linux-kernel - Re: [PATCH v4 07/10] KVM: selftests: Support multiple vCPUs in demand paging test

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Message-ID: <df86f0da-366d-bb20-d1d0-125697c660a8@redhat.com>
Date:   Sat, 25 Jan 2020 10:39:20 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Andrew Jones <drjones@...hat.com>, Ben Gardon <bgardon@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Cannon Matthews <cannonmatthews@...gle.com>,
        Peter Xu <peterx@...hat.com>, Peter Shier <pshier@...gle.com>,
        Oliver Upton <oupton@...gle.com>
Subject: Re: [PATCH v4 07/10] KVM: selftests: Support multiple vCPUs in demand
 paging test

On 24/01/20 11:49, Andrew Jones wrote:
>> +
>> +	/*
>> +	 * Reserve twice the ammount of memory needed to map the test region and
>> +	 * the page table / stacks region, at 4k, for page tables. Do the
>> +	 * calculation with 4K page size: the smallest of all archs. (e.g., 64K
>> +	 * page size guest will need even less memory for page tables).
>> +	 */
>> +	pages += (2 * pages) / PTES_PER_4K_PT;
>> +	pages += ((2 * vcpus * vcpu_memory_bytes) >> PAGE_SHIFT_4K) /
>> +		 PTES_PER_4K_PT;
> pages needs to be rounded up to the next multiple of 16 in order for this
> to work on aarch64 machines with 64k pages.

I think this is best done with a generic function that does the rounding
and an arch-specific function that returns the page size.  Can you send
a patch to implement this?

Thanks,

Paolo