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Re: [PATCH v2 05/12] x86: rework arch_local_irq_restore() to not use popf
- To: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- From: Jürgen Groß <jgross@xxxxxxxx>
- Date: Fri, 20 Nov 2020 13:05:17 +0100
- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, luto@xxxxxxxxxx, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Deep Shah <sdeep@xxxxxxxxxx>, "VMware, Inc." <pv-drivers@xxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
- Delivery-date: Fri, 20 Nov 2020 12:05:27 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 20.11.20 12:59, Peter Zijlstra wrote:
On Fri, Nov 20, 2020 at 12:46:23PM +0100, Juergen Gross wrote:
+static __always_inline void arch_local_irq_restore(unsigned long flags)
+{
+ if (!arch_irqs_disabled_flags(flags))
+ arch_local_irq_enable();
+}
If someone were to write horrible code like:
local_irq_disable();
local_irq_save(flags);
local_irq_enable();
local_irq_restore(flags);
we'd be up some creek without a paddle... now I don't _think_ we have
genius code like that, but I'd feel saver if we can haz an assertion in
there somewhere...
Maybe something like:
#ifdef CONFIG_DEBUG_ENTRY // for lack of something saner
WARN_ON_ONCE((arch_local_save_flags() ^ flags) & X86_EFLAGS_IF);
#endif
At the end?
I'd be fine with that. I didn't add something like that because I
couldn't find a suitable CONFIG_ :-)
Juergen
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