Hollis Blanchard wrote:
> On Sat, 2008-02-16 at 17:09 -0500, Marcelo Tosatti wrote:
>
>> plain text document attachment (kvm-multicall)
>> Batch pte updates and tlb flushes in lazy MMU mode.
>>
>> Signed-off-by: Marcelo Tosatti <[EMAIL PROTECTED]>
>> Cc: Anthony Liguori <[EMAIL PROTECTED]>
>>
>> Index: kvm.paravirt/arch/x86/kernel/kvm.c
>> ===================================================================
>> --- kvm.paravirt.orig/arch/x86/kernel/kvm.c
>> +++ kvm.paravirt/arch/x86/kernel/kvm.c
>> @@ -25,6 +25,74 @@
>> #include <linux/kvm_para.h>
>> #include <linux/cpu.h>
>> #include <linux/mm.h>
>> +#include <linux/hardirq.h>
>> +
>> +#define MAX_MULTICALL_NR (PAGE_SIZE / sizeof(struct kvm_multicall_entry))
>> +
>> +struct kvm_para_state {
>> + struct kvm_multicall_entry queue[MAX_MULTICALL_NR];
>> + int queue_index;
>> + enum paravirt_lazy_mode mode;
>> +};
>> +
>> +static DEFINE_PER_CPU(struct kvm_para_state, para_state);
>>
>
> AFAICS there is no guarantee about page-alignment here...
>
>
Right.
>> +static int kvm_hypercall_multicall(struct kvm_vcpu *vcpu, gpa_t addr, u32
>> nents)
>> +{
>> + int i, result = 0;
>> +
>> + ++vcpu->stat.multicall;
>> + vcpu->stat.multicall_nr += nents;
>> +
>> + for (i = 0; i < nents; i++) {
>> + struct kvm_multicall_entry mc;
>> + int ret;
>> +
>> + down_read(&vcpu->kvm->slots_lock);
>> + ret = kvm_read_guest(vcpu->kvm, addr, &mc, sizeof(mc));
>> + up_read(&vcpu->kvm->slots_lock);
>> + if (ret)
>> + return -KVM_EFAULT;
>> +
>> + ret = dispatch_hypercall(vcpu, mc.nr, mc.a0, mc.a1, mc.a2,
>> + mc.a3);
>> + if (ret)
>> + result = ret;
>> + addr += sizeof(mc);
>> + }
>> + if (result < 0)
>> + return -KVM_EINVAL;
>> + return result;
>> +}
>>
>
> ... but here you're assuming that 'queue' is physically contiguous,
> which is not necessarily true one you cross a page boundary.
>
Kernel data is physically contiguous (true for per-cpu data as well?),
so no there's issue here.
--
Do not meddle in the internals of kernels, for they are subtle and quick to
panic.
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