Re: [Xen-ia64-devel] [PATCH 0/5] fix fpswa and related issues.

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Tue, Dec 09, 2008 at 06:29:41PM +0900, Isaku Yamahata wrote:
> 
> Hi. This patch series addresses the bug reported as
> http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1392
> Please test it.
> 
> It includes some clean ups and a reimplementation of fpswa hypercall.
> When fp fault/trap occurs, xen vmm tries to get a bundle in question
> from guest virtual address space. It sometimes fails because of
> I/D tlb cache. In that case inject the fault/trap into a guest
> and let a guest to call fpswa hypercall.
>     
> thanks        
> 
> _______________________________________________
> Xen-ia64-devel mailing list
> Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-ia64-devel
> 


I'd like to add one more patch.
It seems to take a while to address the case that fpswa
returns status > 0.
So keep the previous behavior in such cases for now.

IA64: make the fpswa emulation keep the previous behaviour.

When fpswa library return statue > 0, keep the previous behavior.
This case should be addressed somehow later, but it seems somewhat
difficult to resolve, so keep the previous behavor for now.

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>

diff --git a/xen/arch/ia64/xen/faults.c b/xen/arch/ia64/xen/faults.c
--- a/xen/arch/ia64/xen/faults.c
+++ b/xen/arch/ia64/xen/faults.c
@@ -319,11 +319,6 @@ handle_fpu_swa(int fp_fault, struct pt_r
        fpswa_ret_t ret;
        unsigned long rc;
 
-       unsigned long ipsr_save;
-       unsigned long fpsr_save;
-       unsigned long pr_save;
-       struct ia64_fpreg fp_save[6];
-
        fault_ip = regs->cr_iip;
        /*
         * When the FP trap occurs, the trapping instruction is completed.
@@ -342,28 +337,18 @@ handle_fpu_swa(int fp_fault, struct pt_r
                        rc = IA64_RETRY;
        }
        if (rc == IA64_RETRY) {
+               PSCBX(v, fpswa_ret) = (fpswa_ret_t){IA64_RETRY, 0, 0, 0};
                gdprintk(XENLOG_DEBUG,
                         "%s(%s): floating-point bundle at 0x%lx not mapped\n",
                         __FUNCTION__, fp_fault ? "fault" : "trap", fault_ip);
                return IA64_RETRY;
        }
 
-       /* If fpswa returns error, fp falut/trap is reflected and
-          a guest will call fpswa itself. So we have to revert the effect
-          to avoid calling fpswa twice. */
-       ipsr_save = regs->cr_ipsr;
-       fpsr_save = regs->ar_fpsr;
-       pr_save = regs->pr;
-       memcpy(fp_save, &regs->f6, sizeof(fp_save));
-
        ret = fp_emulate(fp_fault, &bundle, &regs->cr_ipsr, &regs->ar_fpsr,
                         &isr, &regs->pr, &regs->cr_ifs, regs);
 
        if (ret.status) {
-               regs->cr_ipsr = ipsr_save;
-               regs->ar_fpsr = fpsr_save;
-               regs->pr = pr_save;
-               memcpy(&regs->f6, fp_save, sizeof(fp_save));
+               PSCBX(v, fpswa_ret) = ret;
                printk("%s(%s): fp_emulate() returned %ld\n",
                       __FUNCTION__, fp_fault ? "fault" : "trap", ret.status);
        }
diff --git a/xen/arch/ia64/xen/hypercall.c b/xen/arch/ia64/xen/hypercall.c
--- a/xen/arch/ia64/xen/hypercall.c
+++ b/xen/arch/ia64/xen/hypercall.c
@@ -164,6 +164,13 @@ fw_hypercall_fpswa (struct vcpu *v, stru
        struct page_info *hp_page = NULL;
        struct page_info *hv_page = NULL;
        XEN_EFI_RR_DECLARE(rr6, rr7);
+
+       if (unlikely(PSCBX(v, fpswa_ret).status != 0 && 
+                    PSCBX(v, fpswa_ret).status != IA64_RETRY)) {
+               ret = PSCBX(v, fpswa_ret);
+               PSCBX(v, fpswa_ret) = (fpswa_ret_t){0, 0, 0, 0};
+               return ret;
+       }
 
        if (!fpswa_interface)
                goto error;
diff --git a/xen/include/asm-ia64/domain.h b/xen/include/asm-ia64/domain.h
--- a/xen/include/asm-ia64/domain.h
+++ b/xen/include/asm-ia64/domain.h
@@ -288,6 +288,7 @@ struct arch_vcpu {
     char irq_new_condition;    // vpsr.i/vtpr change, check for pending VHPI
     char hypercall_continuation;
 
+    fpswa_ret_t fpswa_ret;     /* save return values of FPSWA emulation */
     struct timer hlt_timer;
     struct arch_vmx_struct arch_vmx; /* Virtual Machine Extensions */
 

-- 
yamahata

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