Re: [Xen-devel] [PATCH v2 2/2] x86/vm_event: Allow overwriting Xen's i-cache used for emulation

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 09/15/16 19:51, Tamas K Lengyel wrote:
> When emulating instructions Xen's emulator maintains a small i-cache fetched
> from the guest memory. This patch extends the vm_event interface to allow
> overwriting this i-cache via a buffer returned in the vm_event response.
> 
> When responding to a SOFTWARE_BREAKPOINT event (INT3) the monitor subscriber
> normally has to remove the INT3 from memory - singlestep - place back INT3
> to allow the guest to continue execution. This routine however is susceptible
> to a race-condition on multi-vCPU guests. By allowing the subscriber to return
> the i-cache to be used for emulation it can side-step the problem by returning
> a clean buffer without the INT3 present.
> 
> As part of this patch we rename hvm_mem_access_emulate_one to
> hvm_emulate_one_vm_event to better reflect that it is used in various vm_event
> scenarios now, not just in response to mem_access events.
> 
> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
> ---
> Cc: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: Jun Nakajima <jun.nakajima@xxxxxxxxx>
> Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
> Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> Cc: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Julien Grall <julien.grall@xxxxxxx>
> 
> v2: rework hvm_mem_access_emulate_one switch statement
>     add BUILD_BUG_ON to ensure internal and vm_event buffer sizes match
> 
> Note: this patch has now been fully tested and works as intended

Acked-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>

On a side note, I see that you're using an email address that's
different from the one in MAINTAINERS. Should we update the MAINTAINERS
file?


Thanks,
Razvan

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