Re: [PATCH v6 01/12] misc/xenmicrocode: Upload a microcode blob to the hypervisor

From: Chao Gao <chao.gao@intel.com>
To: Sergey Dyasli <sergey.dyasli@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>, Ashok Raj <ashok.raj@intel.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	xen-devel@lists.xenproject.org,
	Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [PATCH v6 01/12] misc/xenmicrocode: Upload a microcode blob to the hypervisor
Date: Tue, 2 Apr 2019 10:26:08 +0800	[thread overview]
Message-ID: <20190402022606.GA11787@gao-cwp> (raw)
In-Reply-To: <eed77cc8-b7a6-7ecb-4d2d-2ba23b967108@citrix.com>

On Mon, Mar 25, 2019 at 09:38:21AM +0000, Sergey Dyasli wrote:
>On 11/03/2019 07:57, Chao Gao wrote:
>> This patch provides a tool for late microcode update.
>> 
>> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>> Signed-off-by: Chao Gao <chao.gao@intel.com>
>> ---
>>  tools/libxc/include/xenctrl.h |  1 +
>>  tools/libxc/xc_misc.c         | 20 ++++++++++
>>  tools/misc/Makefile           |  4 ++
>>  tools/misc/xenmicrocode.c     | 89 +++++++++++++++++++++++++++++++++++++++++++
>>  4 files changed, 114 insertions(+)
>>  create mode 100644 tools/misc/xenmicrocode.c
>> 
>> diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
>> index 31cdda7..c69699b 100644
>> --- a/tools/libxc/include/xenctrl.h
>> +++ b/tools/libxc/include/xenctrl.h
>> @@ -1245,6 +1245,7 @@ typedef uint32_t xc_node_to_node_dist_t;
>>  int xc_physinfo(xc_interface *xch, xc_physinfo_t *info);
>>  int xc_cputopoinfo(xc_interface *xch, unsigned *max_cpus,
>>                     xc_cputopo_t *cputopo);
>> +int xc_platform_op(xc_interface *xch, struct xen_platform_op *op);
>>  int xc_numainfo(xc_interface *xch, unsigned *max_nodes,
>>                  xc_meminfo_t *meminfo, uint32_t *distance);
>>  int xc_pcitopoinfo(xc_interface *xch, unsigned num_devs,
>> diff --git a/tools/libxc/xc_misc.c b/tools/libxc/xc_misc.c
>> index 5e6714a..061c7a5 100644
>> --- a/tools/libxc/xc_misc.c
>> +++ b/tools/libxc/xc_misc.c
>> @@ -226,6 +226,26 @@ int xc_physinfo(xc_interface *xch,
>>      return 0;
>>  }
>>  
>> +int xc_platform_op(xc_interface *xch, struct xen_platform_op *op)
>> +{
>> +    int ret = 0;
>> +    DECLARE_PLATFORM_OP;
>> +    DECLARE_HYPERCALL_BOUNCE(op, sizeof(*op), XC_HYPERCALL_BUFFER_BOUNCE_BOTH);
>
>So I've found that the bouncing in this function is not needed.
>In fact, it gets in a way when Xen is returning information via xen_platform_op.
>I ended up having only the single line in this function:
>
>	return do_platform_op(xch, op);
>
>Not sure how correct this is, but it seems to work for ucode application and
>XENPF_get_cpu_version.

You are right. The bounce buffer here is pointless, as do_platform_op()
creates bounce buffer anyhow. Will remove it.

Thanks
Chao

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