From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: [Patch 1/3 v2] x86/irq: local_irq_restore() should not blindly popf Date: Mon, 21 Oct 2013 19:18:19 +0100 Message-ID: References: <1382373216-31496-1-git-send-email-andrew.cooper3@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1382373216-31496-1-git-send-email-andrew.cooper3@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andrew Cooper , Xen-devel Cc: Jan Beulich List-Id: xen-devel@lists.xenproject.org On 21/10/2013 17:33, "Andrew Cooper" wrote: > local_irq_restore() should only be concerned with possibly changing the > interrupt flag. A blind popf could corrupt other system flags. > > While playing in this area, fixup an opencoded use of X86_EFLAGS_IF. > > Signed-off-by: Andrew Cooper > CC: Keir Fraser > CC: Jan Beulich > > --- > > This is rather more RFC. It boots and runs VMs, so I am fairly sure it is > functionally correct, but I cant help feeling there might be a neater way to > do the inline assembly. Suggestions welcome. > --- > xen/include/asm-x86/system.h | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/xen/include/asm-x86/system.h b/xen/include/asm-x86/system.h > index 6ab7d56..ff52671 100644 > --- a/xen/include/asm-x86/system.h > +++ b/xen/include/asm-x86/system.h > @@ -3,6 +3,7 @@ > > #include > #include > +#include > > #define read_segment_register(name) \ > ({ u16 __sel; \ > @@ -159,15 +160,19 @@ static always_inline unsigned long __cmpxchg( > #define local_irq_restore(x) \ > ({ \ > BUILD_BUG_ON(sizeof(x) != sizeof(long)); \ > - asm volatile ( "push" __OS " %0 ; popf" __OS \ > - : : "g" (x) : "memory", "cc" ); \ > + asm volatile ( \ > + "pushf" __OS "\n\t" \ > + "and" __OS " %0, (%%" __OP "sp)\n\t" \ > + "orw %1, (%%" __OP "sp)\n\t" \ > + "popf" __OS "\n\t" : : "g" ( ~X86_EFLAGS_IF ), \ Would this be better as a constant constraint ("i")? > + "g" ( x & X86_EFLAGS_IF ) ); \ > }) > > static inline int local_irq_is_enabled(void) > { > unsigned long flags; > local_save_flags(flags); > - return !!(flags & (1<<9)); /* EFLAGS_IF */ > + return !!(flags & X86_EFLAGS_IF); > } > > #define BROKEN_ACPI_Sx 0x0001