Hi,
You are right. The ar registers should not be destroyed.
So, I will try to make a patch which fixes it.
Thanks,
KAZ
From: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
Subject: mca handler
Date: Thu, 17 Jul 2008 11:54:46 +0900
> Hi.
> While I was debugging kexec/kdump, I have a question about the mca
> handler. I cited the related hunks below. Could you please clarify them?
>
> On mca the firmware saves non-banked and banked general registers
> and the most of ar registers must be unchanged.
> However before ia64_os_mca_proc_state_dump saves such registers,
> the cited hunks unconditionally overwrite ar.k[36] so that
> they are destroyed. Am I missing anything?
>
>
> changeset: 12447:2afdc0066df6
> user: awilliam@xxxxxxxxxxx
> date: Sun Oct 29 09:27:11 2006 -0700
> files: xen/arch/ia64/linux-xen/mca_asm.S
> description:
> [IA64] MCA support - Add percpu data physical addr mca_asm.S
>
> Signed-off-by: Yutaka Ezaki <yutaka.ezaki@xxxxxxxxxxxxxx>
> Signed-off-by: Masaki Kanno <kanno.masaki@xxxxxxxxxxxxxx>
> Signed-off-by: Kazuhiro Suzuki <kaz@xxxxxxxxxxxxxx>
> ...
> ...
> @@ -132,7 +153,40 @@
> .text
> .align 16
>
> -#ifndef XEN
> +#ifdef XEN
> +/*
> + * void set_per_cpu_data(void)
> + * {
> + * int i;
> + * for (i = 0; i < 64; i++) {
> + * if (ia64_mca_tlb_list[i].cr_lid == ia64_getreg(_IA64_REG_CR_LID)) {
> + * ia64_set_kr(IA64_KR_PER_CPU_DATA,
> ia64_mca_tlb_list[i].percpu_paddr);
> + * return;
> + * }
> + * }
> + * while(1); // Endless loop on error
> + * }
> + */
> +#define SET_PER_CPU_DATA() \
> + LOAD_PHYSICAL(p0,r2,ia64_mca_tlb_list);; \
> + mov r7 = r0; \
> + mov r6 = r0;; \
> + adds r3 = IA64_MCA_PERCPU_OFFSET, r2; \
> +1: add r4 = r6, r2; \
> + mov r5=cr.lid;; \
> + adds r7 = 1, r7; \
> + ld8 r4 = [r4];; \
> + cmp.ne p6, p7 = r5, r4; \
> + cmp4.lt p8, p9 = NR_CPUS-1, r7; \
> +(p7) br.cond.dpnt 3f; \
> + adds r6 = 16, r6; \
> +(p9) br.cond.sptk 1b; \
> +2: br 2b;; /* Endless loop on error */ \
> +3: add r4 = r6, r3;; \
> + ld8 r4 = [r4];; \
> + mov ar.k3=r4
> +#endif /* XEN */
> +
> ...
> @@ -235,6 +327,9 @@
> cmp.ne p6,p0=r4,r0
> (p6) br ia64_os_mca_spin
>
> +#ifdef XEN
> + SET_PER_CPU_DATA();;
> +#endif
> // Save the SAL to OS MCA handoff state as defined
> // by SAL SPEC 3.0
> // NOTE : The order in which the state gets saved
> @@ -250,7 +345,19 @@
>
> ia64_os_mca_done_dump:
>
> +#ifdef XEN
> + // Set current to ar.k6
> + GET_THIS_PADDR(r2,cpu_kr);;
> + add r2=IA64_KR_CURRENT_OFFSET,r2;;
> + ld8 r2=[r2];;
> + mov ar.k6=r2;;
> +
> + GET_THIS_PADDR(r2,ia64_sal_to_os_handoff_state_addr);;
> + ld8 r2=[r2];;
> + adds r16=56,r2
> +#else
> LOAD_PHYSICAL(p0,r16,ia64_sal_to_os_handoff_state+56)
> +#endif
> ;;
> ld8 r18=[r16] // Get processor state parameter on existing
> PA
> LE_CHECK.
> ;;
> ...
> @@ -874,12 +1003,6 @@
> br ia64_os_mca_done_restore;;
>
>
> //EndStub/////////////////////////////////////////////////////////////////////
> /
> -#else
> -ia64_os_mca_dispatch:
> -1:
> - br.sptk 1b
> -ia64_os_mca_dispatch_end:
> -#endif /* !XEN */
>
>
> // ok, the issue here is that we need to save state information so
> @@ -911,6 +1034,15 @@
>
> GLOBAL_ENTRY(ia64_monarch_init_handler)
> .prologue
> +#ifdef XEN /* Need in ia64_monarch_init_handler? */
> + SET_PER_CPU_DATA();;
> +
> + // Set current to ar.k6
> + GET_THIS_PADDR(r2,cpu_kr);;
> + add r2=IA64_KR_CURRENT_OFFSET,r2;;
> + ld8 r2=[r2];;
> + mov ar.k6=r2;;
> +#endif
> // stash the information the SAL passed to os
> SAL_TO_OS_MCA_HANDOFF_STATE_SAVE(r2)
> ;;
>
>
>
> --
> yamahata
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