From: Jan Beulich <jbeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>,
"Ian Jackson" <iwj@xenproject.org>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v3][4.15] x86: mirror compat argument translation area for 32-bit PV
Date: Thu, 25 Feb 2021 13:58:28 +0100 [thread overview]
Message-ID: <2bbc398d-f389-1155-68ca-348ebfe8dfe7@suse.com> (raw)
In-Reply-To: <0e9b9e12-f3b5-971c-caf6-377c7c7c439a@citrix.com>
On 25.02.2021 13:52, Andrew Cooper wrote:
> On 25/02/2021 09:30, Jan Beulich wrote:
>> --- a/xen/include/asm-x86/config.h
>> +++ b/xen/include/asm-x86/config.h
>> @@ -170,7 +170,11 @@ extern unsigned char boot_edid_info[128]
>> * Guest-defined use.
>> * 0x00000000f5800000 - 0x00000000ffffffff [168MB, PML4:0]
>> * Read-only machine-to-phys translation table (GUEST ACCESSIBLE).
>> - * 0x0000000100000000 - 0x00007fffffffffff [128TB-4GB, PML4:0-255]
>> + * 0x0000000100000000 - 0x000001ffffffffff [2TB-4GB, PML4:0-3]
>> + * Unused / Reserved for future use.
>> + * 0x0000020000000000 - 0x0000027fffffffff [512GB, 2^39 bytes, PML4:4]
>> + * Mirror of per-domain mappings (for argument translation area; also HVM).
>> + * 0x0000028000000000 - 0x00007fffffffffff [125.5TB, PML4:5-255]
>> * Unused / Reserved for future use.
>> */
>>
>> @@ -207,6 +211,8 @@ extern unsigned char boot_edid_info[128]
>> #define PERDOMAIN_SLOTS 3
>> #define PERDOMAIN_VIRT_SLOT(s) (PERDOMAIN_VIRT_START + (s) * \
>> (PERDOMAIN_SLOT_MBYTES << 20))
>> +/* Slot 4: mirror of per-domain mappings (for compat xlat area accesses). */
>> +#define PERDOMAIN_ALT_VIRT_START PML4_ADDR(260 % 256)
>
> 4.
>
> 260 % 256 is pure obfuscation.
Well, that's why the comment is there. The expression is to
show why 4 isn't entirely arbitrary. But well, if there's no
way to get this in without changing to 4, I will of course do
so. Before I submit v4 - are there any other concerns?
Jan
prev parent reply other threads:[~2021-02-25 12:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-25 9:30 [PATCH v3][4.15] x86: mirror compat argument translation area for 32-bit PV Jan Beulich
2021-02-25 9:32 ` Jan Beulich
2021-02-25 12:52 ` Andrew Cooper
2021-02-25 12:58 ` Jan Beulich [this message]
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