RE: [Xen-ia64-devel][PATCH] vcpu_get_psr fix

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

Isaku Yamahata write on 2006年12月21日 17:41:
> On Thu, Dec 21, 2006 at 01:13:45PM +0800, Xu, Anthony wrote:
> 
> Could you elaborate?
> I don't see why it causes booting trouble and masking vpsr resolves
> it. 

Hi Isaku,

__kernel_syscall_via_epc will call fsys_bubble_down

Below code is used to form cr.ipsr
It wants to set ipsr.ri=1,

If (r29).ri=0 or 1, that's ok
But if (r29).ri=2, then ipsr.ri=3 issue happens


        /*
         * Reading psr.l gives us only bits 0-31, psr.it, and psr.mc.
         * The rest we have to synthesize.
         */
#       define PSR_ONE_BITS             ((3 << IA64_PSR_CPL0_BIT)       \
                                         | (0x1 << IA64_PSR_RI_BIT)     \
                                         | IA64_PSR_BN | IA64_PSR_I)

        movl r8=PSR_ONE_BITS                    // X
        ;;
        mov r25=ar.unat                         // M2 (5 cyc) save ar.unat
        mov r19=b6                              // I0   save b6 (2 cyc)
        mov r20=r1                              // A    save caller's gp in r20
        ;;
        or r29=r8,r29                           // A    construct cr.ipsr value 
to save
        mov b6=r18                              // I0   copy syscall 
entry-point to b6 (7 cyc)

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