Re: [Xen-devel] [PATCH 4/4] x86/hyperv: L0 assisted TLB flush

[Jan Beulich <jbeulich@xxxxxxxx>]

On 12.02.2020 18:43, Roger Pau Monné wrote:
> On Wed, Feb 12, 2020 at 04:09:18PM +0000, Wei Liu wrote:
>> Implement L0 assisted TLB flush for Xen on Hyper-V. It takes advantage
>> of several hypercalls:
>>
>>  * HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST
>>  * HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX
>>  * HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE
>>  * HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX
>>
>> Pick the most efficient hypercalls available.
>>
>> Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>
>> ---
>>  xen/arch/x86/guest/hyperv/Makefile  |   1 +
>>  xen/arch/x86/guest/hyperv/private.h |   9 ++
>>  xen/arch/x86/guest/hyperv/tlb.c     | 172 +++++++++++++++++++++++++++-
>>  xen/arch/x86/guest/hyperv/util.c    |  72 ++++++++++++
>>  4 files changed, 253 insertions(+), 1 deletion(-)
>>  create mode 100644 xen/arch/x86/guest/hyperv/util.c
>>
>> diff --git a/xen/arch/x86/guest/hyperv/Makefile 
>> b/xen/arch/x86/guest/hyperv/Makefile
>> index 18902c33e9..0e39410968 100644
>> --- a/xen/arch/x86/guest/hyperv/Makefile
>> +++ b/xen/arch/x86/guest/hyperv/Makefile
>> @@ -1,2 +1,3 @@
>>  obj-y += hyperv.o
>>  obj-y += tlb.o
>> +obj-y += util.o
>> diff --git a/xen/arch/x86/guest/hyperv/private.h 
>> b/xen/arch/x86/guest/hyperv/private.h
>> index 78e52f74ce..311f060495 100644
>> --- a/xen/arch/x86/guest/hyperv/private.h
>> +++ b/xen/arch/x86/guest/hyperv/private.h
>> @@ -24,12 +24,21 @@
>>  
>>  #include <xen/cpumask.h>
>>  #include <xen/percpu.h>
>> +#include <xen/types.h>
>>  
>>  DECLARE_PER_CPU(void *, hv_input_page);
>>  DECLARE_PER_CPU(void *, hv_vp_assist);
>>  DECLARE_PER_CPU(uint32_t, hv_vp_index);
>>  
>> +static inline uint32_t hv_vp_index(int cpu)
> 
> unsigned int for cpu.

And also for the return type, as per my comment on patch 1.

>> --- a/xen/arch/x86/guest/hyperv/tlb.c
>> +++ b/xen/arch/x86/guest/hyperv/tlb.c
>> @@ -19,15 +19,185 @@
>>   * Copyright (c) 2020 Microsoft.
>>   */
>>  
>> +#include <xen/cpu.h>
>>  #include <xen/cpumask.h>
>>  #include <xen/errno.h>
>>  
>> +#include <asm/guest/hyperv.h>
>> +#include <asm/guest/hyperv-hcall.h>
>> +#include <asm/guest/hyperv-tlfs.h>
>> +
>>  #include "private.h"
>>  
>> +/*
>> + * It is possible to encode up to 4096 pages using the lower 12 bits
>> + * in an element of gva_list
>> + */
>> +#define HV_TLB_FLUSH_UNIT (4096 * PAGE_SIZE)
>> +#define ORDER_TO_BYTES(order) ((1ul << (order)) * PAGE_SIZE)
> 
> There are already some conversion functions in xen/mm.h
> (get_order_from_{bytes/pages}), maybe you could add a
> get_bytes_from_order helper there?

I don't think a macro (or helper function) is worthwhile here - we
don't have any in the various other places that do the same. The
above should be used inline, preferably in the simpler form of
PAGE_SIZE << order.

Jan

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