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Subject: Re: [PATCH RFC 5/6] KVM: mark requests that do not need a wakeup
To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
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References: <20170406202056.18379-1-rkrcmar@redhat.com>
 <20170406202056.18379-6-rkrcmar@redhat.com>
Cc: Christoffer Dall <cdall@linaro.org>, Andrew Jones <drjones@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Cornelia Huck <cornelia.huck@de.ibm.com>,
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        Paul Mackerras <paulus@ozlabs.org>
From: Marc Zyngier <marc.zyngier@arm.com>
Organization: ARM Ltd
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Date: Fri, 7 Apr 2017 09:27:00 +0100
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On 06/04/17 21:20, Radim Krčmář wrote:
> Some operations must ensure that the guest is not running with stale
> data, but if the guest is halted, then the update can wait until another
> event happens.  kvm_make_all_requests() currently doesn't wake up, so we
> can mark all requests used with it.
> 
> First 8 bits were arbitrarily reserved for request numbers.
> 
> Most uses of requests have the request type as a constant, so a compiler
> will optimize the '&'.
> 
> An alternative would be to have an inline function that would return
> whether the request needs a wake-up or not, but I like this one better
> even though it might produce worse assembly.
> 
> Suggested-by: Christoffer Dall <cdall@linaro.org>
> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
> ---
>   Btw. do you recall which macro allowed to define bitmasks?  (It has
>   two arguments, FROM and TO.)

GENMASK (and its _ULL variant), defined in include/linux/bitops.h.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...