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Re: [PATCH] x86/shadow: sh_type_to_size[] needs L2H entry when HVM+PV32
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
- Date: Mon, 23 Jan 2023 12:30:36 +0000
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- Thread-topic: [PATCH] x86/shadow: sh_type_to_size[] needs L2H entry when HVM+PV32
On 23/01/2023 10:47 am, Jan Beulich wrote:
> On 23.01.2023 11:43, Andrew Cooper wrote:
>> On 23/01/2023 8:12 am, Jan Beulich wrote:
>>> While the table is used only when HVM=y, the table entry of course needs
>>> to be properly populated when also PV32=y. Fully removing the table
>>> entry we therefore wrong.
>>>
>>> Fixes: 1894049fa283 ("x86/shadow: L2H shadow type is PV32-only")
>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> Erm, why?
>>
>> The safety justification for the original patch was that this is HVM
>> only code. And it really is HVM only code - it's genuinely compiled out
>> for !HVM builds.
> Right, and we have logic taking care of the !HVM case. But that same
> logic uses this "HVM-only" table when HVM=y also for all PV types.
Ok - this is what needs fixing then.
This is a layering violation which has successfully tricked you into
making a buggy patch.
I'm unwilling to bet this will be the final time either... "this file
is HVM-only, therefore no PV paths enter it" is a reasonable
expectation, and should be true.
~Andrew
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