Liu Yu-B13201 wrote: > > > >> -----Original Message----- >> From: Alexander Graf [mailto:agraf@xxxxxxx] >> Sent: Friday, September 10, 2010 7:24 AM >> To: Liu Yu-B13201 >> Cc: kvm@xxxxxxxxxxxxxxx; kvm-ppc@xxxxxxxxxxxxxxx >> Subject: Re: [PATCH 2/2] kvm/e500v2: mapping guest TLB1 to host TLB0 >> >> >> On 08.09.2010, at 11:40, Liu Yu wrote: >> >> >>> Current guest TLB1 is mapped to host TLB1. >>> As host kernel only provides 4K uncontinuous pages, >>> we have to break guest large mapping into 4K shadow mappings. >>> These 4K shadow mappings are then mapped into host TLB1 on fly. >>> As host TLB1 only has 13 free entries, there's serious tlb miss. >>> >>> Since e500v2 has a big number of TLB0 entries, >>> it should be help to map those 4K shadow mappings to host TLB0. >>> To achieve this, we need to unlink guest tlb and host tlb, >>> So that guest TLB1 mappings can route to any host TLB0 >>> >> entries freely. >> >>> Pages/mappings are considerred in the same kind as host tlb entry. >>> This patch remove the link between pages and guest tlb >>> >> entry to do the unlink. >> >>> And keep host_tlb0_ref in each vcpu to trace pages. >>> Then it's easy to map guest TLB1 to host TLB0. >>> >>> In guest ramdisk boot test(guest mainly uses TLB1), >>> with this patch, the tlb miss number get down 90%. >>> >>> Signed-off-by: Liu Yu <yu.liu@xxxxxxxxxxxxx> >>> --- >>> arch/powerpc/include/asm/kvm_e500.h | 7 +- >>> arch/powerpc/kvm/e500.c | 4 + >>> arch/powerpc/kvm/e500_tlb.c | 280 >>> >> ++++++++++++----------------------- >> >>> arch/powerpc/kvm/e500_tlb.h | 1 + >>> 4 files changed, 104 insertions(+), 188 deletions(-) >>> >>> > > >>> -static unsigned int tlb1_entry_num; >>> +static inline unsigned int get_tlb0_entry_offset(u32 >>> >> eaddr, u32 esel) >> >>> +{ >>> + return ((eaddr & 0x7F000) >> (12 - host_tlb0_assoc_bit) | >>> + (esel & (host_tlb0_assoc - 1))); >>> +} >>> >>> void kvmppc_dump_tlbs(struct kvm_vcpu *vcpu) >>> { >>> @@ -62,11 +68,6 @@ static inline unsigned int tlb0_get_next_victim( >>> return victim; >>> } >>> >>> -static inline unsigned int tlb1_max_shadow_size(void) >>> -{ >>> - return tlb1_entry_num - tlbcam_index; >>> -} >>> - >>> static inline int tlbe_is_writable(struct tlbe *tlbe) >>> { >>> return tlbe->mas3 & (MAS3_SW|MAS3_UW); >>> @@ -100,7 +101,7 @@ static inline u32 >>> >> e500_shadow_mas2_attrib(u32 mas2, int usermode) >> >>> /* >>> * writing shadow tlb entry to host TLB >>> */ >>> -static inline void __write_host_tlbe(struct tlbe *stlbe) >>> +static inline void __host_tlbe_write(struct tlbe *stlbe) >>> { >>> mtspr(SPRN_MAS1, stlbe->mas1); >>> mtspr(SPRN_MAS2, stlbe->mas2); >>> @@ -109,25 +110,22 @@ static inline void >>> >> __write_host_tlbe(struct tlbe *stlbe) >> >>> __asm__ __volatile__ ("tlbwe\n" : : ); >>> } >>> >>> -static inline void write_host_tlbe(struct kvmppc_vcpu_e500 >>> >> *vcpu_e500, >> >>> - int tlbsel, int esel, struct tlbe *stlbe) >>> +static inline u32 host_tlb0_write(struct kvmppc_vcpu_e500 >>> >> *vcpu_e500, >> >>> + u32 gvaddr, struct tlbe *stlbe) >>> { >>> - local_irq_disable(); >>> - if (tlbsel == 0) { >>> - __write_host_tlbe(stlbe); >>> - } else { >>> - unsigned register mas0; >>> + unsigned register mas0; >>> >>> - mas0 = mfspr(SPRN_MAS0); >>> + local_irq_disable(); >>> >> Do you have to disable interrupts for a tlb write? If you get >> preempted before the write, the entry you overwrite could be >> different. But you don't protect against that either way. And >> if you get preempted afterwards, you could lose the entry. >> But since you enable interrupts beyond that, that could >> happen either way too. >> >> So what's the reason for the disable here? >> >> > > Hello Alex, > > Doesn't local_irq_disable() also disable preempt? > The reason to disable interrupts is because it's possible to have tlb > misses in interrupt service route. > Yes, local_irq_disable disables preempt. That's exactly what I was referring to :). I don't understand the statement about the service route. A tlb miss still arrives with local_irq_disable. Alex -- 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
