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Re: Magic Page in e500v2

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Hi Aashish,

On 05/21/2012 01:51 PM, Aashish Mittal wrote:
Hi
I'm working on KVM optimizations on Powerpc e500v2 embedded architecture. For my
project i'm trying to increase the size of shared region mapped my Magic Page
between host and guest for paravirtual support. I was expecting this would
possible since we are using a TLB1 entry to map the magic page entry inside the
host. I'm trying to increase it's size to 1MB. I've declared a shared structure
tcache of 1MB similar to vcpu->arch.shared and trying to map it in the guest
virtual space. The shared page earlier is now the last page of this tcache
structure.

This is the modified code :

Initialization in e500.c in function kvmppc_core_vcpu_create

         shared = (void*)__get_free_pages(GFP_KERNEL|__GFP_ZERO,10);
         vcpu->arch.tcache = (void*)(shared);
         vcpu->arch.shared = (void*)(shared + (((1<<  10)-1)<<PAGE_SHIFT));

Did you also change the shared page elements to still be within the first page? Otherwise the offset wouldn't fit into the immediate fields of the asm instructions. We can't reach as low as -1MB with all operations.


Alex

	

void kvmppc_map_magic(struct kvm_vcpu *vcpu)
{
	struct kvmppc_vcpu_e500 *vcpu_e500 = to_e500(vcpu);
	struct kvm_book3e_206_tlb_entry magic;
	ulong shared_page = ((ulong)vcpu->arch.tcache)&  PAGE_MASK;
	ulong page = shared_page;
	unsigned int stid;
	pfn_t pfn,pfn1;
         int i = 0;

         for(i=0;i<  1024;i++){
           pfn1 = (pfn_t)virt_to_phys((void *)page)>>  PAGE_SHIFT;
	  get_page(pfn_to_page(pfn1));
           page +=  0x1000;
	}
	
         pfn = (pfn_t)virt_to_phys((void *)shared_page)>>  PAGE_SHIFT;


	preempt_disable();
	stid = e500_get_sid(vcpu_e500, 0, 0, 0, 0);

	magic.mas1 = MAS1_VALID | MAS1_TS | MAS1_TID(stid) |
		     MAS1_TSIZE(BOOK3E_PAGESZ_1M);
	magic.mas2 = (vcpu->arch.magic_page_ea&  0xfff00000)| MAS2_M;

	magic.mas7_3 = ((u64)pfn<<  PAGE_SHIFT) |
		       MAS3_SW | MAS3_SR | MAS3_UW | MAS3_UR;

	__write_host_tlbe(&magic, MAS0_TLBSEL(1) | MAS0_ESEL(tlbcam_index));
	preempt_enable();
}

But i'm experiencing the following error printed in the guest

KVM: Live patching for a fast VM worked
initcall kvm_guest_init+0x0/0x1f8 returned with disabled interrupts
initcall migration_init+0x0/0x8c returned with disabled interrupts

and then the guest just hangs.

Does anybody have any idea how to map it correctly

Thanks


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