On 20.03.2013, at 18:45, Bharat Bhushan wrote: > EPCR.DUVD controls whether the debug events can come in > hypervisor mode or not. When KVM guest is using the debug > resource then we do not want debug events to be captured > in guest entry/exit path. So we set EPCR.DUVD when entering > and clears EPCR.DUVD when exiting from guest. > > Debug instruction complete is a post-completion debug > exception but debug event gets posted on the basis of MSR > before the instruction is executed. Now if the instruction > switches the context from guest mode (MSR.GS = 1) to hypervisor > mode (MSR.GS = 0) then the xSRR0 points to first instruction of > KVM handler and xSRR1 points that MSR.GS is clear > (hypervisor context). Now as xSRR1.GS is used to decide whether > KVM handler will be invoked to handle the exception or host > host kernel debug handler will be invoked to handle the exception. > This leads to host kernel debug handler handling the exception > which should either be handled by KVM. > > This is tested on e500mc in 32 bit mode > > Signed-off-by: Bharat Bhushan <bharat.bhushan@xxxxxxxxxxxxx> > --- > v0: > - Do not apply this change for debug_crit as we do not know those chips have issue or not. > - corrected 64bit case branching > > arch/powerpc/kernel/exceptions-64e.S | 29 ++++++++++++++++++++++++++++- > arch/powerpc/kernel/head_booke.h | 26 ++++++++++++++++++++++++++ > 2 files changed, 54 insertions(+), 1 deletions(-) > > diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S > index 4684e33..8b26294 100644 > --- a/arch/powerpc/kernel/exceptions-64e.S > +++ b/arch/powerpc/kernel/exceptions-64e.S > @@ -516,6 +516,33 @@ kernel_dbg_exc: > andis. r15,r14,DBSR_IC@h > beq+ 1f > > +#ifdef CONFIG_KVM_BOOKE_HV > + /* > + * EPCR.DUVD controls whether the debug events can come in > + * hypervisor mode or not. When KVM guest is using the debug > + * resource then we do not want debug events to be captured > + * in guest entry/exit path. So we set EPCR.DUVD when entering > + * and clears EPCR.DUVD when exiting from guest. > + * Debug instruction complete is a post-completion debug > + * exception but debug event gets posted on the basis of MSR > + * before the instruction is executed. Now if the instruction > + * switches the context from guest mode (MSR.GS = 1) to hypervisor > + * mode (MSR.GS = 0) then the xSRR0 points to first instruction of Can't we just execute that code path with MSR.DE=0? Alex > + * KVM handler and xSRR1 points that MSR.GS is clear > + * (hypervisor context). Now as xSRR1.GS is used to decide whether > + * KVM handler will be invoked to handle the exception or host > + * host kernel debug handler will be invoked to handle the exception. > + * This leads to host kernel debug handler handling the exception > + * which should either be handled by KVM. > + */ > + mfspr r10, SPRN_EPCR > + andis. r10,r10,SPRN_EPCR_DUVD@h > + beq+ 2f > + > + andis. r10,r9,MSR_GS@h > + beq+ 3f > +2: > +#endif > LOAD_REG_IMMEDIATE(r14,interrupt_base_book3e) > LOAD_REG_IMMEDIATE(r15,interrupt_end_book3e) > cmpld cr0,r10,r14 > @@ -523,7 +550,7 @@ kernel_dbg_exc: > blt+ cr0,1f > bge+ cr1,1f > > - /* here it looks like we got an inappropriate debug exception. */ > +3: /* here it looks like we got an inappropriate debug exception. */ > lis r14,DBSR_IC@h /* clear the IC event */ > rlwinm r11,r11,0,~MSR_DE /* clear DE in the DSRR1 value */ > mtspr SPRN_DBSR,r14 > diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h > index 5f051ee..edc6a3b 100644 > --- a/arch/powerpc/kernel/head_booke.h > +++ b/arch/powerpc/kernel/head_booke.h > @@ -285,7 +285,33 @@ label: > mfspr r10,SPRN_DBSR; /* check single-step/branch taken */ \ > andis. r10,r10,(DBSR_IC|DBSR_BT)@h; \ > beq+ 2f; \ > +#ifdef CONFIG_KVM_BOOKE_HV \ > + /* \ > + * EPCR.DUVD controls whether the debug events can come in \ > + * hypervisor mode or not. When KVM guest is using the debug \ > + * resource then we do not want debug events to be captured \ > + * in guest entry/exit path. So we set EPCR.DUVD when entering \ > + * and clears EPCR.DUVD when exiting from guest. \ > + * Debug instruction complete is a post-completion debug \ > + * exception but debug event gets posted on the basis of MSR \ > + * before the instruction is executed. Now if the instruction \ > + * switches the context from guest mode (MSR.GS = 1) to hypervisor \ > + * mode (MSR.GS = 0) then the xSRR0 points to first instruction of \ > + * KVM handler and xSRR1 points that MSR.GS is clear \ > + * (hypervisor context). Now as xSRR1.GS is used to decide whether \ > + * KVM handler will be invoked to handle the exception or host \ > + * host kernel debug handler will be invoked to handle the exception. \ > + * This leads to host kernel debug handler handling the exception \ > + * which should either be handled by KVM. \ > + */ \ > + mfspr r10, SPRN_EPCR; \ > + andis. r10,r10,SPRN_EPCR_DUVD@h; \ > + beq+ 3f; \ > \ > + andis. r10,r9,MSR_GS@h; \ > + beq+ 1f; \ > +3: \ > +#endif \ > lis r10,KERNELBASE@h; /* check if exception in vectors */ \ > ori r10,r10,KERNELBASE@l; \ > cmplw r12,r10; \ > -- > 1.7.0.4 > > > -- > To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
