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Re: [Qemu-devel] [PATCH v3 2/2] Xen: Use the ioreq-server API when avail
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v3 2/2] Xen: Use the ioreq-server API when available |
Date: |
Thu, 16 Oct 2014 09:37:14 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.1 |
Il 15/10/2014 19:30, Peter Maydell ha scritto:
> On 15 October 2014 11:16, Paul Durrant <address@hidden> wrote:
>> The ioreq-server API added to Xen 4.5 offers better security than
>> the existing Xen/QEMU interface because the shared pages that are
>> used to pass emulation request/results back and forth are removed
>> from the guest's memory space before any requests are serviced.
>> This prevents the guest from mapping these pages (they are in a
>> well known location) and attempting to attack QEMU by synthesizing
>> its own request structures. Hence, this patch modifies configure
>> to detect whether the API is available, and adds the necessary
>> code to use the API if it is.
>
> This commit message doesn't mention it, but presumably this is
> all x86-specific given it's in a file which is only used for
> x86 Xen?
>
>> +static void xen_hvm_pre_save(void *opaque)
>> +{
>> + XenIOState *state = opaque;
>> +
>> + /* Stop servicing emulation requests */
>> + xen_set_ioreq_server_state(xen_xc, xen_domid, state->ioservid, 0);
>> + xen_destroy_ioreq_server(xen_xc, xen_domid, state->ioservid);
>> +}
>> +
>> +static const VMStateDescription vmstate_xen_hvm = {
>> + .name = "xen-hvm",
>> + .version_id = 4,
>> + .minimum_version_id = 4,
>
> This is new in upstream so why's it starting at version 4?
>
>> + .pre_save = xen_hvm_pre_save,
>> + .fields = (VMStateField[]) {
>> + VMSTATE_END_OF_LIST()
>> + },
>
> A vmstate which doesn't actually save any state? This seems
> rather suspicious...
>
>> @@ -1060,12 +1185,19 @@ int xen_hvm_init(ram_addr_t *below_4g_mem_size,
>> ram_addr_t *above_4g_mem_size,
>> xen_ram_init(below_4g_mem_size, above_4g_mem_size, ram_size,
>> ram_memory);
>>
>> qemu_add_vm_change_state_handler(xen_hvm_change_state_handler, state);
>> + vmstate_register(NULL, 0, &vmstate_xen_hvm, state);
>
> Is the new use of vmstate_register() really necessary?
> Usually the state you're saving corresponds to some QOM
> device whose vmsd field you can use instead.
In this case, it seems like a job for a vmstate change handler.
Paolo
- Re: [Qemu-devel] [PATCH v3 1/2] Add device listener interface, (continued)
[Qemu-devel] [PATCH v3 2/2] Xen: Use the ioreq-server API when available, Paul Durrant, 2014/10/15
Re: [Qemu-devel] [PATCH v3 2/2] Xen: Use the ioreq-server API when available, Paul Durrant, 2014/10/16
Re: [Qemu-devel] [PATCH v3 2/2] Xen: Use the ioreq-server API when available, Stefano Stabellini, 2014/10/16
Re: [Qemu-devel] [PATCH v3 2/2] Xen: Use the ioreq-server API when available, Peter Maydell, 2014/10/15
Re: [Qemu-devel] [PATCH v3 2/2] Xen: Use the ioreq-server API when available, Paul Durrant, 2014/10/16
Re: [Qemu-devel] [PATCH v3 2/2] Xen: Use the ioreq-server API when available, Paul Durrant, 2014/10/16
Re: [Qemu-devel] [PATCH v3 2/2] Xen: Use the ioreq-server API when available, Stefano Stabellini, 2014/10/16
Re: [Qemu-devel] [PATCH v3 2/2] Xen: Use the ioreq-server API when available, Peter Maydell, 2014/10/16
Re: [Qemu-devel] [PATCH v3 2/2] Xen: Use the ioreq-server API when available, Stefano Stabellini, 2014/10/16