <dennisszhou@xxxxxxxxx>, Jason Baron <jbaron@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Nicholas Piggin <npiggin@xxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxx>, Josh Poimboeuf <jpoimboe@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ashish Kalra <ashish@xxxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Kyle McMartin <kyle@xxxxxxxxxx>, "Paul E . McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>, linux-pm@xxxxxxxxxxxxxxx, Randy Dunlap <rdunlap@xxxxxxxxxxxxx>, "Rafael J . Wysocki" <rjw@xxxxxxxxxxxxx>, Cao jin <caoj.fnst@xxxxxxxxxxxxxx>, "David S . Miller" <davem@xxxxxxxxxxxxx>, Jia Zhang <qianyue.zj@xxxxxxxxxxxxxxx>, "Luis R . Rodriguez" <mcgrof@xxxxxxxxxx>, Lukas Wunner <lukas@xxxxxxxxx>, David Woodhouse <dwmw@xxxxxxxxxxxx>, Rob Landley <rob@xxxxxxxxxxx>, Philippe Ombredanne <pombredanne@xxxxxxxx>, Tejun Heo <tj@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Thomas Garnier <thgarnie@xxxxxxxxxx>, "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
- Delivery-date: Thu, 15 Mar 2018 10:18:48 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 14/03/2018 16:54, Christopher Lameter wrote:
>>> + pushq %rax /* Support Position Independent Code */
>>> + leaq 1f(%rip), %rax /* RIP */
>>> + xchgq %rax, (%rsp) /* Restore RAX, put 1f */
>>> iretq /* continues at repeat_nmi below */
>>> UNWIND_HINT_IRET_REGS
>>> 1:
>> Urgh, xchg with a memop has an implicit LOCK prefix.
> this_cpu_xchg uses no lock cmpxchg as a replacement to reduce latency.
That requires using a second register, since %rax is used as the
comparison source. At this point it's easier to just push %rax twice:
pushq %rax
pushq %rax
leaq 1f(%ip), %rax
movq %rax, 8(%rsp)
popq %rax
iretq
Paolo
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