[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3 4/9] Clear AC bit in RFLAGS to protect Xen itself by SMAP
> -----Original Message----- > From: Jan Beulich [mailto:JBeulich@xxxxxxxx] > Sent: Tuesday, April 29, 2014 3:21 PM > To: Wu, Feng > Cc: andrew.cooper3@xxxxxxxxxx; ian.campbell@xxxxxxxxxx; Dong, Eddie; > Nakajima, Jun; Tian, Kevin; xen-devel@xxxxxxxxxxxxx > Subject: RE: [PATCH v3 4/9] Clear AC bit in RFLAGS to protect Xen itself by > SMAP > > >>> On 29.04.14 at 05:06, <feng.wu@xxxxxxxxx> wrote: > > > > >> -----Original Message----- > >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx] > >> Sent: Monday, April 28, 2014 5:58 PM > >> To: Wu, Feng > >> Cc: andrew.cooper3@xxxxxxxxxx; ian.campbell@xxxxxxxxxx; Dong, Eddie; > >> Nakajima, Jun; Tian, Kevin; xen-devel@xxxxxxxxxxxxx > >> Subject: RE: [PATCH v3 4/9] Clear AC bit in RFLAGS to protect Xen itself by > > SMAP > >> > >> >>> On 28.04.14 at 11:43, <feng.wu@xxxxxxxxx> wrote: > >> > >> > > >> >> -----Original Message----- > >> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx] > >> >> Sent: Monday, April 28, 2014 5:26 PM > >> >> To: Wu, Feng > >> >> Cc: andrew.cooper3@xxxxxxxxxx; ian.campbell@xxxxxxxxxx; Dong, Eddie; > >> >> Nakajima, Jun; Tian, Kevin; xen-devel@xxxxxxxxxxxxx > >> >> Subject: Re: [PATCH v3 4/9] Clear AC bit in RFLAGS to protect Xen > >> >> itself by > >> > SMAP > >> >> > >> >> >>> On 28.04.14 at 05:15, <feng.wu@xxxxxxxxx> wrote: > >> >> > @@ -466,6 +468,7 @@ ENTRY(dom_crash_sync_extable) > >> >> > jmp asm_domain_crash_synchronous /* Does not > return */ > >> >> > > >> >> > ENTRY(common_interrupt) > >> >> > + ASM_CLAC > >> >> > SAVE_ALL > >> >> > movq %rsp,%rdi > >> >> > callq do_IRQ > >> >> > @@ -485,6 +488,7 @@ ENTRY(page_fault) > >> >> > movl $TRAP_page_fault,4(%rsp) > >> >> > /* No special register assumptions. */ > >> >> > GLOBAL(handle_exception) > >> >> > + ASM_CLAC > >> >> > SAVE_ALL > >> >> > >> >> Did you check whether the addition wouldn't better go right into > >> >> SAVE_ALL? > >> > > >> > Most of them can be moved into SAVE_ALL obviously, however, there are > two > >> > exceptions: > >> > > >> > 1. SAVE_ALL is not executed in the beginning of some exception handlers, > >> > such as, double_fault, nmi, etc. > >> > >> But that's orthogonal - I didn't say that would automatically cover > >> _all_ cases. > > > > So, do you think we can move CLAC into SAVE_ALL in these cases? Thanks! > > That was actually meant for you to figure out. But since you ask back, > yes, I don't see any case where it would be outright wrong, but there > are cases where it unnecessary, i.e. parameterizing SAVE_ALL might > nevertheless be desirable. Thanks for the suggestion. BTW, can we move SAVE_ALL into #ifdef __ASSEMBLY__ ...... #endif, since it is only used in assembly code? > > >> > 2. We don't need CLAC in .fixup section where SAVE_ALL is used. > >> > >> Do we not? > > > > I think the AC bit is clear when running SAVE_ALL in the .fixup section. > > Correct, but it would once again be harmless to do it here too. > > Jan Thanks, Feng _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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