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Re: [XEN][PATCH] x86/paging: replace !paging_mode_hap() with paging_mode_shadow()
- To: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 17 Nov 2025 10:47:31 +0100
- Autocrypt: addr=jbeulich@xxxxxxxx; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL
- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Jason Andryuk <jason.andryuk@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 17 Nov 2025 09:47:36 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 15.11.2025 00:21, Jason Andryuk wrote:
> On 2025-11-14 09:44, Grygorii Strashko wrote:
>> From: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
>>
>> Now Xen supports only two paging modes: HAP and SHADOW, so
>> !paging_mode_hap() is actually means paging_mode_shadow().
For HVM, that is. For PV both could produce "false". Luckily the code
changes are all in line with that, but somewhere this detail wants
mentioning imo (as it's also not part of the patch subject). Happy to
make a small adjustment while committing; then ...
>> For an abstract, future case of there being a 3rd paging mode it is also
>> better to explicitly mention checked paging mode (SHADOW) instead of using
>> negative check of another paging mode (HAP).
>>
>> Hence, s/!paging_mode_hap()/paging_mode_shadow() which also allows DCE drop
>> unused code when SHADOW_PAGING=n.
>> The !paging_mode_hap() in hap.c not changed as HAP is checking for itself
>> to be enabled.
>>
>> Inspired by [1].
>>
>> [1]
>> https://patchwork.kernel.org/project/xen-devel/patch/20251111200958.3576341-3-grygorii_strashko@xxxxxxxx/
>> Signed-off-by: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
>
> Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Jan
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