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Re: [PATCH 6/8] x86: Derive XEN_MSR_PAT from its individual entries
- To: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 6 Dec 2022 12:43:22 +0100
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- Cc: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxx>, "Tim (Xen.org)" <tim@xxxxxxx>, Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 06 Dec 2022 11:43:33 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 06.12.2022 12:32, Andrew Cooper wrote:
> On 06/12/2022 04:33, Demi Marie Obenour wrote:
>> --- a/xen/arch/x86/include/asm/processor.h
>> +++ b/xen/arch/x86/include/asm/processor.h
>> @@ -92,13 +92,33 @@
>> X86_EFLAGS_NT|X86_EFLAGS_DF|X86_EFLAGS_IF| \
>> X86_EFLAGS_TF)
>>
>> +/* Individual entries in IA32_CR_PAT */
>> +#define MSR_PAT_UC _AC(0x00, ULL)
>> +#define MSR_PAT_WC _AC(0x01, ULL)
>> +#define MSR_PAT_RESERVED_1 _AC(0x02, ULL)
>> +#define MSR_PAT_RESERVED_2 _AC(0x03, ULL)
>> +#define MSR_PAT_WT _AC(0x04, ULL)
>> +#define MSR_PAT_WP _AC(0x05, ULL)
>> +#define MSR_PAT_WB _AC(0x06, ULL)
>> +#define MSR_PAT_UCM _AC(0x07, ULL)
>
> This isn't really correct. Constants for MSRs typically live in
> msr-index.h, but these are architectural x86 memory types.
>
> These ought be
>
> #define X86_MT_$X ... (skipping the two reserved values)
>
> in x86-defns.h, and the PAT_TYPE_*, MTRR_TYPE_* and EPT_EMT_* constants
> want removing.
>
> There are two minor restrictions (EPT can't have UCM, MTRR can't have
> WC), but they are all operating in terms of architectural memory type
> values, and the code ought to reflect this.
The unavailability of UCM is common to MTRR and EPT's EMT. WC, at the
same time, is a valid type to use in both. Which makes sense - EMT
after all merely is replacing what otherwise is expressed by MTRRs.
Jan
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