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Thu, 09 Jan 2025 01:10:21 -0800 (PST) Message-ID: <031ce31b-0ab5-4964-96eb-642fbea67bfb@suse.com> Date: Thu, 9 Jan 2025 10:10:20 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 04/18] x86/pv: introduce function to populate perdomain area and use it to map Xen GDT To: Roger Pau Monne Cc: Andrew Cooper , xen-devel@lists.xenproject.org References: <20250108142659.99490-1-roger.pau@citrix.com> <20250108142659.99490-5-roger.pau@citrix.com> Content-Language: en-US From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; 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 In-Reply-To: <20250108142659.99490-5-roger.pau@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 08.01.2025 15:26, Roger Pau Monne wrote: > The current code to update the Xen part of the GDT when running a PV guest > relies on caching the direct map address of all the L1 tables used to map the > GDT and LDT, so that entries can be modified. > > Introduce a new function that populates the per-domain region, either using the > recursive linear mappings when the target vCPU is the current one, or by > directly modifying the L1 table of the per-domain region. > > Using such function to populate per-domain addresses drops the need to keep a > reference to per-domain L1 tables previously used to change the per-domain > mappings. Well, yes. You now record MFNs instead. And you do so at the expense of about 100 lines of new code. I'm afraid I'm lacking justification for this price to be paid. > @@ -2219,11 +2219,9 @@ void __init trap_init(void) > init_ler(); > > /* Cache {,compat_}gdt_l1e now that physically relocation is done. */ > - this_cpu(gdt_l1e) = > - l1e_from_pfn(virt_to_mfn(boot_gdt), __PAGE_HYPERVISOR_RW); > + this_cpu(gdt_mfn) = _mfn(virt_to_mfn(boot_gdt)); > if ( IS_ENABLED(CONFIG_PV32) ) > - this_cpu(compat_gdt_l1e) = > - l1e_from_pfn(virt_to_mfn(boot_compat_gdt), __PAGE_HYPERVISOR_RW); > + this_cpu(compat_gdt_mfn) = _mfn(virt_to_mfn(boot_compat_gdt)); The comment's going stale this way. Jan